Android Input系统的启动以及Input场景下的ANR

为了分析Input场景下ANR发生的原因，特意找了对Input系统全面介绍的一篇文章，如果系统对于Input Event超过预定时间(5s)没有响应，则会弹出ANR提示用户继续等待或者选择FC。通过下面文章对Input事件传递流程的分析，在InputDispatcher.cpp里面会对持有分发锁有一个超时时间(3s)，在WMS中才是对事件真正开始计时。

• InputDispatching Timeout: 输入事件分发超时5s，包括按键和触摸事件。

原文地址：http://gityuan.com/2016/07/02/android-anr/

一. 概述

先简单总结和回顾以下前几篇文章的内容：

• Input系统—InputReader线程：通过EventHub从/dev/input节点获取事件，转换成EventEntry事件加入到InputDispatcher的mInboundQueue。
• Input系统—InputDispatcher线程：从mInboundQueue队列取出事件，转换成DispatchEntry事件加入到connection的outboundQueue队列。再然后开始处理分发事件，取出outbound队列，放入waitQueue.
• Input系统—UI线程：创建socket pair，分别位于”InputDispatcher”线程和focused窗口所在进程的UI主线程，可相互通信。
  • UI主线程：通过setFdEvents()， 监听socket客户端，收到消息后回调NativeInputEventReceiver();【见小节2.1】
  • “InputDispatcher”线程： 通过IMS.registerInputChannel()，监听socket服务端，收到消息后回调handleReceiveCallback；【见小节3.1】

接下来，以按键事件为例，说一说一次事件处理过程是如何完成。按键事件经过InputReader，再到InputDispatcher的startDispatchCycleLocked()过程会调用publishKeyEvent()，从该方法说起。

二. InputDispatcher线程

2.1 InputPublisher.publishKeyEvent

[-> InputTransport.cpp]

status_t InputPublisher::publishKeyEvent(...) {    if (!seq) {        return BAD_VALUE;    }    InputMessage msg;    msg.header.type = InputMessage::TYPE_KEY;    msg.body.key.seq = seq;    msg.body.key.deviceId = deviceId;    msg.body.key.source = source;    msg.body.key.action = action;    msg.body.key.flags = flags;    msg.body.key.keyCode = keyCode;    msg.body.key.scanCode = scanCode;    msg.body.key.metaState = metaState;    msg.body.key.repeatCount = repeatCount;    msg.body.key.downTime = downTime;    msg.body.key.eventTime = eventTime;    //通过InputChannel来发送消息    return mChannel->sendMessage(&msg);}

2.2 InputChannel.sendMessage

[-> InputTransport.cpp]

status_t InputChannel::sendMessage(const InputMessage* msg) {    size_t msgLength = msg->size();    ssize_t nWrite;    do {        //向目标mFd写入消息，采用异步非阻塞方式        nWrite = ::send(mFd, msg, msgLength, MSG_DONTWAIT | MSG_NOSIGNAL);    } while (nWrite == -1 && errno == EINTR);    if (nWrite < 0) {        int error = errno;        if (error == EAGAIN || error == EWOULDBLOCK) {            return WOULD_BLOCK;        }        if (error == EPIPE || error == ENOTCONN || error == ECONNREFUSED || error == ECONNRESET) {            return DEAD_OBJECT;        }        return -error;    }    if (size_t(nWrite) != msgLength) {        return DEAD_OBJECT;    }    return OK;}

Input系统—UI线程讲解了会创建socket pair，用于两个进程的线程间相互通信。当mFd写入消息后，此时会唤醒处于epoll_wait状态的应用进程的UI线程，见下文。

另外，当写入失败，则返回值为WOULD_BLOCK或者DEAD_OBJECT。

三. UI主线程

当收到消息的处理过程，Android消息机制在获取下一条消息的时候,会调用lnativePollOnce(),最终进入到Looper::pollInner()过程，如下：

3.1 Looper::pollInner

int Looper::pollInner(int timeoutMillis) {    ...    int result = POLL_WAKE;    mResponses.clear();    mResponseIndex = 0;    mPolling = true; //即将处于idle状态    struct epoll_event eventItems[EPOLL_MAX_EVENTS]; //fd最大个数为16    //等待事件发生或者超时，在nativeWake()方法，向管道写端写入字符;    int eventCount = epoll_wait(mEpollFd, eventItems, EPOLL_MAX_EVENTS, timeoutMillis);    mPolling = false; //不再处于idle状态    mLock.lock();  //请求锁    ...    //循环遍历，处理所有的事件    for (int i = 0; i < eventCount; i++) {        int fd = eventItems[i].data.fd;        uint32_t epollEvents = eventItems[i].events;        if (fd == mWakeEventFd) {            if (epollEvents & EPOLLIN) {                awoken(); //已唤醒则读取并清空管道数据            }        } else {            ssize_t requestIndex = mRequests.indexOfKey(fd);            if (requestIndex >= 0) {                int events = 0;                if (epollEvents & EPOLLIN) events |= EVENT_INPUT;                if (epollEvents & EPOLLOUT) events |= EVENT_OUTPUT;                if (epollEvents & EPOLLERR) events |= EVENT_ERROR;                if (epollEvents & EPOLLHUP) events |= EVENT_HANGUP;                //处理request，生成对应的reponse对象，push到mResponses数组                pushResponse(events, mRequests.valueAt(requestIndex));            }        }    }Done: ;    //再处理Native的Message，调用相应回调方法    while (mMessageEnvelopes.size() != 0) {        nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);        //取出消息        const MessageEnvelope& messageEnvelope = mMessageEnvelopes.itemAt(0);        if (messageEnvelope.uptime <= now) {            sp<MessageHandler> handler = messageEnvelope.handler;            Message message = messageEnvelope.message;            mMessageEnvelopes.removeAt(0); //移除该消息            mLock.unlock();            handler->handleMessage(message);  // 处理消息事件        }        mLock.lock();        ...    }    mLock.unlock(); //释放锁    //处理带有Callback()方法的Response事件，执行Reponse相应的回调方法    for (size_t i = 0; i < mResponses.size(); i++) {        Response& response = mResponses.editItemAt(i);        if (response.request.ident == POLL_CALLBACK) {            int fd = response.request.fd;            int events = response.events;            void* data = response.request.data;            // 处理请求的回调方法【见小节3.2】            int callbackResult = response.request.callback->handleEvent(fd, events, data);            if (callbackResult == 0) {                removeFd(fd, response.request.seq); //移除fd            }            response.request.callback.clear(); //清除reponse引用的回调方法            result = POLL_CALLBACK;  // 发生回调        }    }    return result;}

此处response.request.callback是指NativeInputEventReceiver，接下来便是执行NativeInputEventReceiver.handleEvent();

3.2 handleEvent

[-> android_view_InputEventReceiver.cpp]

int NativeInputEventReceiver::handleEvent(int receiveFd, int events, void* data) {    if (events & (ALOOPER_EVENT_ERROR | ALOOPER_EVENT_HANGUP)) {        return 0;  //移除窗口或者IME对话框， 则移除该事件    }    if (events & ALOOPER_EVENT_INPUT) {        JNIEnv* env = AndroidRuntime::getJNIEnv();        //【见小节3.3】        status_t status = consumeEvents(env, false /*consumeBatches*/, -1, NULL);        mMessageQueue->raiseAndClearException(env, "handleReceiveCallback");        return status == OK || status == NO_MEMORY ? 1 : 0;    }    if (events & ALOOPER_EVENT_OUTPUT) {        for (size_t i = 0; i < mFinishQueue.size(); i++) {            const Finish& finish = mFinishQueue.itemAt(i);            //【见小节3.4】            status_t status = mInputConsumer.sendFinishedSignal(finish.seq, finish.handled);            if (status) {                mFinishQueue.removeItemsAt(0, i);                if (status == WOULD_BLOCK) {                    return 1; //保留callback，稍后重试                }                if (status != DEAD_OBJECT) {                    JNIEnv* env = AndroidRuntime::getJNIEnv();                    String8 message;                    message.appendFormat("Failed to finish input event.  status=%d", status);                    jniThrowRuntimeException(env, message.string());                    mMessageQueue->raiseAndClearException(env, "finishInputEvent");                }                return 0; //移除callback            }        }        mFinishQueue.clear();        setFdEvents(ALOOPER_EVENT_INPUT);        return 1;    }    return 1;}

UI线程收到Key事件后，开始处理该事件。

3.3 NativeInputEventReceiver.consumeEvents

[-> android_view_InputEventReceiver.cpp]

status_t NativeInputEventReceiver::consumeEvents(JNIEnv* env,        bool consumeBatches, nsecs_t frameTime, bool* outConsumedBatch) {    ...    ScopedLocalRef<jobject> receiverObj(env, NULL);    bool skipCallbacks = false;    for (;;) {        uint32_t seq;        InputEvent* inputEvent;        //【见小节3.3.1】        status_t status = mInputConsumer.consume(&mInputEventFactory,                consumeBatches, frameTime, &seq, &inputEvent);        if (status) {            if (status == WOULD_BLOCK) {                ...                return OK; //消费完成            }            return status; //消失失败        }        if (!skipCallbacks) {            if (!receiverObj.get()) {                receiverObj.reset(jniGetReferent(env, mReceiverWeakGlobal));                if (!receiverObj.get()) {                    return DEAD_OBJECT;                }            }            jobject inputEventObj;            switch (inputEvent->getType()) {                case AINPUT_EVENT_TYPE_KEY:                    //由Native的inputEvent来生成Java层的事件                    inputEventObj = android_view_KeyEvent_fromNative(env,                            static_cast<KeyEvent*>(inputEvent));                    break;                ...            }            if (inputEventObj) {                //执行Java层的InputEventReceiver.dispachInputEvent【见小节3.3.3】                env->CallVoidMethod(receiverObj.get(),                        gInputEventReceiverClassInfo.dispatchInputEvent, seq, inputEventObj);                if (env->ExceptionCheck()) {                    skipCallbacks = true; //分发过程发生异常                }                env->DeleteLocalRef(inputEventObj);            } else {                skipCallbacks = true;            }        }        if (skipCallbacks) {            //发生异常，则直接向InputDispatcher线程发送完成信号。            mInputConsumer.sendFinishedSignal(seq, false);        }    }}

3.3.1 InputConsumer.consume

[->InputTransport.cpp ::InputConsumer]

status_t InputConsumer::consume(InputEventFactoryInterface* factory,        bool consumeBatches, nsecs_t frameTime, uint32_t* outSeq, InputEvent** outEvent) {    *outSeq = 0;    *outEvent = NULL;    //循环遍历所有的Event    while (!*outEvent) {        if (mMsgDeferred) {            mMsgDeferred = false; //上一次没有处理的消息        } else {            //收到新消息【见小节3.3.2】            status_t result = mChannel->receiveMessage(&mMsg);            if (result) {                if (consumeBatches || result != WOULD_BLOCK) {                    result = consumeBatch(factory, frameTime, outSeq, outEvent);                    if (*outEvent) {                        break;                    }                }                return result;            }        }        switch (mMsg.header.type) {          case InputMessage::TYPE_KEY: {              //从mKeyEventPool池中取出KeyEvent              KeyEvent* keyEvent = factory->createKeyEvent();              if (!keyEvent) return NO_MEMORY;              //将msg封装成KeyEvent              initializeKeyEvent(keyEvent, &mMsg);              *outSeq = mMsg.body.key.seq;              *outEvent = keyEvent;              break;          }          ...        }    }    return OK;}

3.3.2 InputChannel.receiveMessage

[-> InputTransport.cpp]

status_t InputChannel::receiveMessage(InputMessage* msg) {    ssize_t nRead;    do {        //读取InputDispatcher发送过来的消息        nRead = ::recv(mFd, msg, sizeof(InputMessage), MSG_DONTWAIT);    } while (nRead == -1 && errno == EINTR);    if (nRead < 0) {        int error = errno;        if (error == EAGAIN || error == EWOULDBLOCK) {            return WOULD_BLOCK;        }        if (error == EPIPE || error == ENOTCONN || error == ECONNREFUSED) {            return DEAD_OBJECT;        }        return -error;    }    if (nRead == 0) {        return DEAD_OBJECT;    }    if (!msg->isValid(nRead)) {        return BAD_VALUE;    }    return OK;}

3.3.3 InputEventReceiver.dispachInputEvent

[-> InputEventReceiver.java]

private void dispatchInputEvent(int seq, InputEvent event) {    mSeqMap.put(event.getSequenceNumber(), seq);    onInputEvent(event); //[见小节3.3.4]}

3.3.4 onInputEvent

[-> ViewRootImpl.java ::WindowInputEventReceiver]

final class WindowInputEventReceiver extends InputEventReceiver {    public void onInputEvent(InputEvent event) {       enqueueInputEvent(event, this, 0, true); //【见小节3.3.5】    }    ...}

3.3.5 enqueueInputEvent

[-> ViewRootImpl.java]

void enqueueInputEvent(InputEvent event,        InputEventReceiver receiver, int flags, boolean processImmediately) {    adjustInputEventForCompatibility(event);    QueuedInputEvent q = obtainQueuedInputEvent(event, receiver, flags);    QueuedInputEvent last = mPendingInputEventTail;    if (last == null) {        mPendingInputEventHead = q;        mPendingInputEventTail = q;    } else {        last.mNext = q;        mPendingInputEventTail = q;    }    mPendingInputEventCount += 1;    if (processImmediately) {        doProcessInputEvents(); //【见小节3.3.6】    } else {        scheduleProcessInputEvents();    }}

3.3.6 doProcessInputEvents

[-> ViewRootImpl.java]

void doProcessInputEvents() {    while (mPendingInputEventHead != null) {        QueuedInputEvent q = mPendingInputEventHead;        mPendingInputEventHead = q.mNext;        if (mPendingInputEventHead == null) {            mPendingInputEventTail = null;        }        q.mNext = null;        mPendingInputEventCount -= 1;        long eventTime = q.mEvent.getEventTimeNano();        long oldestEventTime = eventTime;        ...        mChoreographer.mFrameInfo.updateInputEventTime(eventTime, oldestEventTime);        //[见小节3.3.7]        deliverInputEvent(q);    }    if (mProcessInputEventsScheduled) {        mProcessInputEventsScheduled = false;        mHandler.removeMessages(MSG_PROCESS_INPUT_EVENTS);    }}

3.3.7 事件分发

[-> ViewRootImpl.java]

private void deliverInputEvent(QueuedInputEvent q) {     if (mInputEventConsistencyVerifier != null) {         mInputEventConsistencyVerifier.onInputEvent(q.mEvent, 0);     }     InputStage stage;     if (q.shouldSendToSynthesizer()) {         stage = mSyntheticInputStage;     } else {         stage = q.shouldSkipIme() ? mFirstPostImeInputStage : mFirstInputStage;     }     if (stage != null) {         stage.deliver(q);     } else {         finishInputEvent(q); //[见小节3.4]     } }

经过一系列的InputStage调用, 最终会分发到真正需要处理该时间的窗口. 当处理完后会调用finishInputEvent(), 见小节3.4

3.4 finishInputEvent

[-> ViewRootImpl.java]

 private void finishInputEvent(QueuedInputEvent q) {    if (q.mReceiver != null) {        boolean handled = (q.mFlags & QueuedInputEvent.FLAG_FINISHED_HANDLED) != 0;        //[见小节3.4.1]        q.mReceiver.finishInputEvent(q.mEvent, handled);    } else {        q.mEvent.recycleIfNeededAfterDispatch();    }    recycleQueuedInputEvent(q);}

3.4.1 mReceiver.finishInputEvent

public final void finishInputEvent(InputEvent event, boolean handled) {    if (mReceiverPtr == 0) {        ...    } else {        int index = mSeqMap.indexOfKey(event.getSequenceNumber());        if (index < 0) {            ...        } else {            int seq = mSeqMap.valueAt(index);            mSeqMap.removeAt(index);            //经过层层调用,见[小节3.5]            nativeFinishInputEvent(mReceiverPtr, seq, handled);        }    }    event.recycleIfNeededAfterDispatch();}

3.5 sendFinishedSignal

[-> InputTransport.cpp ::InputConsumer]

status_t InputConsumer::sendFinishedSignal(uint32_t seq, bool handled) {    ...    size_t seqChainCount = mSeqChains.size();    if (seqChainCount) {        uint32_t currentSeq = seq;        uint32_t chainSeqs[seqChainCount];        size_t chainIndex = 0;        for (size_t i = seqChainCount; i-- > 0; ) {             const SeqChain& seqChain = mSeqChains.itemAt(i);             if (seqChain.seq == currentSeq) {                 currentSeq = seqChain.chain;                 chainSeqs[chainIndex++] = currentSeq;                 mSeqChains.removeAt(i);             }        }        status_t status = OK;        while (!status && chainIndex-- > 0) {            //[见小节3.5.1]            status = sendUnchainedFinishedSignal(chainSeqs[chainIndex], handled);        }        if (status) {            // An error occurred so at least one signal was not sent, reconstruct the chain.            do {                SeqChain seqChain;                seqChain.seq = chainIndex != 0 ? chainSeqs[chainIndex - 1] : seq;                seqChain.chain = chainSeqs[chainIndex];                mSeqChains.push(seqChain);            } while (chainIndex-- > 0);            return status;        }    }    return sendUnchainedFinishedSignal(seq, handled);}

3.5.1 sendUnchainedFinishedSignal

[-> InputTransport.cpp ::InputConsumer]

status_t InputConsumer::sendUnchainedFinishedSignal(uint32_t seq, bool handled) {    InputMessage msg;    msg.header.type = InputMessage::TYPE_FINISHED;    msg.body.finished.seq = seq;    msg.body.finished.handled = handled;    return mChannel->sendMessage(&msg);}

通过InputChannel->sendMessage，将TYPE_FINISHED类型的消息，发送回InputDispatcher线程。

四. InputDispatcher线程

4.1 Looper::pollInner

int Looper::pollInner(int timeoutMillis) {    int eventCount = epoll_wait(mEpollFd, eventItems, EPOLL_MAX_EVENTS, timeoutMillis);    ...Done:    ...    for (size_t i = 0; i < mResponses.size(); i++) {        Response& response = mResponses.editItemAt(i);        if (response.request.ident == POLL_CALLBACK) {            int fd = response.request.fd;            int events = response.events;            void* data = response.request.data;            // 处理请求的回调方法【见小节4.2】            int callbackResult = response.request.callback->handleEvent(fd, events, data);            ...        }    }    return result;}

此处response.request.callback是指SimpleLooperCallback。接下来调用SimpleLooperCallback.handleEvent(). 执行后的返回值callbackResult=0则移除该fd，否则稍后重新尝试。

4.2 handleEvent

[-> Looper.cpp ::SimpleLooperCallback]

SimpleLooperCallback::SimpleLooperCallback(Looper_callbackFunc callback) :        mCallback(callback) {}int SimpleLooperCallback::handleEvent(int fd, int events, void* data) {    //handleReceiveCallback()【见小节4.3】    return mCallback(fd, events, data);}

IMS.registerInputChannel()过程，会调用Looper.addFd()完成的赋值操作，mCallback等于handleReceiveCallback()方法。

4.3 handleReceiveCallback

[-> InputDispatcher]

int InputDispatcher::handleReceiveCallback(int fd, int events, void* data) {    InputDispatcher* d = static_cast<InputDispatcher*>(data);    {        AutoMutex _l(d->mLock);        ssize_t connectionIndex = d->mConnectionsByFd.indexOfKey(fd);        bool notify;        sp<Connection> connection = d->mConnectionsByFd.valueAt(connectionIndex);        if (!(events & (ALOOPER_EVENT_ERROR | ALOOPER_EVENT_HANGUP))) {            ...            nsecs_t currentTime = now();            bool gotOne = false;            status_t status;            for (;;) {                uint32_t seq;                bool handled;                //【见小节4.4】                status = connection->inputPublisher.receiveFinishedSignal(&seq, &handled);                if (status) {                    break;                }                //【见小节4.5】                d->finishDispatchCycleLocked(currentTime, connection, seq, handled);                gotOne = true;            }            if (gotOne) {                d->runCommandsLockedInterruptible(); //执行命令【见小节4.6】                if (status == WOULD_BLOCK) {                    return 1;                }            }            notify = status != DEAD_OBJECT || !connection->monitor;        } else {            ...             //input channel被关闭或者发生错误        }        //取消注册channel        d->unregisterInputChannelLocked(connection->inputChannel, notify);        return 0;    }}

4.4 InputPublisher.receiveFinishedSignal

[-> InputTransport.cpp]

status_t InputPublisher::receiveFinishedSignal(uint32_t* outSeq, bool* outHandled) {    InputMessage msg;    //接收消息    status_t result = mChannel->receiveMessage(&msg);    if (result) {        *outSeq = 0;        *outHandled = false;        return result;    }    if (msg.header.type != InputMessage::TYPE_FINISHED) {        return UNKNOWN_ERROR; //发生错误    }    *outSeq = msg.body.finished.seq;    *outHandled = msg.body.finished.handled;    return OK;}

4.5 finishDispatchCycleLocked

[-> InputDispatcher.cpp]

void InputDispatcher::finishDispatchCycleLocked(nsecs_t currentTime,        const sp<Connection>& connection, uint32_t seq, bool handled) {    connection->inputPublisherBlocked = false;    if (connection->status == Connection::STATUS_BROKEN            || connection->status == Connection::STATUS_ZOMBIE) {        return;    }    //通知系统准备启动下一次分发流程【见小节4.5.1】    onDispatchCycleFinishedLocked(currentTime, connection, seq, handled);}

4.5.1 onDispatchCycleFinishedLocked

[-> InputDispatcher.cpp]

void InputDispatcher::onDispatchCycleFinishedLocked(        nsecs_t currentTime, const sp<Connection>& connection, uint32_t seq, bool handled) {    //向mCommandQueue添加命令    CommandEntry* commandEntry = postCommandLocked(            & InputDispatcher::doDispatchCycleFinishedLockedInterruptible);    commandEntry->connection = connection;    commandEntry->eventTime = currentTime;    commandEntry->seq = seq;    commandEntry->handled = handled;}

4.6 runCommandsLockedInterruptible

[-> InputDispatcher.cpp]

bool InputDispatcher::runCommandsLockedInterruptible() {    if (mCommandQueue.isEmpty()) {        return false;    }    do {        //从mCommandQueue队列的头部取出第一个元素【见小节4.6.1】        CommandEntry* commandEntry = mCommandQueue.dequeueAtHead();        Command command = commandEntry->command;        //此处调用的命令隐式地包含'LockedInterruptible'        (this->*command)(commandEntry);        commandEntry->connection.clear();        delete commandEntry;    } while (! mCommandQueue.isEmpty());    return true;}

由【小节4.5】，可以队列中的元素至少有doDispatchCycleFinishedLockedInterruptible。

4.6.1 doDispatchCycleFinishedLockedInterruptible

[-> InputDispatcher.cpp]

void InputDispatcher::doDispatchCycleFinishedLockedInterruptible(        CommandEntry* commandEntry) {    sp<Connection> connection = commandEntry->connection;    nsecs_t finishTime = commandEntry->eventTime;    uint32_t seq = commandEntry->seq;    bool handled = commandEntry->handled;    //获取分发事件    DispatchEntry* dispatchEntry = connection->findWaitQueueEntry(seq);    if (dispatchEntry) {        nsecs_t eventDuration = finishTime - dispatchEntry->deliveryTime;        //打印出所有分发时间超过2s的事件        if (eventDuration > SLOW_EVENT_PROCESSING_WARNING_TIMEOUT) {            String8 msg;            msg.appendFormat("Window '%s' spent %0.1fms processing the last input event: ",                    connection->getWindowName(), eventDuration * 0.000001f);            dispatchEntry->eventEntry->appendDescription(msg);            ALOGI("%s", msg.string());        }        bool restartEvent;        if (dispatchEntry->eventEntry->type == EventEntry::TYPE_KEY) {            KeyEntry* keyEntry = static_cast<KeyEntry*>(dispatchEntry->eventEntry);            restartEvent = afterKeyEventLockedInterruptible(connection,                    dispatchEntry, keyEntry, handled);        } else if (dispatchEntry->eventEntry->type == EventEntry::TYPE_MOTION) {            ...        } else {            ...        }        if (dispatchEntry == connection->findWaitQueueEntry(seq)) {            //将dispatchEntry事件从等待队列(waitQueue)中移除            connection->waitQueue.dequeue(dispatchEntry);            if (restartEvent && connection->status == Connection::STATUS_NORMAL) {                connection->outboundQueue.enqueueAtHead(dispatchEntry);            } else {                releaseDispatchEntryLocked(dispatchEntry);            }        }        //启动下一个事件处理循环。        startDispatchCycleLocked(now(), connection);    }}

该方法主要功能：

• 打印出所有分发时间超过2s的事件；
• 将dispatchEntry事件从等待队列(waitQueue)中移除；
• 启动下一个事件处理循环。

五. 总结

5.1 整体框架图

5.2 交互过程

用一张图来总结交互过程，主要是通过一对socket方式来通信。 当input时间分发到app端, 那么便进入来了InputEventReceiver.dispatchInputEvent()过程.

图解:

1. InputDispatcher线程调用InputPublisher的publishKeyEvent向UI主线程发送input事件;
2. UI主线程接收到该事件后,调用InputConsumer的consumeEvents来处理该事件, 一路执行到ViewRootImpl.deliverInputEvent()方法;
3. UI主线程经过一系列的InputStage来处理, 当事件分发完成,则会执行finishInputEvent()方法.再进一步调用InputConsumer::sendFinishedSignal 告知InputDispatcher线程该时事件已处理完成.
4. InputDispatcher线程收到该事件后, 执行InputDispatcher::handleReceiveCallback();最终会调用doDispatchCycleFinishedLockedInterruptible()方法 ,将dispatchEntry事件从等待队列(waitQueue)中移除.

基于Android 6.0源码， 分析InputManagerService的启动过程

frameworks/native/services/inputflinger/  - InputDispatcher.cpp  - InputReader.cpp  - InputManager.cpp  - EventHub.cpp  - InputListener.cppframeworks/native/libs/input/  - InputTransport.cpp  - Input.cpp  - InputDevice.cpp  - Keyboard.cpp  - KeyCharacterMap.cpp  - IInputFlinger.cppframeworks/base/services/core/  - java/com/android/server/input/InputManagerService.java  - jni/com_android_server_input_InputManagerService.cpp

一. 概述

当用户触摸屏幕或者按键操作，首次触发的是硬件驱动，驱动收到事件后，将该相应事件写入到输入设备节点， 这便产生了最原生态的内核事件。接着，输入系统取出原生态的事件，经过层层封装后成为KeyEvent或者MotionEvent ；最后，交付给相应的目标窗口(Window)来消费该输入事件。可见，输入系统在整个过程起到承上启下的衔接作用。

Input模块的主要组成：

• Native层的InputReader负责从EventHub取出事件并处理，再交给InputDispatcher；
• Native层的InputDispatcher接收来自InputReader的输入事件，并记录WMS的窗口信息，用于派发事件到合适的窗口；
• Java层的InputManagerService跟WMS交互，WMS记录所有窗口信息，并同步更新到IMS，为InputDispatcher正确派发事件到ViewRootImpl提供保障；

Input相关的动态库：

• libinputflinger.so：frameworks/native/services/inputflinger/
• libinputservice.so：frameworks/base/libs/input/
• libinput.so： frameworks/native/libs/input/

1.1 整体框架类图

InputManagerService作为system_server中的重要服务，继承于IInputManager.Stub， 作为Binder服务端，那么Client位于InputManager的内部通过IInputManager.Stub.asInterface() 获取Binder代理端，C/S两端通信的协议是由IInputManager.aidl来定义的。

Input模块所涉及的重要类的关系如下：

图解:

• InputManagerService位于Java层的InputManagerService.java文件；
  • 其成员mPtr指向Native层的NativeInputManager对象；
• NativeInputManager位于Native层的com_android_server_input_InputManagerService.cpp文件；
  • 其成员mServiceObj指向Java层的IMS对象；
  • 其成员mLooper是指“android.display”线程的Looper;
• InputManager位于libinputflinger中的InputManager.cpp文件；
  • InputDispatcher和InputReader的成员变量mPolicy都是指NativeInputManager对象;
  • InputReader的成员mQueuedListener，数据类型为QueuedInputListener；通过其内部成员变量mInnerListener指向InputDispatcher对象； 这便是InputReader跟InputDispatcher交互的中间枢纽。

1.2 启动调用栈

IMS服务是伴随着system_server进程的启动而启动，整个调用过程：

InputManagerService(初始化)    nativeInit        NativeInputManager            EventHub            InputManager                InputDispatcher                    Looper                InputReader                    QueuedInputListener                InputReaderThread                InputDispatcherThreadIMS.start(启动)    nativeStart        InputManager.start            InputReaderThread->run            InputDispatcherThread->run

整个过程首先创建如下对象：NativeInputManager，EventHub，InputManager， InputDispatcher，InputReader，InputReaderThread，InputDispatcherThread。 接着便是启动两个工作线程InputReader,InputDispatcher。

二. 启动过程

private void startOtherServices() {    //初始化IMS对象【见小节2.1】    inputManager = new InputManagerService(context);    ServiceManager.addService(Context.INPUT_SERVICE, inputManager);    ...    //将InputMonitor对象保持到IMS对象    inputManager.setWindowManagerCallbacks(wm.getInputMonitor());    //[见小节2.9]    inputManager.start();}

2.1 InputManagerService

[-> InputManagerService.java]

public InputManagerService(Context context) {     this.mContext = context;     // 运行在线程"android.display"     this.mHandler = new InputManagerHandler(DisplayThread.get().getLooper());     ...     //初始化native对象【见小节2.2】     mPtr = nativeInit(this, mContext, mHandler.getLooper().getQueue());     LocalServices.addService(InputManagerInternal.class, new LocalService()); }

2.2 nativeInit

[-> com_android_server_input_InputManagerService.cpp]

static jlong nativeInit(JNIEnv* env, jclass /* clazz */,        jobject serviceObj, jobject contextObj, jobject messageQueueObj) {    //获取native消息队列    sp<MessageQueue> messageQueue = android_os_MessageQueue_getMessageQueue(env, messageQueueObj);    ...    //创建Native的InputManager【见小节2.3】    NativeInputManager* im = new NativeInputManager(contextObj, serviceObj,            messageQueue->getLooper());    im->incStrong(0);    return reinterpret_cast<jlong>(im); //返回Native对象的指针}

2.3 NativeInputManager

[-> com_android_server_input_InputManagerService.cpp]

NativeInputManager::NativeInputManager(jobject contextObj,        jobject serviceObj, const sp<Looper>& looper) :        mLooper(looper), mInteractive(true) {    JNIEnv* env = jniEnv();    mContextObj = env->NewGlobalRef(contextObj); //上层IMS的context    mServiceObj = env->NewGlobalRef(serviceObj); //上层IMS对象    ...    sp<EventHub> eventHub = new EventHub(); // 创建EventHub对象【见小节2.4】    mInputManager = new InputManager(eventHub, this, this); // 创建InputManager对象【见小节2.5】}

此处的mLooper是指“android.display”线程的Looper; libinputservice.so库中PointerController和SpriteController对象都继承于于MessageHandler， 这两个Handler采用的便是该mLooper.

2.4 EventHub

[-> EventHub.cpp]

EventHub::EventHub(void) :        mBuiltInKeyboardId(NO_BUILT_IN_KEYBOARD), mNextDeviceId(1), mControllerNumbers(),        mOpeningDevices(0), mClosingDevices(0),        mNeedToSendFinishedDeviceScan(false),        mNeedToReopenDevices(false), mNeedToScanDevices(true),        mPendingEventCount(0), mPendingEventIndex(0), mPendingINotify(false) {    acquire_wake_lock(PARTIAL_WAKE_LOCK, WAKE_LOCK_ID);    //创建epoll    mEpollFd = epoll_create(EPOLL_SIZE_HINT);    mINotifyFd = inotify_init();    //此处DEVICE_PATH为"/dev/input"，监听该设备路径    int result = inotify_add_watch(mINotifyFd, DEVICE_PATH, IN_DELETE | IN_CREATE);    struct epoll_event eventItem;    memset(&eventItem, 0, sizeof(eventItem));    eventItem.events = EPOLLIN;    eventItem.data.u32 = EPOLL_ID_INOTIFY;    //添加INotify到epoll实例    result = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, mINotifyFd, &eventItem);    int wakeFds[2];    result = pipe(wakeFds); //创建管道    mWakeReadPipeFd = wakeFds[0];    mWakeWritePipeFd = wakeFds[1];    //将pipe的读和写都设置为非阻塞方式    result = fcntl(mWakeReadPipeFd, F_SETFL, O_NONBLOCK);    result = fcntl(mWakeWritePipeFd, F_SETFL, O_NONBLOCK);    eventItem.data.u32 = EPOLL_ID_WAKE;    //添加管道的读端到epoll实例    result = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, mWakeReadPipeFd, &eventItem);    ...}

该方法主要功能：

• 初始化INotify（监听”/dev/input”），并添加到epoll实例
• 创建非阻塞模式的管道，并添加到epoll;

2.5 InputManager

[-> InputManager.cpp]

InputManager::InputManager(        const sp<EventHubInterface>& eventHub,        const sp<InputReaderPolicyInterface>& readerPolicy,        const sp<InputDispatcherPolicyInterface>& dispatcherPolicy) {    //创建InputDispatcher对象【见小节2.6】    mDispatcher = new InputDispatcher(dispatcherPolicy);    //创建InputReader对象【见小节2.7】    mReader = new InputReader(eventHub, readerPolicy, mDispatcher);    initialize();//【见小节2.8】}

InputDispatcher和InputReader的mPolicy成员变量都是指NativeInputManager对象。

2.6 InputDispatcher

[-> InputDispatcher.cpp]

InputDispatcher::InputDispatcher(const sp<InputDispatcherPolicyInterface>& policy) :    mPolicy(policy),    mPendingEvent(NULL), mLastDropReason(DROP_REASON_NOT_DROPPED),    mAppSwitchSawKeyDown(false), mAppSwitchDueTime(LONG_LONG_MAX),    mNextUnblockedEvent(NULL),    mDispatchEnabled(false), mDispatchFrozen(false), mInputFilterEnabled(false),    mInputTargetWaitCause(INPUT_TARGET_WAIT_CAUSE_NONE) {    //创建Looper对象    mLooper = new Looper(false);    mKeyRepeatState.lastKeyEntry = NULL;    //获取分发超时参数    policy->getDispatcherConfiguration(&mConfig);}

该方法主要工作：

• 创建属于自己线程的Looper对象；
• 超时参数来自于IMS，参数默认值keyRepeatTimeout = 500，keyRepeatDelay = 50。

2.7 InputReader

[-> InputReader.cpp]

InputReader::InputReader(const sp<EventHubInterface>& eventHub,        const sp<InputReaderPolicyInterface>& policy,        const sp<InputListenerInterface>& listener) :        mContext(this), mEventHub(eventHub), mPolicy(policy),        mGlobalMetaState(0), mGeneration(1),        mDisableVirtualKeysTimeout(LLONG_MIN), mNextTimeout(LLONG_MAX),        mConfigurationChangesToRefresh(0) {    // 创建输入监听对象    mQueuedListener = new QueuedInputListener(listener);    {        AutoMutex _l(mLock);        refreshConfigurationLocked(0);        updateGlobalMetaStateLocked();    }}

此处mQueuedListener的成员变量mInnerListener便是InputDispatcher对象。 前面【小节2.5】InputManager创建完InputDispatcher和InputReader对象， 接下里便是调用initialize初始化。

2.8 initialize

[-> InputManager.cpp]

void InputManager::initialize() {    //创建线程“InputReader”    mReaderThread = new InputReaderThread(mReader);    //创建线程”InputDispatcher“    mDispatcherThread = new InputDispatcherThread(mDispatcher);}InputReaderThread::InputReaderThread(const sp<InputReaderInterface>& reader) :        Thread(/*canCallJava*/ true), mReader(reader) {}InputDispatcherThread::InputDispatcherThread(const sp<InputDispatcherInterface>& dispatcher) :        Thread(/*canCallJava*/ true), mDispatcher(dispatcher) {}

初始化的主要工作就是创建两个能访问Java代码的native线程。

• 创建线程“InputReader”
• 创建线程”InputDispatcher“

到此[2.1-2.8]整个的InputManagerService对象初始化过程并完成，接下来便是调用其start方法。

2.9 IMS.start

[-> InputManagerService.java]

public void start() {    // 启动native对象[见小节2.10]    nativeStart(mPtr);    Watchdog.getInstance().addMonitor(this);    //注册触摸点速度和是否显示功能的观察者    registerPointerSpeedSettingObserver();    registerShowTouchesSettingObserver();    mContext.registerReceiver(new BroadcastReceiver() {        @Override        public void onReceive(Context context, Intent intent) {            updatePointerSpeedFromSettings();            updateShowTouchesFromSettings();        }    }, new IntentFilter(Intent.ACTION_USER_SWITCHED), null, mHandler);    updatePointerSpeedFromSettings(); //更新触摸点的速度    updateShowTouchesFromSettings(); //是否在屏幕上显示触摸点}

2.10 nativeStart

[-> com_android_server_input_InputManagerService.cpp]

static void nativeStart(JNIEnv* env, jclass /* clazz */, jlong ptr) {    //此处ptr记录的便是NativeInputManager    NativeInputManager* im = reinterpret_cast<NativeInputManager*>(ptr);    // [见小节2.11]    status_t result = im->getInputManager()->start();    ...}

2.11 InputManager.start

[InputManager.cpp]

status_t InputManager::start() {    result = mDispatcherThread->run("InputDispatcher", PRIORITY_URGENT_DISPLAY);    result = mReaderThread->run("InputReader", PRIORITY_URGENT_DISPLAY);    ...    return OK;}

该方法的主要功能是启动两个线程:

• 启动线程“InputReader”
• 启动线程”InputDispatcher“

三. 总结

分层视角：

1. Java层InputManagerService：采用android.display线程处理Message.
2. JNI的NativeInputManager：采用android.display线程处理Message,以及创建EventHub。
3. Native的InputManager：创建InputReaderThread和InputDispatcherThread两个线程

主要功能：

• IMS服务中的成员变量mPtr记录Native层的NativeInputManager对象；
• IMS对象的初始化过程的重点在于native初始化，分别创建了以下对象：
  • NativeInputManager；
  • EventHub, InputManager；
  • InputReader，InputDispatcher；
  • InputReaderThread，InputDispatcherThread
• IMS启动过程的主要功能是启动以下两个线程：
  • InputReader：从EventHub取出事件并处理，再交给InputDispatcher
  • InputDispatcher：接收来自InputReader的输入事件，并派发事件到合适的窗口。

从整个启动过程，可知有system_server进程中有3个线程跟Input输入系统息息相关，分别是android.display, InputReader,InputDispatcher。

• InputDispatcher线程：属于Looper线程，会创建属于自己的Looper，循环分发消息；
• InputReader线程：通过getEvents()调用EventHub读取输入事件，循环读取消息；
• android.display线程：属于Looper线程，用于处理Java层的IMS.InputManagerHandler和JNI层的NativeInputManager中指定的MessageHandler消息;

Input事件流程：Linux Kernel -> IMS(InputReader -> InputDispatcher) -> WMS -> ViewRootImpl， 后续再进一步介绍。

四. 附录

最后在列举整个input处理流程中常见的重要对象或结构体,后续input系列文章直接使用以上结构体，可回过来查看。

4.1 InputReader.h

4.1.1 InputDevice

class InputDevice {  ...  private:      InputReaderContext* mContext;      int32_t mId;      int32_t mGeneration;      int32_t mControllerNumber;      InputDeviceIdentifier mIdentifier;      String8 mAlias;      uint32_t mClasses;      Vector<InputMapper*> mMappers;      uint32_t mSources;      bool mIsExternal;      bool mHasMic;      bool mDropUntilNextSync;      typedef int32_t (InputMapper::*GetStateFunc)(uint32_t sourceMask, int32_t code);      int32_t getState(uint32_t sourceMask, int32_t code, GetStateFunc getStateFunc);      PropertyMap mConfiguration;};

4.2 InputDispatcher.h

4.2.1 DropReason

enum DropReason {   DROP_REASON_NOT_DROPPED = 0, //不丢弃   DROP_REASON_POLICY = 1, //策略   DROP_REASON_APP_SWITCH = 2, //应用切换   DROP_REASON_DISABLED = 3, //disable   DROP_REASON_BLOCKED = 4, //阻塞   DROP_REASON_STALE = 5, //过时};enum InputTargetWaitCause {    INPUT_TARGET_WAIT_CAUSE_NONE,    INPUT_TARGET_WAIT_CAUSE_SYSTEM_NOT_READY, //系统没有准备就绪    INPUT_TARGET_WAIT_CAUSE_APPLICATION_NOT_READY, //应用没有准备就绪};EventEntry* mPendingEvent;Queue<EventEntry> mInboundQueue; //需要InputDispatcher分发的事件队列Queue<EventEntry> mRecentQueue;Queue<CommandEntry> mCommandQueue;Vector<sp<InputWindowHandle> > mWindowHandles;sp<InputWindowHandle> mFocusedWindowHandle; //聚焦窗口sp<InputApplicationHandle> mFocusedApplicationHandle; //聚焦应用String8 mLastANRState; //上一次ANR时的分发状态InputTargetWaitCause mInputTargetWaitCause;nsecs_t mInputTargetWaitStartTime;nsecs_t mInputTargetWaitTimeoutTime;bool mInputTargetWaitTimeoutExpired;//目标等待的应用sp<InputApplicationHandle> mInputTargetWaitApplicationHandle;

4.2.2 Connection

class Connection : public RefBase {    enum Status {        STATUS_NORMAL, //正常状态        STATUS_BROKEN, //发生无法恢复的错误        STATUS_ZOMBIE  //input channel被注销掉    };    Status status; //状态    sp<InputChannel> inputChannel; //永不为空    sp<InputWindowHandle> inputWindowHandle; //可能为空    bool monitor;    InputPublisher inputPublisher;    InputState inputState;    //当socket占满的同时，应用消费某些输入事件之前无法发布事件，则值为true.    bool inputPublisherBlocked;    //需要被发布到connection的事件队列    Queue<DispatchEntry> outboundQueue;    //已发布到connection，但还没有收到来自应用的“finished”响应的事件队列    Queue<DispatchEntry> waitQueue;}

4.2.3 EventEntry

struct EventEntry : Link<EventEntry> {     mutable int32_t refCount;     int32_t type; //时间类型     nsecs_t eventTime; //事件时间     uint32_t policyFlags;     InjectionState* injectionState;     bool dispatchInProgress; //初始值为false, 分发过程则设置成true };

此处type的可取值为:

• TYPE_CONFIGURATION_CHANGED
• TYPE_DEVICE_RESET
• TYPE_KEY: 按键事件
• TYPE_MOTION: 触摸时间

4.2.4 INPUT_EVENT_INJECTION

enum {    // 内部使用, 正在执行注入操作    INPUT_EVENT_INJECTION_PENDING = -1,    // 事件注入成功    INPUT_EVENT_INJECTION_SUCCEEDED = 0,    // 事件注入失败, 由于injector没有权限将聚焦的input事件注入到应用    INPUT_EVENT_INJECTION_PERMISSION_DENIED = 1,    // 事件注入失败, 由于没有可用的input target    INPUT_EVENT_INJECTION_FAILED = 2,    // 事件注入失败, 由于超时    INPUT_EVENT_INJECTION_TIMED_OUT = 3};

4.3 InputTransport.h

4.3.1 InputChannel

class InputChannel : public RefBase {    // 创建一对input channels    static status_t openInputChannelPair(const String8& name,            sp<InputChannel>& outServerChannel, sp<InputChannel>& outClientChannel);    status_t sendMessage(const InputMessage* msg); //发送消息    status_t receiveMessage(InputMessage* msg); //接收消息    //获取InputChannel的fd的拷贝    sp<InputChannel> dup() const;private:    String8 mName;    int mFd;};

sendMessage的返回值:

• OK: 代表成功;
• WOULD_BLOCK: 代表Channel已满;
• DEAD_OBJECT: 代表Channel已关闭;

receiveMessage的返回值:

• OK: 代表成功;
• WOULD_BLOCK: 代表Channel为空;
• DEAD_OBJECT: 代表Channel已关闭;

4.3.2 InputTarget

struct InputTarget {    enum {        FLAG_FOREGROUND = 1 << 0, //事件分发到前台app        FLAG_WINDOW_IS_OBSCURED = 1 << 1,        FLAG_SPLIT = 1 << 2, //MotionEvent被拆分成多窗口        FLAG_ZERO_COORDS = 1 << 3,        FLAG_DISPATCH_AS_IS = 1 << 8, //        FLAG_DISPATCH_AS_OUTSIDE = 1 << 9, //        FLAG_DISPATCH_AS_HOVER_ENTER = 1 << 10, //        FLAG_DISPATCH_AS_HOVER_EXIT = 1 << 11, //        FLAG_DISPATCH_AS_SLIPPERY_EXIT = 1 << 12, //        FLAG_DISPATCH_AS_SLIPPERY_ENTER = 1 << 13, //        FLAG_WINDOW_IS_PARTIALLY_OBSCURED = 1 << 14,        //所有分发模式的掩码        FLAG_DISPATCH_MASK = FLAG_DISPATCH_AS_IS                | FLAG_DISPATCH_AS_OUTSIDE                | FLAG_DISPATCH_AS_HOVER_ENTER                | FLAG_DISPATCH_AS_HOVER_EXIT                | FLAG_DISPATCH_AS_SLIPPERY_EXIT                | FLAG_DISPATCH_AS_SLIPPERY_ENTER,    };    sp<InputChannel> inputChannel; //目标的inputChannel    int32_t flags;    float xOffset, yOffset; //用于MotionEvent    float scaleFactor; //用于MotionEvent    BitSet32 pointerIds;};

4.3.3 InputPublisher

class InputPublisher {public:    //获取输入通道    inline sp<InputChannel> getChannel() { return mChannel; }    status_t publishKeyEvent(...); //将key event发送到input channel    status_t publishMotionEvent(...); //将motion event发送到input channel    //接收来自InputConsumer发送的完成信号    status_t receiveFinishedSignal(uint32_t* outSeq, bool* outHandled);private:    sp<InputChannel> mChannel;};

4.3.4 InputConsumer

class InputConsumer {public:    inline sp<InputChannel> getChannel() { return mChannel; }    status_t consume(...); //消费input channel的事件    //向InputPublisher发送完成信号    status_t sendFinishedSignal(uint32_t seq, bool handled);    bool hasDeferredEvent() const;    bool hasPendingBatch() const;private:    sp<InputChannel> mChannel;    InputMessage mMsg; //当前input消息    bool mMsgDeferred;    Vector<Batch> mBatches; //input批量消息    Vector<TouchState> mTouchStates;    Vector<SeqChain> mSeqChains;    status_t consumeBatch(...);    status_t consumeSamples(...);    static void initializeKeyEvent(KeyEvent* event, const InputMessage* msg);    static void initializeMotionEvent(MotionEvent* event, const InputMessage* msg);}

4.4 input.h

4.4.1 KeyEvent

class KeyEvent : public InputEvent {    ...    protected:        int32_t mAction;        int32_t mFlags;        int32_t mKeyCode;        int32_t mScanCode;        int32_t mMetaState;        int32_t mRepeatCount;        nsecs_t mDownTime; //专指按下时间        nsecs_t mEventTime; //事件发生时间(包括down/up等事件)}

4.4.2 MotionEvent

class MotionEvent : public InputEvent {    ...    protected:        int32_t mAction;        int32_t mActionButton;        int32_t mFlags;        int32_t mEdgeFlags;        int32_t mMetaState;        int32_t mButtonState;        float mXOffset;        float mYOffset;        float mXPrecision;        float mYPrecision;        nsecs_t mDownTime; //按下时间        Vector<PointerProperties> mPointerProperties;        Vector<nsecs_t> mSampleEventTimes;        Vector<PointerCoords> mSamplePointerCoords;    };}

4.5 InputListener.h

4.5.1 NotifyKeyArgs

struct NotifyKeyArgs : public NotifyArgs {    nsecs_t eventTime; //事件发生时间    int32_t deviceId;    uint32_t source;    uint32_t policyFlags;    int32_t action;    int32_t flags;    int32_t keyCode;    int32_t scanCode;    int32_t metaState;    nsecs_t downTime; //按下时间    ...};

一. InputReader起点

上一篇文章Input系统—启动篇，介绍IMS服务的启动过程会创建两个native线程，分别是InputReader,InputDispatcher. 接下来从InputReader线程的执行过程从threadLoop为起点开始分析。

1.1 threadLoop

[-> InputReader.cpp]

bool InputReaderThread::threadLoop() {    mReader->loopOnce(); //【见小节1.2】    return true;}

threadLoop返回值true代表的是会不断地循环调用loopOnce()。另外，如果当返回值为false则会 退出循环。整个过程是不断循环的地调用InputReader的loopOnce()方法，先来回顾一下InputReader对象构造方法。

1.2 loopOnce

[-> InputReader.cpp]

void InputReader::loopOnce() {    ...    {        AutoMutex _l(mLock);        uint32_t changes = mConfigurationChangesToRefresh;        if (changes) {            timeoutMillis = 0;            ...        } else if (mNextTimeout != LLONG_MAX) {            nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);            timeoutMillis = toMillisecondTimeoutDelay(now, mNextTimeout);        }    }    //从EventHub读取事件，其中EVENT_BUFFER_SIZE = 256【见小节2.1】    size_t count = mEventHub->getEvents(timeoutMillis, mEventBuffer, EVENT_BUFFER_SIZE);    { // acquire lock        AutoMutex _l(mLock);         mReaderIsAliveCondition.broadcast();        if (count) { //处理事件【见小节3.1】            processEventsLocked(mEventBuffer, count);        }        if (oldGeneration != mGeneration) {            inputDevicesChanged = true;            getInputDevicesLocked(inputDevices);        }        ...    } // release lock    if (inputDevicesChanged) { //输入设备发生改变        mPolicy->notifyInputDevicesChanged(inputDevices);    }    //发送事件到nputDispatcher【见小节4.1】    mQueuedListener->flush();}

二. EventHub

2.1 getEvents

[-> EventHub.cpp]

size_t EventHub::getEvents(int timeoutMillis, RawEvent* buffer, size_t bufferSize) {    AutoMutex _l(mLock); //加锁    struct input_event readBuffer[bufferSize];    RawEvent* event = buffer; //原始事件    size_t capacity = bufferSize; //容量大小为256    bool awoken = false;    for (;;) {        nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);        ...        if (mNeedToScanDevices) {            mNeedToScanDevices = false;            scanDevicesLocked(); //扫描设备【见小节2.2】            mNeedToSendFinishedDeviceScan = true;        }        while (mOpeningDevices != NULL) {            Device* device = mOpeningDevices;            mOpeningDevices = device->next;            event->when = now;            event->deviceId = device->id == mBuiltInKeyboardId ? 0 : device->id;            event->type = DEVICE_ADDED; //添加设备的事件            event += 1;            mNeedToSendFinishedDeviceScan = true;            if (--capacity == 0) {                break;            }        }        ...        bool deviceChanged = false;        while (mPendingEventIndex < mPendingEventCount) {            //从mPendingEventItems读取事件项            const struct epoll_event& eventItem = mPendingEventItems[mPendingEventIndex++];            ...            //获取设备ID所对应的device            ssize_t deviceIndex = mDevices.indexOfKey(eventItem.data.u32);            Device* device = mDevices.valueAt(deviceIndex);            if (eventItem.events & EPOLLIN) {                //从设备不断读取事件，放入到readBuffer                int32_t readSize = read(device->fd, readBuffer,                        sizeof(struct input_event) * capacity);                if (readSize == 0 || (readSize < 0 && errno == ENODEV)) {                    deviceChanged = true;                    closeDeviceLocked(device);//设备已被移除则执行关闭操作                } else if (readSize < 0) {                    ...                } else if ((readSize % sizeof(struct input_event)) != 0) {                    ...                } else {                    int32_t deviceId = device->id == mBuiltInKeyboardId ? 0 : device->id;                    size_t count = size_t(readSize) / sizeof(struct input_event);                    for (size_t i = 0; i < count; i++) {                        //获取readBuffer的数据                        struct input_event& iev = readBuffer[i];                        //将input_event信息, 封装成RawEvent                        event->when = nsecs_t(iev.time.tv_sec) * 1000000000LL                                + nsecs_t(iev.time.tv_usec) * 1000LL;                        event->deviceId = deviceId;                        event->type = iev.type;                        event->code = iev.code;                        event->value = iev.value;                        event += 1;                        capacity -= 1;                    }                    if (capacity == 0) {                        mPendingEventIndex -= 1;                        break;                    }                }            }            ...        }        ...        mLock.unlock(); //poll之前先释放锁        //等待input事件的到来        int pollResult = epoll_wait(mEpollFd, mPendingEventItems, EPOLL_MAX_EVENTS, timeoutMillis);        ...        mLock.lock(); //poll之后再次请求锁        if (pollResult < 0) { //出现错误            mPendingEventCount = 0;            if (errno != EINTR) {                usleep(100000); //系统发生错误则休眠1s            }        } else {            mPendingEventCount = size_t(pollResult);        }    }    return event - buffer; //返回所读取的事件个数}

EventHub采用INotify + epoll机制实现监听目录/dev/input下的设备节点，经过EventHub将input_event结构体 + deviceId 转换成RawEvent结构体，如下：

2.1.1 RawEvent

[-> InputEventReader.h]

struct input_event { struct timeval time; //事件发生的时间点 __u16 type; __u16 code; __s32 value;};struct RawEvent {    nsecs_t when; //事件发生的时间店    int32_t deviceId; //产生事件的设备Id    int32_t type; // 事件类型    int32_t code;    int32_t value;};

此处事件类型:

• DEVICE_ADDED(添加)
• DEVICE_REMOVED(删除)
• FINISHED_DEVICE_SCAN(扫描完成)
• type<FIRST_SYNTHETIC_EVENT(其他事件)

getEvents()已完成转换事件转换工作, 接下来,顺便看看设备扫描过程.

2.2 设备扫描

2.2.1 scanDevicesLocked

void EventHub::scanDevicesLocked() {    //此处DEVICE_PATH="/dev/input"【见小节2.3】    status_t res = scanDirLocked(DEVICE_PATH);    ...}

2.2.2 scanDirLocked

status_t EventHub::scanDirLocked(const char *dirname){    char devname[PATH_MAX];    char *filename;    DIR *dir;    struct dirent *de;    dir = opendir(dirname);    strcpy(devname, dirname);    filename = devname + strlen(devname);    *filename++ = '/';    //读取/dev/input/目录下所有的设备节点    while((de = readdir(dir))) {        if(de->d_name[0] == '.' &&           (de->d_name[1] == '\0' ||            (de->d_name[1] == '.' && de->d_name[2] == '\0')))            continue;        strcpy(filename, de->d_name);        //打开相应的设备节点【2.2.3】        openDeviceLocked(devname);    }    closedir(dir);    return 0;}

2.2.3 openDeviceLocked

status_t EventHub::openDeviceLocked(const char *devicePath) {    char buffer[80];    //打开设备文件    int fd = open(devicePath, O_RDWR | O_CLOEXEC);    InputDeviceIdentifier identifier;    //获取设备名    if(ioctl(fd, EVIOCGNAME(sizeof(buffer) - 1), &buffer) < 1){    } else {        buffer[sizeof(buffer) - 1] = '\0';        identifier.name.setTo(buffer);    }    identifier.bus = inputId.bustype;    identifier.product = inputId.product;    identifier.vendor = inputId.vendor;    identifier.version = inputId.version;    //获取设备物理地址    if(ioctl(fd, EVIOCGPHYS(sizeof(buffer) - 1), &buffer) < 1) {    } else {        buffer[sizeof(buffer) - 1] = '\0';        identifier.location.setTo(buffer);    }    //获取设备唯一ID    if(ioctl(fd, EVIOCGUNIQ(sizeof(buffer) - 1), &buffer) < 1) {    } else {        buffer[sizeof(buffer) - 1] = '\0';        identifier.uniqueId.setTo(buffer);    }    //将identifier信息填充到fd    assignDescriptorLocked(identifier);    //设置fd为非阻塞方式    fcntl(fd, F_SETFL, O_NONBLOCK);    //获取设备ID，分配设备对象内存    int32_t deviceId = mNextDeviceId++;    Device* device = new Device(fd, deviceId, String8(devicePath), identifier);    ...    //注册epoll    struct epoll_event eventItem;    memset(&eventItem, 0, sizeof(eventItem));    eventItem.events = EPOLLIN;    if (mUsingEpollWakeup) {        eventItem.events |= EPOLLWAKEUP;    }    eventItem.data.u32 = deviceId;    if (epoll_ctl(mEpollFd, EPOLL_CTL_ADD, fd, &eventItem)) {        delete device; //添加失败则删除该设备        return -1;    }    ...    //【见小节2.2.4】    addDeviceLocked(device);}

2.2.4 addDeviceLocked

void EventHub::addDeviceLocked(Device* device) {    mDevices.add(device->id, device); //添加到mDevices队列    device->next = mOpeningDevices;    mOpeningDevices = device;}

介绍了EventHub从设备节点获取事件的流程，当收到事件后接下里便开始处理事件。

三. InputReader

3.1 processEventsLocked

[-> InputReader.cpp]

void InputReader::processEventsLocked(const RawEvent* rawEvents, size_t count) {    for (const RawEvent* rawEvent = rawEvents; count;) {        int32_t type = rawEvent->type;        size_t batchSize = 1;        if (type < EventHubInterface::FIRST_SYNTHETIC_EVENT) {            int32_t deviceId = rawEvent->deviceId;            while (batchSize < count) {                if (rawEvent[batchSize].type >= EventHubInterface::FIRST_SYNTHETIC_EVENT                        || rawEvent[batchSize].deviceId != deviceId) {                    break;                }                batchSize += 1; //同一设备的事件打包处理            }            //数据事件的处理【见小节3.3】            processEventsForDeviceLocked(deviceId, rawEvent, batchSize);        } else {            switch (rawEvent->type) {            case EventHubInterface::DEVICE_ADDED:                //设备添加【见小节3.2】                addDeviceLocked(rawEvent->when, rawEvent->deviceId);                break;            case EventHubInterface::DEVICE_REMOVED:                //设备移除                removeDeviceLocked(rawEvent->when, rawEvent->deviceId);                break;            case EventHubInterface::FINISHED_DEVICE_SCAN:                //设备扫描完成                handleConfigurationChangedLocked(rawEvent->when);                break;            default:                ALOG_ASSERT(false);//不会发生                break;            }        }        count -= batchSize;        rawEvent += batchSize;    }}

事件处理总共有下几类类型：

• DEVICE_ADDED(设备增加), [见小节3.2]
• DEVICE_REMOVED(设备移除)
• FINISHED_DEVICE_SCAN(设备扫描完成)
• 数据事件[见小节3.4]

先来说说DEVICE_ADDED设备增加的过程。

3.2 设备增加

3.2.1 addDeviceLocked

void InputReader::addDeviceLocked(nsecs_t when, int32_t deviceId) {    ssize_t deviceIndex = mDevices.indexOfKey(deviceId);    if (deviceIndex >= 0) {        return; //已添加的相同设备则不再添加    }    InputDeviceIdentifier identifier = mEventHub->getDeviceIdentifier(deviceId);    uint32_t classes = mEventHub->getDeviceClasses(deviceId);    int32_t controllerNumber = mEventHub->getDeviceControllerNumber(deviceId);    //【见小节3.2.2】    InputDevice* device = createDeviceLocked(deviceId, controllerNumber, identifier, classes);    device->configure(when, &mConfig, 0);    device->reset(when);    mDevices.add(deviceId, device); //添加设备到mDevices    ...}

3.2.2 createDeviceLocked

InputDevice* InputReader::createDeviceLocked(int32_t deviceId, int32_t controllerNumber,        const InputDeviceIdentifier& identifier, uint32_t classes) {    //创建InputDevice对象    InputDevice* device = new InputDevice(&mContext, deviceId, bumpGenerationLocked(),            controllerNumber, identifier, classes);    ...    //获取键盘源类型    uint32_t keyboardSource = 0;    int32_t keyboardType = AINPUT_KEYBOARD_TYPE_NON_ALPHABETIC;    if (classes & INPUT_DEVICE_CLASS_KEYBOARD) {        keyboardSource |= AINPUT_SOURCE_KEYBOARD;    }    if (classes & INPUT_DEVICE_CLASS_ALPHAKEY) {        keyboardType = AINPUT_KEYBOARD_TYPE_ALPHABETIC;    }    if (classes & INPUT_DEVICE_CLASS_DPAD) {        keyboardSource |= AINPUT_SOURCE_DPAD;    }    if (classes & INPUT_DEVICE_CLASS_GAMEPAD) {        keyboardSource |= AINPUT_SOURCE_GAMEPAD;    }    //添加键盘类设备InputMapper    if (keyboardSource != 0) {        device->addMapper(new KeyboardInputMapper(device, keyboardSource, keyboardType));    }    //添加鼠标类设备InputMapper    if (classes & INPUT_DEVICE_CLASS_CURSOR) {        device->addMapper(new CursorInputMapper(device));    }    //添加触摸屏设备InputMapper    if (classes & INPUT_DEVICE_CLASS_TOUCH_MT) {        device->addMapper(new MultiTouchInputMapper(device));    } else if (classes & INPUT_DEVICE_CLASS_TOUCH) {        device->addMapper(new SingleTouchInputMapper(device));    }    ...    return device;}

该方法主要功能：

• 创建InputDevice对象，将InputReader的mContext赋给InputDevice对象所对应的变量
• 根据设备类型来创建并添加相对应的InputMapper，同时设置mContext.

input设备类型有很多种，以上代码只列举部分常见的设备以及相应的InputMapper：

• 键盘类设备：KeyboardInputMapper
• 触摸屏设备：MultiTouchInputMapper或SingleTouchInputMapper
• 鼠标类设备：CursorInputMapper

介绍完设备增加过程，继续回到[小节3.1]除了设备的增删，更常见事件便是数据事件，那么接下来介绍数据事件的 处理过程。

3.3 事件处理

3.3.1 processEventsForDeviceLocked

void InputReader::processEventsForDeviceLocked(int32_t deviceId,        const RawEvent* rawEvents, size_t count) {    ssize_t deviceIndex = mDevices.indexOfKey(deviceId);    ...    InputDevice* device = mDevices.valueAt(deviceIndex);    if (device->isIgnored()) {        return; //可忽略则直接返回    }    //【见小节3.3.2】    device->process(rawEvents, count);}

3.3.2 InputDevice.process

void InputDevice::process(const RawEvent* rawEvents, size_t count) {    size_t numMappers = mMappers.size();    for (const RawEvent* rawEvent = rawEvents; count--; rawEvent++) {        if (mDropUntilNextSync) {            if (rawEvent->type == EV_SYN && rawEvent->code == SYN_REPORT) {                mDropUntilNextSync = false;            }        } else if (rawEvent->type == EV_SYN && rawEvent->code == SYN_DROPPED) {            mDropUntilNextSync = true;            reset(rawEvent->when);        } else {            for (size_t i = 0; i < numMappers; i++) {                InputMapper* mapper = mMappers[i];                //调用具体mapper来处理【见小节3.4】                mapper->process(rawEvent);            }        }    }}

小节[3.2]createDeviceLocked创建设备并添加InputMapper，提到会有多种InputMapper。 这里以KeyboardInputMapper(按键事件)为例来展开说明

3.4 按键事件处理

3.4.1 KeyboardInputMapper.process

[-> InputReader.cpp ::KeyboardInputMapper]

void KeyboardInputMapper::process(const RawEvent* rawEvent) {    switch (rawEvent->type) {    case EV_KEY: {        int32_t scanCode = rawEvent->code;        int32_t usageCode = mCurrentHidUsage;        mCurrentHidUsage = 0;        if (isKeyboardOrGamepadKey(scanCode)) {            int32_t keyCode;            //获取所对应的KeyCode【见小节3.4.2】            if (getEventHub()->mapKey(getDeviceId(), scanCode, usageCode, &keyCode, &flags)) {                keyCode = AKEYCODE_UNKNOWN;                flags = 0;            }            //【见小节3.4.4】            processKey(rawEvent->when, rawEvent->value != 0, keyCode, scanCode, flags);        }        break;    }    case EV_MSC: ...    case EV_SYN: ...    }}

3.4.2 EventHub::mapKey

[-> EventHub.cpp]

status_t EventHub::mapKey(int32_t deviceId,        int32_t scanCode, int32_t usageCode, int32_t metaState,        int32_t* outKeycode, int32_t* outMetaState, uint32_t* outFlags) const {    AutoMutex _l(mLock);    Device* device = getDeviceLocked(deviceId); //获取设备对象    status_t status = NAME_NOT_FOUND;    if (device) {        sp<KeyCharacterMap> kcm = device->getKeyCharacterMap();        if (kcm != NULL) {            //根据scanCode找到keyCode【见小节3.4.3】            if (!kcm->mapKey(scanCode, usageCode, outKeycode)) {                *outFlags = 0;                status = NO_ERROR;            }        }    }    ...    return status;}

将事件的扫描码(scanCode)转换成键盘码(Keycode)

3.4.3 KeyCharacterMap::mapKey

[-> KeyCharacterMap.cpp]

status_t KeyCharacterMap::mapKey(int32_t scanCode, int32_t usageCode, int32_t* outKeyCode) const {    ...    if (scanCode) {        ssize_t index = mKeysByScanCode.indexOfKey(scanCode);        if (index >= 0) {            //根据scanCode找到keyCode            *outKeyCode = mKeysByScanCode.valueAt(index);            return OK;        }    }    *outKeyCode = AKEYCODE_UNKNOWN;    return NAME_NOT_FOUND;}

再回到[3.4.1],接下来进入如下过程:

3.4.4 InputMapper.processKey

[-> InputReader.cpp]

void KeyboardInputMapper::processKey(nsecs_t when, bool down, int32_t keyCode,        int32_t scanCode, uint32_t policyFlags) {    if (down) {        if (mParameters.orientationAware && mParameters.hasAssociatedDisplay) {            keyCode = rotateKeyCode(keyCode, mOrientation);        }        ssize_t keyDownIndex = findKeyDown(scanCode);        if (keyDownIndex >= 0) {            //mKeyDowns记录着所有按下的键            keyCode = mKeyDowns.itemAt(keyDownIndex).keyCode;        } else {            ...            mKeyDowns.push(); //压入栈顶            KeyDown& keyDown = mKeyDowns.editTop();            keyDown.keyCode = keyCode;            keyDown.scanCode = scanCode;        }        mDownTime = when; //记录按下时间点    } else {        ssize_t keyDownIndex = findKeyDown(scanCode);        if (keyDownIndex >= 0) {            //键抬起操作，则移除按下事件            keyCode = mKeyDowns.itemAt(keyDownIndex).keyCode;            mKeyDowns.removeAt(size_t(keyDownIndex));        } else {            return;  //键盘没有按下操作，则直接忽略抬起操作        }    }    nsecs_t downTime = mDownTime;    ...    //创建NotifyKeyArgs对象, when记录eventTime, downTime记录按下时间；    NotifyKeyArgs args(when, getDeviceId(), mSource, policyFlags,            down ? AKEY_EVENT_ACTION_DOWN : AKEY_EVENT_ACTION_UP,            AKEY_EVENT_FLAG_FROM_SYSTEM, keyCode, scanCode, newMetaState, downTime);    //通知key事件【见小节3.4.5】    getListener()->notifyKey(&args);}

参数说明：

• mKeyDowns记录着所有按下的键;
• mDownTime记录按下时间点;
• 此处KeyboardInputMapper的mContext指向InputReader，getListener()获取的便是mQueuedListener。 接下来调用该对象的notifyKey.

3.4.5 QueuedInputListener.notifyKey

[-> InputListener.cpp]

void QueuedInputListener::notifyKey(const NotifyKeyArgs* args) {    mArgsQueue.push(new NotifyKeyArgs(*args));}

mArgsQueue的数据类型为Vector<NotifyArgs*>，将该key事件压人该栈顶。 到此,整个事件加工完成, 再然后就是将事件发送给InputDispatcher线程.

四. QueuedListener

4.1 QueuedInputListener.flush

[-> InputListener.cpp]

void QueuedInputListener::flush() {    size_t count = mArgsQueue.size();    for (size_t i = 0; i < count; i++) {        NotifyArgs* args = mArgsQueue[i];        //【见小节4.2】        args->notify(mInnerListener);        delete args;    }    mArgsQueue.clear();}

从InputManager对象初始化的过程可知，mInnerListener便是InputDispatcher对象。

4.2 NotifyKeyArgs.notify

[-> InputListener.cpp]

void NotifyKeyArgs::notify(const sp<InputListenerInterface>& listener) const {    listener->notifyKey(this); // this是指NotifyKeyArgs【见小节4.3】}

4.3 InputDispatcher.notifyKey

[-> InputDispatcher.cpp]

void InputDispatcher::notifyKey(const NotifyKeyArgs* args) {    if (!validateKeyEvent(args->action)) {        return;    }    ...    int32_t keyCode = args->keyCode;    if (keyCode == AKEYCODE_HOME) {        if (args->action == AKEY_EVENT_ACTION_DOWN) {            property_set("sys.domekey.down", "1");        } else if (args->action == AKEY_EVENT_ACTION_UP) {            property_set("sys.domekey.down", "0");        }    }    if (metaState & AMETA_META_ON && args->action == AKEY_EVENT_ACTION_DOWN) {        ...    } else if (args->action == AKEY_EVENT_ACTION_UP) {        ...    }    KeyEvent event; //初始化KeyEvent对象    event.initialize(args->deviceId, args->source, args->action,            flags, keyCode, args->scanCode, metaState, 0,            args->downTime, args->eventTime);    //mPolicy是指NativeInputManager对象。【小节4.3.1】    mPolicy->interceptKeyBeforeQueueing(&event, /*byref*/ policyFlags);    bool needWake;    {        mLock.lock();        if (shouldSendKeyToInputFilterLocked(args)) {            mLock.unlock();            policyFlags |= POLICY_FLAG_FILTERED;            //当inputEventObj不为空, 则事件被filter所拦截【见小节4.3.2】            if (!mPolicy->filterInputEvent(&event, policyFlags)) {                return;            }            mLock.lock();        }        int32_t repeatCount = 0;        //创建KeyEntry对象        KeyEntry* newEntry = new KeyEntry(args->eventTime,                args->deviceId, args->source, policyFlags,                args->action, flags, keyCode, args->scanCode,                metaState, repeatCount, args->downTime);        //将KeyEntry放入队列【见小节4.3.3】        needWake = enqueueInboundEventLocked(newEntry);        mLock.unlock();    }    if (needWake) {        //唤醒InputDispatcher线程【见小节4.3.5】        mLooper->wake();    }}

该方法的主要功能：

1. 调用NativeInputManager.interceptKeyBeforeQueueing，加入队列前执行拦截动作，但并不改变流程，调用链：
   • IMS.interceptKeyBeforeQueueing
   • InputMonitor.interceptKeyBeforeQueueing (继承IMS.WindowManagerCallbacks)
   • PhoneWindowManager.interceptKeyBeforeQueueing (继承WindowManagerPolicy)
2. 当mInputFilterEnabled=true(该值默认为false,可通过setInputFilterEnabled设置),则调用NativeInputManager.filterInputEvent过滤输入事件；
   • 当返回值为false则过滤该事件，不再往下分发；
3. 生成KeyEvent，并调用enqueueInboundEventLocked，将该事件加入到InputDispatcherd的成员变量mInboundQueue。

4.3.1 interceptKeyBeforeQueueing

void NativeInputManager::interceptKeyBeforeQueueing(const KeyEvent* keyEvent,        uint32_t& policyFlags) {    ...    if ((policyFlags & POLICY_FLAG_TRUSTED)) {        nsecs_t when = keyEvent->getEventTime(); //时间        JNIEnv* env = jniEnv();        jobject keyEventObj = android_view_KeyEvent_fromNative(env, keyEvent);        if (keyEventObj) {            // 调用Java层的IMS.interceptKeyBeforeQueueing            wmActions = env->CallIntMethod(mServiceObj,                    gServiceClassInfo.interceptKeyBeforeQueueing,                    keyEventObj, policyFlags);            ...        } else {            ...        }        handleInterceptActions(wmActions, when, /*byref*/ policyFlags);    } else {        ...    }}

该方法会调用Java层的InputManagerService的interceptKeyBeforeQueueing()方法。

4.3.2 filterInputEvent

bool NativeInputManager::filterInputEvent(const InputEvent* inputEvent, uint32_t policyFlags) {    jobject inputEventObj;    JNIEnv* env = jniEnv();    switch (inputEvent->getType()) {    case AINPUT_EVENT_TYPE_KEY:        inputEventObj = android_view_KeyEvent_fromNative(env,                static_cast<const KeyEvent*>(inputEvent));        break;    case AINPUT_EVENT_TYPE_MOTION:        inputEventObj = android_view_MotionEvent_obtainAsCopy(env,                static_cast<const MotionEvent*>(inputEvent));        break;    default:        return true; // 走事件正常的分发流程    }    if (!inputEventObj) {        return true; // 当inputEventObj为空, 则走事件正常的分发流程    }    //当inputEventObj不为空,则调用Java层的IMS.filterInputEvent()    jboolean pass = env->CallBooleanMethod(mServiceObj, gServiceClassInfo.filterInputEvent,            inputEventObj, policyFlags);    if (checkAndClearExceptionFromCallback(env, "filterInputEvent")) {        pass = true; //出现Exception，则走事件正常的分发流程    }    env->DeleteLocalRef(inputEventObj);    return pass;}

当inputEventObj不为空,则调用Java层的IMS.filterInputEvent(). 经过层层调用后, 最终会再调用InputDispatcher.injectInputEvent(),该基本等效于该方法的后半段:

• enqueueInboundEventLocked
• wakeup

4.3.3 enqueueInboundEventLocked

bool InputDispatcher::enqueueInboundEventLocked(EventEntry* entry) {    bool needWake = mInboundQueue.isEmpty();    mInboundQueue.enqueueAtTail(entry); //将该事件放入mInboundQueue队列尾部    switch (entry->type) {    case EventEntry::TYPE_KEY: {        KeyEntry* keyEntry = static_cast<KeyEntry*>(entry);        if (isAppSwitchKeyEventLocked(keyEntry)) {            if (keyEntry->action == AKEY_EVENT_ACTION_DOWN) {                mAppSwitchSawKeyDown = true; //按下事件            } else if (keyEntry->action == AKEY_EVENT_ACTION_UP) {                if (mAppSwitchSawKeyDown) {                    //其中APP_SWITCH_TIMEOUT=500ms                    mAppSwitchDueTime = keyEntry->eventTime + APP_SWITCH_TIMEOUT;                    mAppSwitchSawKeyDown = false;                    needWake = true;                }            }        }        break;    }    case EventEntry::TYPE_MOTION: {        //当前App无响应且用户希望切换到其他应用窗口，则drop该窗口事件，并处理其他窗口事件        MotionEntry* motionEntry = static_cast<MotionEntry*>(entry);        if (motionEntry->action == AMOTION_EVENT_ACTION_DOWN                && (motionEntry->source & AINPUT_SOURCE_CLASS_POINTER)                && mInputTargetWaitCause == INPUT_TARGET_WAIT_CAUSE_APPLICATION_NOT_READY                && mInputTargetWaitApplicationHandle != NULL) {            int32_t displayId = motionEntry->displayId;            int32_t x = int32_t(motionEntry->pointerCoords[0].                    getAxisValue(AMOTION_EVENT_AXIS_X));            int32_t y = int32_t(motionEntry->pointerCoords[0].                    getAxisValue(AMOTION_EVENT_AXIS_Y));            //查询可触摸的窗口【见小节4.3.4】            sp<InputWindowHandle> touchedWindowHandle = findTouchedWindowAtLocked(displayId, x, y);            if (touchedWindowHandle != NULL                    && touchedWindowHandle->inputApplicationHandle                            != mInputTargetWaitApplicationHandle) {                mNextUnblockedEvent = motionEntry;                needWake = true;            }        }        break;    }    }    return needWake;}

AppSwitchKeyEvent是指keyCode等于以下值：

• AKEYCODE_HOME
• AKEYCODE_ENDCALL
• AKEYCODE_APP_SWITCH

4.3.4 findTouchedWindowAtLocked

[-> InputDispatcher.cpp]

sp<InputWindowHandle> InputDispatcher::findTouchedWindowAtLocked(int32_t displayId,        int32_t x, int32_t y) {    //从前台到后台来遍历查询可触摸的窗口    size_t numWindows = mWindowHandles.size();    for (size_t i = 0; i < numWindows; i++) {        sp<InputWindowHandle> windowHandle = mWindowHandles.itemAt(i);        const InputWindowInfo* windowInfo = windowHandle->getInfo();        if (windowInfo->displayId == displayId) {            int32_t flags = windowInfo->layoutParamsFlags;            if (windowInfo->visible) {                if (!(flags & InputWindowInfo::FLAG_NOT_TOUCHABLE)) {                    bool isTouchModal = (flags & (InputWindowInfo::FLAG_NOT_FOCUSABLE                            | InputWindowInfo::FLAG_NOT_TOUCH_MODAL)) == 0;                    if (isTouchModal || windowInfo->touchableRegionContainsPoint(x, y)) {                        return windowHandle; //找到目标窗口                    }                }            }        }    }    return NULL;}

此处mWindowHandles的赋值过程是由Java层的InputMonitor.setInputWindows(),经过JNI调用后进入InputDispatcher::setInputWindows()方法完成. 进一步说, 就是WMS执行addWindow()过程或许UI改变等场景,都会触发该方法的修改.

4.3.5 Looper.wake

[-> system/core/libutils/Looper.cpp]

void Looper::wake() {    uint64_t inc = 1;    ssize_t nWrite = TEMP_FAILURE_RETRY(write(mWakeEventFd, &inc, sizeof(uint64_t)));    if (nWrite != sizeof(uint64_t)) {        if (errno != EAGAIN) {            ALOGW("Could not write wake signal, errno=%d", errno);        }    }}

[小节4.3]的过程会调用enqueueInboundEventLocked()方法来决定是否需要将数字1写入句柄mWakeEventFd来唤醒InputDispatcher线程. 满足唤醒的条件:

1. 执行enqueueInboundEventLocked方法前,mInboundQueue队列为空,执行完必然不再为空,则需要唤醒分发线程;
2. 当事件类型为key事件,且发生一对按下和抬起操作,则需要唤醒;
3. 当事件类型为motion事件,且当前可触摸的窗口属于另一个应用,则需要唤醒.

五. 总结

5.1 核心工作

InputReader整个过程涉及多次事件封装转换，其主要工作核心是以下三大步骤:

• getEvents：通过EventHub(监听目录/dev/input)读取事件放入mEventBuffer,而mEventBuffer是一个大小为256的数组, 再将事件input_event转换为RawEvent; [见小节2.1]
• processEventsLocked: 对事件进行加工, 转换RawEvent -> NotifyKeyArgs(NotifyArgs) [见小节3.1]
• QueuedListener->flush：将事件发送到InputDispatcher线程, 转换NotifyKeyArgs -> KeyEntry(EventEntry) [见小节4.1]

InputReader线程不断循环地执行InputReader.loopOnce(), 每次处理完生成的是EventEntry(比如KeyEntry, MotionEntry), 接下来的工作就交给InputDispatcher线程。

5.2 流程图

点击查看大图:

InputReader的核心工作就是从EventHub获取数据后生成EventEntry事件，加入到InputDispatcher的mInboundQueue队列，再唤醒InputDispatcher线程。

说明:

• IMS.filterInputEvent可以过滤无需上报的事件，当该方法返回值为false则代表是需要被过滤掉的事件，无机会交给InputDispatcher来分发。
• 节点/dev/input的event事件所对应的输入设备信息位于/proc/bus/input/devices，也可以通过getevent来获取事件. 不同的input事件所对应的物理input节点，比如常见的情形：
  • 屏幕触摸和(MENU,HOME,BACK)3按键：对应同一个input设备节点；
  • POWER和音量(下)键：对应同一个input设备节点；
  • 音量(上)键：对应同一个input设备节点；

一. InputDispatcher起点

上篇文章输入系统之InputReader线程，介绍InputReader利用EventHub获取数据后生成EventEntry事件，加入到InputDispatcher的mInboundQueue队列，再唤醒InputDispatcher线程。本文将介绍InputDispatcher，同样从threadLoop为起点开始分析。

1.1 threadLoop

先来回顾一下InputDispatcher对象的初始化过程:

InputDispatcher::InputDispatcher(const sp<InputDispatcherPolicyInterface>& policy) :    mPolicy(policy),    mPendingEvent(NULL), mLastDropReason(DROP_REASON_NOT_DROPPED),    mAppSwitchSawKeyDown(false), mAppSwitchDueTime(LONG_LONG_MAX),    mNextUnblockedEvent(NULL),    mDispatchEnabled(false), mDispatchFrozen(false), mInputFilterEnabled(false),    mInputTargetWaitCause(INPUT_TARGET_WAIT_CAUSE_NONE) {    //创建Looper对象    mLooper = new Looper(false);    mKeyRepeatState.lastKeyEntry = NULL;    //获取分发超时参数    policy->getDispatcherConfiguration(&mConfig);}

该方法主要工作：

• 创建属于自己线程的Looper对象；
• 超时参数来自于IMS，参数默认值keyRepeatTimeout = 500，keyRepeatDelay = 50。

[-> InputDispatcher.cpp]

bool InputDispatcherThread::threadLoop() {    mDispatcher->dispatchOnce(); //【见小节1.2】    return true;}

整个过程不断循环地调用InputDispatcher的dispatchOnce()来分发事件

1.2 dispatchOnce

[-> InputDispatcher.cpp]

void InputDispatcher::dispatchOnce() {    nsecs_t nextWakeupTime = LONG_LONG_MAX;    {        AutoMutex _l(mLock);        //唤醒等待线程，monitor()用于监控dispatcher是否发生死锁        mDispatcherIsAliveCondition.broadcast();        if (!haveCommandsLocked()) {            //当mCommandQueue不为空时处理【见小节2.1】            dispatchOnceInnerLocked(&nextWakeupTime);        }        //【见小节3.1】        if (runCommandsLockedInterruptible()) {            nextWakeupTime = LONG_LONG_MIN;        }    }    nsecs_t currentTime = now();    int timeoutMillis = toMillisecondTimeoutDelay(currentTime, nextWakeupTime);    mLooper->pollOnce(timeoutMillis); //进入epoll_wait}

线程执行Looper->pollOnce，进入epoll_wait等待状态，当发生以下任一情况则退出等待状态：

1. callback：通过回调方法来唤醒；
2. timeout：到达nextWakeupTime时间，超时唤醒；
3. wake: 主动调用Looper的wake()方法；

二. InputDispatcher

2.1 dispatchOnceInnerLocked

void InputDispatcher::dispatchOnceInnerLocked(nsecs_t* nextWakeupTime) {    nsecs_t currentTime = now(); //当前时间    if (!mDispatchEnabled) { //默认值为false        resetKeyRepeatLocked(); //重置操作    }    if (mDispatchFrozen) { //默认值为false        return; //当分发被冻结，则不再处理超时和分发事件的工作，直接返回    }    //优化app切换延迟，当切换超时，则抢占分发，丢弃其他所有即将要处理的事件。    bool isAppSwitchDue = mAppSwitchDueTime <= currentTime;    ...    if (!mPendingEvent) {        if (mInboundQueue.isEmpty()) {            if (!mPendingEvent) {                return; //没有事件需要处理，则直接返回            }        } else {            //从mInboundQueue取出头部的事件            mPendingEvent = mInboundQueue.dequeueAtHead();        }        ...        resetANRTimeoutsLocked(); //重置ANR信息[见小节2.1.1]    }    bool done = false;    DropReason dropReason = DROP_REASON_NOT_DROPPED;    if (!(mPendingEvent->policyFlags & POLICY_FLAG_PASS_TO_USER)) {        dropReason = DROP_REASON_POLICY;    } else if (!mDispatchEnabled) {        dropReason = DROP_REASON_DISABLED;    }    ...    switch (mPendingEvent->type) {      case EventEntry::TYPE_KEY: {          KeyEntry* typedEntry = static_cast<KeyEntry*>(mPendingEvent);          if (isAppSwitchDue) {              if (isAppSwitchKeyEventLocked(typedEntry)) {                  resetPendingAppSwitchLocked(true);                  isAppSwitchDue = false;              } else if (dropReason == DROP_REASON_NOT_DROPPED) {                  dropReason = DROP_REASON_APP_SWITCH;              }          }          if (dropReason == DROP_REASON_NOT_DROPPED                  && isStaleEventLocked(currentTime, typedEntry)) {              dropReason = DROP_REASON_STALE;          }          if (dropReason == DROP_REASON_NOT_DROPPED && mNextUnblockedEvent) {              dropReason = DROP_REASON_BLOCKED;          }          // 分发按键事件[见小节2.2]          done = dispatchKeyLocked(currentTime, typedEntry, &dropReason, nextWakeupTime);          break;      }      ...    }    ...    //分发操作完成，则进入该分支    if (done) {        if (dropReason != DROP_REASON_NOT_DROPPED) {            //[见小节2.1.2]            dropInboundEventLocked(mPendingEvent, dropReason);        }        mLastDropReason = dropReason;        releasePendingEventLocked(); //释放pending事件见小节2.10]        *nextWakeupTime = LONG_LONG_MIN; //强制立刻执行轮询    }}

在enqueueInboundEventLocked()的过程中已设置mAppSwitchDueTime等于eventTime加上500ms:

mAppSwitchDueTime = keyEntry->eventTime + APP_SWITCH_TIMEOUT;

该方法主要功能:

1. mDispatchFrozen用于决定是否冻结事件分发工作不再往下执行;
2. 当事件分发的时间点距离该事件加入mInboundQueue的时间超过500ms,则认为app切换过期,即isAppSwitchDue=true;
3. mInboundQueue不为空,则取出头部的事件,放入mPendingEvent变量;并重置ANR时间;
4. 根据EventEntry的type类型分别处理，比如按键调用dispatchKeyLocked分发事件;再根据分发结果来决定是否进入done;
5. 执行完成(done)的处理:
   • 根据dropReason(默认NOT_DROPPED不处理)来决定是否丢失事件; dropInboundEventLocked
   • 释放当前正在处理的事件(即mPendingEvent)； releasePendingEventLocked

关于dispatchKeyLocked分发事件,

1. 不会执行done过情况:
   • 当前Event时间小于唤醒时间;
   • 让policy有机会执行拦截操作;
   • 调用findFocusedWindowTargetsLocked方法的返回结果是INPUT_EVENT_INJECTION_PENDING, 即targets没有处于Ready状态;
2. 会执行done的情况:
   • 该事件需要丢弃, 即dropReason != DROP_REASON_NOT_DROPPED;
   • findFocusedWindowTargetsLocked的返回结果不是INPUT_EVENT_INJECTION_PENDING(没有正在处理的事件);

接下来以按键为例来展开说明, 则进入[小节2.2] dispatchKeyLocked.

2.1.1 resetANRTimeoutsLocked

void InputDispatcher::resetANRTimeoutsLocked() {    // 重置等待超时cause和handle    mInputTargetWaitCause = INPUT_TARGET_WAIT_CAUSE_NONE;    mInputTargetWaitApplicationHandle.clear();}

2.1.2 dropInboundEventLocked

void InputDispatcher::dropInboundEventLocked(EventEntry* entry, DropReason dropReason) {    const char* reason;    switch (dropReason) {    case DROP_REASON_POLICY:        reason = "inbound event was dropped because the policy consumed it";        break;    case DROP_REASON_DISABLED:        if (mLastDropReason != DROP_REASON_DISABLED) {            ALOGI("Dropped event because input dispatch is disabled.");        }        reason = "inbound event was dropped because input dispatch is disabled";        break;    case DROP_REASON_APP_SWITCH:        ALOGI("Dropped event because of pending overdue app switch.");        reason = "inbound event was dropped because of pending overdue app switch";        break;    case DROP_REASON_BLOCKED:        ALOGI("Dropped event because the current application is not responding and the user "                "has started interacting with a different application.");        reason = "inbound event was dropped because the current application is not responding "                "and the user has started interacting with a different application";        break;    case DROP_REASON_STALE:        ALOGI("Dropped event because it is stale.");        reason = "inbound event was dropped because it is stale";        break;    default:        return;    }    switch (entry->type) {    case EventEntry::TYPE_KEY: {        CancelationOptions options(CancelationOptions::CANCEL_NON_POINTER_EVENTS, reason);        synthesizeCancelationEventsForAllConnectionsLocked(options);        break;    }    ...    }}

2.2 dispatchKeyLocked

bool InputDispatcher::dispatchKeyLocked(nsecs_t currentTime, KeyEntry* entry,        DropReason* dropReason, nsecs_t* nextWakeupTime) {    ...    if (entry->interceptKeyResult == KeyEntry::INTERCEPT_KEY_RESULT_TRY_AGAIN_LATER) {        // case1: 当前时间小于唤醒时间，则进入等待状态。        if (currentTime < entry->interceptKeyWakeupTime) {            if (entry->interceptKeyWakeupTime < *nextWakeupTime) {                *nextWakeupTime = entry->interceptKeyWakeupTime;            }            return false; //直接返回        }        entry->interceptKeyResult = KeyEntry::INTERCEPT_KEY_RESULT_UNKNOWN;        entry->interceptKeyWakeupTime = 0;    }    if (entry->interceptKeyResult == KeyEntry::INTERCEPT_KEY_RESULT_UNKNOWN) {        //case2: 让policy有机会执行拦截操作        if (entry->policyFlags & POLICY_FLAG_PASS_TO_USER) {            CommandEntry* commandEntry = postCommandLocked(                    & InputDispatcher::doInterceptKeyBeforeDispatchingLockedInterruptible);            if (mFocusedWindowHandle != NULL) {                commandEntry->inputWindowHandle = mFocusedWindowHandle;            }            commandEntry->keyEntry = entry;            entry->refCount += 1;            return false; //直接返回        } else {            entry->interceptKeyResult = KeyEntry::INTERCEPT_KEY_RESULT_CONTINUE;        }    } else if (entry->interceptKeyResult == KeyEntry::INTERCEPT_KEY_RESULT_SKIP) {        if (*dropReason == DROP_REASON_NOT_DROPPED) {            *dropReason = DROP_REASON_POLICY;        }    }    //case3: 如果需要丢弃该事件，则执行清理操作    if (*dropReason != DROP_REASON_NOT_DROPPED) {        setInjectionResultLocked(entry, *dropReason == DROP_REASON_POLICY                ? INPUT_EVENT_INJECTION_SUCCEEDED : INPUT_EVENT_INJECTION_FAILED);        return true; //直接返回    }    Vector<InputTarget> inputTargets;    //case4: 寻找焦点 【见小节2.3】    int32_t injectionResult = findFocusedWindowTargetsLocked(currentTime,            entry, inputTargets, nextWakeupTime);    if (injectionResult == INPUT_EVENT_INJECTION_PENDING) {        return false; //直接返回    }    setInjectionResultLocked(entry, injectionResult);    if (injectionResult != INPUT_EVENT_INJECTION_SUCCEEDED) {        return true; //直接返回    }    addMonitoringTargetsLocked(inputTargets);    //只有injectionResult是成功，才有机会执行分发事件【见小节2.5】    dispatchEventLocked(currentTime, entry, inputTargets);    return true;}

在以下场景下，有可能无法分发事件：

1. 当前时间小于唤醒时间(nextWakeupTime)的情况；
2. policy需要提前拦截事件的情况；
3. 需要drop事件的情况；
4. 寻找聚焦窗口失败的情况；

如果成功跳过以上所有情况，则会进入执行事件分发的过程。

2.3 findFocusedWindowTargetsLocked

int32_t InputDispatcher::findFocusedWindowTargetsLocked(nsecs_t currentTime,        const EventEntry* entry, Vector<InputTarget>& inputTargets, nsecs_t* nextWakeupTime) {    int32_t injectionResult;    String8 reason;    if (mFocusedWindowHandle == NULL) {        if (mFocusedApplicationHandle != NULL) {            //【见小节2.3.2】            injectionResult = handleTargetsNotReadyLocked(currentTime, entry,                    mFocusedApplicationHandle, NULL, nextWakeupTime,                    "Waiting because no window has focus but there is a "                    "focused application that may eventually add a window "                    "when it finishes starting up.");            goto Unresponsive;        }        ALOGI("Dropping event because there is no focused window or focused application.");        injectionResult = INPUT_EVENT_INJECTION_FAILED;        goto Failed;    }    //权限检查    if (! checkInjectionPermission(mFocusedWindowHandle, entry->injectionState)) {        injectionResult = INPUT_EVENT_INJECTION_PERMISSION_DENIED;        goto Failed;    }    //检测窗口是否为更多的输入操作而准备就绪【见小节2.3.1】    reason = checkWindowReadyForMoreInputLocked(currentTime,            mFocusedWindowHandle, entry, "focused");    if (!reason.isEmpty()) {        //【见小节2.3.2】        injectionResult = handleTargetsNotReadyLocked(currentTime, entry,                mFocusedApplicationHandle, mFocusedWindowHandle, nextWakeupTime, reason.string());        goto Unresponsive;    }    injectionResult = INPUT_EVENT_INJECTION_SUCCEEDED;    //成功找到目标窗口，添加到目标窗口 [见小节2.3.3]    addWindowTargetLocked(mFocusedWindowHandle,            InputTarget::FLAG_FOREGROUND | InputTarget::FLAG_DISPATCH_AS_IS, BitSet32(0),            inputTargets);Failed:Unresponsive:    //TODO: 统计等待时长信息，目前没有实现，这个方法还是很值得去改造    nsecs_t timeSpentWaitingForApplication = getTimeSpentWaitingForApplicationLocked(currentTime);    updateDispatchStatisticsLocked(currentTime, entry,          injectionResult, timeSpentWaitingForApplication);    return injectionResult;}

此处mFocusedWindowHandle是何处赋值呢？是在InputDispatcher.setInputWindows()方法，具体见下一篇文章Input系统—UI线程.

寻找聚焦窗口失败的情况：

• 无窗口，无应用：Dropping event because there is no focused window or focused application.(这并不导致ANR的情况，因为没有机会调用handleTargetsNotReadyLocked)
• 无窗口, 有应用：Waiting because no window has focus but there is a focused application that may eventually add a window when it finishes starting up.

另外，还有更多多的失败场景见checkWindowReadyForMoreInputLocked的过程，如下：

2.3.1 checkWindowReadyForMoreInputLocked

String8 InputDispatcher::checkWindowReadyForMoreInputLocked(nsecs_t currentTime,        const sp<InputWindowHandle>& windowHandle, const EventEntry* eventEntry,        const char* targetType) {    //当窗口暂停的情况，则保持等待    if (windowHandle->getInfo()->paused) {        return String8::format("Waiting because the %s window is paused.", targetType);    }    //当窗口连接未注册，则保持等待    ssize_t connectionIndex = getConnectionIndexLocked(windowHandle->getInputChannel());    if (connectionIndex < 0) {        return String8::format("Waiting because the %s window's input channel is not "                "registered with the input dispatcher.  The window may be in the process "                "of being removed.", targetType);    }    //当窗口连接已死亡，则保持等待    sp<Connection> connection = mConnectionsByFd.valueAt(connectionIndex);    if (connection->status != Connection::STATUS_NORMAL) {        return String8::format("Waiting because the %s window's input connection is %s."                "The window may be in the process of being removed.", targetType,                connection->getStatusLabel());    }    // 当窗口连接已满，则保持等待    if (connection->inputPublisherBlocked) {        return String8::format("Waiting because the %s window's input channel is full.  "                "Outbound queue length: %d.  Wait queue length: %d.",                targetType, connection->outboundQueue.count(), connection->waitQueue.count());    }    if (eventEntry->type == EventEntry::TYPE_KEY) {        // 按键事件，输出队列或事件等待队列不为空        if (!connection->outboundQueue.isEmpty() || !connection->waitQueue.isEmpty()) {            return String8::format("Waiting to send key event because the %s window has not "                    "finished processing all of the input events that were previously "                    "delivered to it.  Outbound queue length: %d.  Wait queue length: %d.",                    targetType, connection->outboundQueue.count(), connection->waitQueue.count());        }    } else {        // 非按键事件，事件等待队列不为空且头事件分发超时500ms        if (!connection->waitQueue.isEmpty()                && currentTime >= connection->waitQueue.head->deliveryTime                        + STREAM_AHEAD_EVENT_TIMEOUT) {            return String8::format("Waiting to send non-key event because the %s window has not "                    "finished processing certain input events that were delivered to it over "                    "%0.1fms ago.  Wait queue length: %d.  Wait queue head age: %0.1fms.",                    targetType, STREAM_AHEAD_EVENT_TIMEOUT * 0.000001f,                    connection->waitQueue.count(),                    (currentTime - connection->waitQueue.head->deliveryTime) * 0.000001f);        }    }    return String8::empty();}

2.3.2 handleTargetsNotReadyLocked

int32_t InputDispatcher::handleTargetsNotReadyLocked(nsecs_t currentTime,    const EventEntry* entry,    const sp<InputApplicationHandle>& applicationHandle,    const sp<InputWindowHandle>& windowHandle,    nsecs_t* nextWakeupTime, const char* reason) {    if (applicationHandle == NULL && windowHandle == NULL) {        if (mInputTargetWaitCause != INPUT_TARGET_WAIT_CAUSE_SYSTEM_NOT_READY) {            mInputTargetWaitCause = INPUT_TARGET_WAIT_CAUSE_SYSTEM_NOT_READY;            mInputTargetWaitStartTime = currentTime; //当前时间            mInputTargetWaitTimeoutTime = LONG_LONG_MAX;            mInputTargetWaitTimeoutExpired = false;            mInputTargetWaitApplicationHandle.clear();        }    } else {        if (mInputTargetWaitCause != INPUT_TARGET_WAIT_CAUSE_APPLICATION_NOT_READY) {            nsecs_t timeout;            if (windowHandle != NULL) {                timeout = windowHandle->getDispatchingTimeout(DEFAULT_INPUT_DISPATCHING_TIMEOUT);            } else if (applicationHandle != NULL) {                timeout = applicationHandle->getDispatchingTimeout(DEFAULT_INPUT_DISPATCHING_TIMEOUT);            } else {                timeout = DEFAULT_INPUT_DISPATCHING_TIMEOUT; // 5s            }            mInputTargetWaitCause = INPUT_TARGET_WAIT_CAUSE_APPLICATION_NOT_READY;            mInputTargetWaitStartTime = currentTime; //当前时间            mInputTargetWaitTimeoutTime = currentTime + timeout;            mInputTargetWaitTimeoutExpired = false;            mInputTargetWaitApplicationHandle.clear();            if (windowHandle != NULL) {                mInputTargetWaitApplicationHandle = windowHandle->inputApplicationHandle;            }            if (mInputTargetWaitApplicationHandle == NULL && applicationHandle != NULL) {                mInputTargetWaitApplicationHandle = applicationHandle;            }        }    }    if (mInputTargetWaitTimeoutExpired) {        return INPUT_EVENT_INJECTION_TIMED_OUT; //等待超时已过期,则直接返回    }    //当超时5s则进入ANR流程    if (currentTime >= mInputTargetWaitTimeoutTime) {        onANRLocked(currentTime, applicationHandle, windowHandle,                entry->eventTime, mInputTargetWaitStartTime, reason);        *nextWakeupTime = LONG_LONG_MIN; //强制立刻执行轮询来执行ANR策略        return INPUT_EVENT_INJECTION_PENDING;    } else {        if (mInputTargetWaitTimeoutTime < *nextWakeupTime) {            *nextWakeupTime = mInputTargetWaitTimeoutTime; //当触发超时则强制执行轮询        }        return INPUT_EVENT_INJECTION_PENDING;    }}

此处mInputTargetWaitTimeoutTime是由当前时间戳+5s, 并设置mInputTargetWaitCause等于INPUT_TARGET_WAIT_CAUSE_APPLICATION_NOT_READY. 也就是说ANR时间段是指input等待理由处于INPUT_TARGET_WAIT_CAUSE_APPLICATION_NOT_READY(应用没有准备就绪)的时间长达5s的场景.而前面resetANRTimeoutsLocked() 过程是唯一用于重置等待理由的地方.

那么, ANR时间区间是指当前这次的事件dispatch过程中执行findFocusedWindowTargetsLocked()方法到下一次执行resetANRTimeoutsLocked()的时间区间.

• 当applicationHandle和windowHandle同时为空, 且system准备就绪的情况下
  • 设置等待理由 INPUT_TARGET_WAIT_CAUSE_SYSTEM_NOT_READY;
  • 设置超时等待时长为无限大;
  • 设置TimeoutExpired= false
  • 清空等待队列;
• 当applicationHandle和windowHandle至少一个不为空, 且application准备就绪的情况下:
  • 设置等待理由 INPUT_TARGET_WAIT_CAUSE_APPLICATION_NOT_READY;
  • 设置超时等待时长为5s;
  • 设置TimeoutExpired= false
  • 清空等待队列;

继续回到[小节2.3]findFocusedWindowTargetsLocked，如果没有发生ANR，则addWindowTargetLocked()将该事件添加到inputTargets。

2.3.3 addWindowTargetLocked

void InputDispatcher::addWindowTargetLocked(const sp<InputWindowHandle>& windowHandle,        int32_t targetFlags, BitSet32 pointerIds, Vector<InputTarget>& inputTargets) {    inputTargets.push();    const InputWindowInfo* windowInfo = windowHandle->getInfo();    InputTarget& target = inputTargets.editTop();    target.inputChannel = windowInfo->inputChannel;    target.flags = targetFlags;    target.xOffset = - windowInfo->frameLeft;    target.yOffset = - windowInfo->frameTop;    target.scaleFactor = windowInfo->scaleFactor;    target.pointerIds = pointerIds;}

将当前聚焦窗口mFocusedWindowHandle的inputChannel传递到inputTargets。

2.4 dispatchEventLocked

void InputDispatcher::dispatchEventLocked(nsecs_t currentTime,        EventEntry* eventEntry, const Vector<InputTarget>& inputTargets) {    //【见小节2.4.1】向mCommandQueue队列添加doPokeUserActivityLockedInterruptible命令    pokeUserActivityLocked(eventEntry);    for (size_t i = 0; i < inputTargets.size(); i++) {        const InputTarget& inputTarget = inputTargets.itemAt(i);        //[见小节2.4.3]        ssize_t connectionIndex = getConnectionIndexLocked(inputTarget.inputChannel);        if (connectionIndex >= 0) {            sp<Connection> connection = mConnectionsByFd.valueAt(connectionIndex);            //找到目标连接[见小节２.5]            prepareDispatchCycleLocked(currentTime, connection, eventEntry, &inputTarget);        }    }}

该方法主要功能是将eventEntry发送到目标inputTargets．

其中pokeUserActivityLocked(eventEntry)方法最终会调用到Java层的PowerManagerService.java中的userActivityFromNative()方法． 这也是PMS中唯一的native call方法．

2.4.1 pokeUserActivityLocked

void InputDispatcher::pokeUserActivityLocked(const EventEntry* eventEntry) {    if (mFocusedWindowHandle != NULL) {        const InputWindowInfo* info = mFocusedWindowHandle->getInfo();        if (info->inputFeatures & InputWindowInfo::INPUT_FEATURE_DISABLE_USER_ACTIVITY) {            return;        }    }    ...    //【见小节2.4.2】    CommandEntry* commandEntry = postCommandLocked(            & InputDispatcher::doPokeUserActivityLockedInterruptible);    commandEntry->eventTime = eventEntry->eventTime;    commandEntry->userActivityEventType = eventType;}

2.4.2 postCommandLocked

InputDispatcher::CommandEntry* InputDispatcher::postCommandLocked(Command command) {    CommandEntry* commandEntry = new CommandEntry(command);    // 将命令加入mCommandQueue队尾    mCommandQueue.enqueueAtTail(commandEntry);    return commandEntry;}

2.4.3 getConnectionIndexLocked

ssize_t InputDispatcher::getConnectionIndexLocked(const sp<InputChannel>& inputChannel) {    ssize_t connectionIndex = mConnectionsByFd.indexOfKey(inputChannel->getFd());    if (connectionIndex >= 0) {        sp<Connection> connection = mConnectionsByFd.valueAt(connectionIndex);        if (connection->inputChannel.get() == inputChannel.get()) {            return connectionIndex;        }    }    return -1;}

根据inputChannel的fd从mConnectionsByFd队列中查询目标connection.

2.5 prepareDispatchCycleLocked

void InputDispatcher::prepareDispatchCycleLocked(nsecs_t currentTime,        const sp<Connection>& connection, EventEntry* eventEntry, const InputTarget* inputTarget) {    if (connection->status != Connection::STATUS_NORMAL) {        return;　//当连接已破坏,则直接返回    }    ...    //[见小节2.6]    enqueueDispatchEntriesLocked(currentTime, connection, eventEntry, inputTarget);}

当connection状态不正确，则直接返回。

2.6 enqueueDispatchEntriesLocked

void InputDispatcher::enqueueDispatchEntriesLocked(nsecs_t currentTime,        const sp<Connection>& connection, EventEntry* eventEntry, const InputTarget* inputTarget) {    bool wasEmpty = connection->outboundQueue.isEmpty();    //[见小节2.7]    enqueueDispatchEntryLocked(connection, eventEntry, inputTarget,            InputTarget::FLAG_DISPATCH_AS_HOVER_EXIT);    enqueueDispatchEntryLocked(connection, eventEntry, inputTarget,            InputTarget::FLAG_DISPATCH_AS_OUTSIDE);    enqueueDispatchEntryLocked(connection, eventEntry, inputTarget,            InputTarget::FLAG_DISPATCH_AS_HOVER_ENTER);    enqueueDispatchEntryLocked(connection, eventEntry, inputTarget,            InputTarget::FLAG_DISPATCH_AS_IS);    enqueueDispatchEntryLocked(connection, eventEntry, inputTarget,            InputTarget::FLAG_DISPATCH_AS_SLIPPERY_EXIT);    enqueueDispatchEntryLocked(connection, eventEntry, inputTarget,            InputTarget::FLAG_DISPATCH_AS_SLIPPERY_ENTER);    if (wasEmpty && !connection->outboundQueue.isEmpty()) {        //当原先的outbound队列为空, 且当前outbound不为空的情况执行.[见小节2.8]        startDispatchCycleLocked(currentTime, connection);    }}

该方法主要功能：

• 根据dispatchMode来分别执行DispatchEntry事件加入队列的操作。
• 当起初connection.outboundQueue等于空, 经enqueueDispatchEntryLocked处理后, outboundQueue不等于空情况下, 则执行startDispatchCycleLocked()方法.

2.7 enqueueDispatchEntryLocked

void InputDispatcher::enqueueDispatchEntryLocked(        const sp<Connection>& connection, EventEntry* eventEntry, const InputTarget* inputTarget,        int32_t dispatchMode) {    int32_t inputTargetFlags = inputTarget->flags;    if (!(inputTargetFlags & dispatchMode)) {        return; //分发模式不匹配,则直接返回    }    inputTargetFlags = (inputTargetFlags & ~InputTarget::FLAG_DISPATCH_MASK) | dispatchMode;    //生成新的事件, 加入connection的outbound队列    DispatchEntry* dispatchEntry = new DispatchEntry(eventEntry,            inputTargetFlags, inputTarget->xOffset, inputTarget->yOffset,            inputTarget->scaleFactor);    switch (eventEntry->type) {        case EventEntry::TYPE_KEY: {            KeyEntry* keyEntry = static_cast<KeyEntry*>(eventEntry);            dispatchEntry->resolvedAction = keyEntry->action;            dispatchEntry->resolvedFlags = keyEntry->flags;            if (!connection->inputState.trackKey(keyEntry,                    dispatchEntry->resolvedAction, dispatchEntry->resolvedFlags)) {                delete dispatchEntry;                return; //忽略不连续的事件            }            break;        }        ...    }    ...    //添加到outboundQueue队尾    connection->outboundQueue.enqueueAtTail(dispatchEntry);}

该方法主要功能:

• 根据dispatchMode来决定是否需要加入outboundQueue队列;
• 根据EventEntry,来生成DispatchEntry事件;
• 将dispatchEntry加入到connection的outbound队列.

执行到这里,其实等于由做了一次搬运的工作,将InputDispatcher中mInboundQueue中的事件取出后, 找到目标window后,封装dispatchEntry加入到connection的outbound队列.

2.8 startDispatchCycleLocked

void InputDispatcher::startDispatchCycleLocked(nsecs_t currentTime,        const sp<Connection>& connection) {    //当Connection状态正常,且outboundQueue不为空    while (connection->status == Connection::STATUS_NORMAL            && !connection->outboundQueue.isEmpty()) {        DispatchEntry* dispatchEntry = connection->outboundQueue.head;        dispatchEntry->deliveryTime = currentTime; //设置deliveryTime时间        status_t status;        EventEntry* eventEntry = dispatchEntry->eventEntry;        switch (eventEntry->type) {          case EventEntry::TYPE_KEY: {              KeyEntry* keyEntry = static_cast<KeyEntry*>(eventEntry);              //发布Key事件 [见小节2.9]              status = connection->inputPublisher.publishKeyEvent(dispatchEntry->seq,                      keyEntry->deviceId, keyEntry->source,                      dispatchEntry->resolvedAction, dispatchEntry->resolvedFlags,                      keyEntry->keyCode, keyEntry->scanCode,                      keyEntry->metaState, keyEntry->repeatCount, keyEntry->downTime,                      keyEntry->eventTime);              break;          }          ...        }        if (status) { //publishKeyEvent失败情况            if (status == WOULD_BLOCK) {                if (connection->waitQueue.isEmpty()) {                    //pipe已满,但waitQueue为空. 不正常的行为                    abortBrokenDispatchCycleLocked(currentTime, connection, true /*notify*/);                } else {                    // 处于阻塞状态                    connection->inputPublisherBlocked = true;                }            } else {                //不不正常的行为                abortBrokenDispatchCycleLocked(currentTime, connection, true /*notify*/);            }            return;        }        //从outboundQueue中取出事件,重新放入waitQueue队列        connection->outboundQueue.dequeue(dispatchEntry);        connection->waitQueue.enqueueAtTail(dispatchEntry);    }}

startDispatchCycleLocked的主要功能: 从outboundQueue中取出事件,重新放入waitQueue队列

• startDispatchCycleLocked触发时机：当起初connection.outboundQueue等于空, 经enqueueDispatchEntryLocked处理后, outboundQueue不等于空。
• startDispatchCycleLocked主要功能: 从outboundQueue中取出事件,重新放入waitQueue队列
• publishKeyEvent执行结果status不等于OK的情况下：
  • WOULD_BLOCK，且waitQueue等于空，则调用abortBrokenDispatchCycleLocked()，该方法最终会调用到Java层的IMS.notifyInputChannelBroken().
  • WOULD_BLOCK，且waitQueue不等于空，则处于阻塞状态，即inputPublisherBlocked=true
  • 其他情况，则调用abortBrokenDispatchCycleLocked
• abortBrokenDispatchCycleLocked()方法最终会调用到Java层的IMS.notifyInputChannelBroken().

2.9 inputPublisher.publishKeyEvent

[-> InputTransport.cpp]

status_t InputPublisher::publishKeyEvent(...) {    if (!seq) {        return BAD_VALUE;    }    InputMessage msg;    msg.header.type = InputMessage::TYPE_KEY;    msg.body.key.seq = seq;    msg.body.key.deviceId = deviceId;    msg.body.key.source = source;    msg.body.key.action = action;    msg.body.key.flags = flags;    msg.body.key.keyCode = keyCode;    msg.body.key.scanCode = scanCode;    msg.body.key.metaState = metaState;    msg.body.key.repeatCount = repeatCount;    msg.body.key.downTime = downTime;    msg.body.key.eventTime = eventTime;    //通过InputChannel来发送消息    return mChannel->sendMessage(&msg);}

InputChannel通过socket向远端的socket发送消息。socket通道是如何建立的呢？ InputDispatcher又是如何与前台的window通信的呢？ 见下一篇文章Input系统—进程交互, 从文章的小节2.1开始继续往下说.

2.10 releasePendingEventLocked

void InputDispatcher::releasePendingEventLocked() {    if (mPendingEvent) {        resetANRTimeoutsLocked(); //重置ANR超时时间        releaseInboundEventLocked(mPendingEvent); //释放mPendingEvent对象,并记录到mRecentQueue队列        mPendingEvent = NULL; //置空mPendingEvent变量.    }}

三. 处理Comand

3.1 runCommandsLockedInterruptible

bool InputDispatcher::runCommandsLockedInterruptible() {    if (mCommandQueue.isEmpty()) {        return false;    }    do {        //从mCommandQueue队列的头部取出第一个元素        CommandEntry* commandEntry = mCommandQueue.dequeueAtHead();        Command command = commandEntry->command;        //此处调用的命令隐式地包含'LockedInterruptible'        (this->*command)(commandEntry);        commandEntry->connection.clear();        delete commandEntry;    } while (! mCommandQueue.isEmpty());    return true;}

通过循环方式处理完mCommandQueue队列的所有命令，处理过程从mCommandQueue中取出CommandEntry.

typedef void (InputDispatcher::*Command)(CommandEntry* commandEntry);struct CommandEntry : Link<CommandEntry> {    CommandEntry(Command command);    Command command;    sp<Connection> connection;    nsecs_t eventTime;    KeyEntry* keyEntry;    sp<InputApplicationHandle> inputApplicationHandle;    sp<InputWindowHandle> inputWindowHandle;    String8 reason;    int32_t userActivityEventType;    uint32_t seq;    bool handled;};

前面小节【2.4.1】添加的doPokeUserActivityLockedInterruptible命令. 接下来进入该方法：

3.2 doPokeUserActivityLockedInterruptible

[-> InputDispatcher]

void InputDispatcher::doPokeUserActivityLockedInterruptible(CommandEntry* commandEntry) {    mLock.unlock();    //【见小节4.3】    mPolicy->pokeUserActivity(commandEntry->eventTime, commandEntry->userActivityEventType);    mLock.lock();}

3.3 pokeUserActivity

[-> com_android_server_input_InputManagerService.cpp]

void NativeInputManager::pokeUserActivity(nsecs_t eventTime, int32_t eventType) {    //[见小节4.4]    android_server_PowerManagerService_userActivity(eventTime, eventType);}

3.4 android_server_PowerManagerService_userActivity

[-> com_android_server_power_PowerManagerService.cpp]

void android_server_PowerManagerService_userActivity(nsecs_t eventTime, int32_t eventType) {    // Tell the power HAL when user activity occurs.    if (gPowerModule && gPowerModule->powerHint) {        gPowerModule->powerHint(gPowerModule, POWER_HINT_INTERACTION, NULL);    }    if (gPowerManagerServiceObj) {        ...        //[见小节4.5]        env->CallVoidMethod(gPowerManagerServiceObj,                gPowerManagerServiceClassInfo.userActivityFromNative,                nanoseconds_to_milliseconds(eventTime), eventType, 0);    }}

3.5 PMS.userActivityFromNative

[-> PowerManagerService.java]

private void userActivityFromNative(long eventTime, int event, int flags) {    userActivityInternal(eventTime, event, flags, Process.SYSTEM_UID);}private void userActivityInternal(long eventTime, int event, int flags, int uid) {    synchronized (mLock) {        if (userActivityNoUpdateLocked(eventTime, event, flags, uid)) {            updatePowerStateLocked();        }    }}

runCommandsLockedInterruptible是不断地从mCommandQueue队列取出命令，然后执行直到全部执行完成。 除了doPokeUserActivityLockedInterruptible，还有其他如下命令：

• doNotifyANRLockedInterruptible
• doInterceptKeyBeforeDispatchingLockedInterruptible
• doDispatchCycleFinishedLockedInterruptible
• doNotifyInputChannelBrokenLockedInterruptible
• doNotifyConfigurationChangedInterruptible

四. 总结

4.1 流程图

点击查看大图:

4.2 核心方法

用一张图来整体概况InputDispatcher线程的主要工作：

图解:

1. dispatchOnceInnerLocked(): 从InputDispatcher的mInboundQueue队列，取出事件EventEntry。另外该方法开始执行的时间点(currentTime)便是后续事件dispatchEntry的分发时间(deliveryTime）
2. dispatchKeyLocked()：满足一定条件时会添加命令doInterceptKeyBeforeDispatchingLockedInterruptible；
3. enqueueDispatchEntryLocked()：生成事件DispatchEntry并加入connection的outbound队列
4. startDispatchCycleLocked()：从outboundQueue中取出事件DispatchEntry, 重新放入connection的waitQueue队列；
5. InputChannel.sendMessage通过socket方式将消息发送给远程进程；
6. runCommandsLockedInterruptible()：通过循环遍历地方式，依次处理mCommandQueue队列中的所有命令。而mCommandQueue队列中的命令是通过postCommandLocked()方式向该队列添加的。

一. 概述

前面文章都是介绍了两个线程InputReader和InputDispatcher的工作过程。在InputDispatcher的过程讲到 调用InputChanel通过socket与远程进程通信，本文便展开讲解这个socket是如何建立的。

对于InputReader和InputDispatcher都是运行在system_server进程； 用户点击的界面往往可能是某一个app，而每个app一般地都运行在自己的进程，这里就涉及到跨进程通信，app进程是如何与system进程建立通信。

要解答这些问题，从Activity最基本的创建过程开始说起。我们都知道一般地Activity对应一个应用窗口, 每一个窗口对应一个ViewRootImpl。窗口是如何添加到Activity的，从Activity.onCreate()为起点讲解。

二. UI线程

总所周知，Activity的生命周期的回调方法都是运行在主线程，也称之为UI线程，所有UI相关的操作都需要运行在该线程。本文虽然是UI线程，但并非只介绍所有运行在UI线程的流程，文中还涉及binder thread。

2.1 onCreate

[-> Activity.java]

protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_account_bind);    ...}

Activity启动是由system进程控制：

1. handleLaunchActivity()：会调用Activity.onCreate(), 该方法内再调用setContentView(),经过AMS与WMS的各种交互,层层调用后,进入step2
2. handleResumeActivity()：会调用Activity.makeVisible(),该方法继续调用便会执行到WindowManagerImpl.addView(), 该方法内部再调用WindowManagerGlobal.addView(),

2.2 addView

[-> WindowManagerGlobal.java]

public void addView(View view, ViewGroup.LayoutParams params,        Display display, Window parentWindow) {    ...    //[见小节2.3]    ViewRootImpl root = new ViewRootImpl(view.getContext(), display);    //[见小节2.3.3]    root.setView(view, wparams, panelParentView);    ...}

2.3 ViewRootImpl

[-> ViewRootImpl.java]

public ViewRootImpl(Context context, Display display) {    mContext = context;    //获取IWindowSession的代理类【见小节2.3.1】    mWindowSession = WindowManagerGlobal.getWindowSession();    mDisplay = display;    mThread = Thread.currentThread(); //主线程    mWindow = new W(this);    mChoreographer = Choreographer.getInstance();    ...}

2.3.1 getWindowSession

[-> WindowManagerGlobal.java]

public static IWindowSession getWindowSession() {    synchronized (WindowManagerGlobal.class) {        if (sWindowSession == null) {            try {                //获取IMS的代理类                InputMethodManager imm = InputMethodManager.getInstance();                //获取WMS的代理类                IWindowManager windowManager = getWindowManagerService();                //经过Binder调用，最终调用WMS[见小节2.3.2]                sWindowSession = windowManager.openSession(                        new IWindowSessionCallback.Stub() {...},                        imm.getClient(), imm.getInputContext());            } catch (RemoteException e) {                ...            }        }        return sWindowSession    }}

2.3.2 WMS.openSession

public IWindowSession openSession(IWindowSessionCallback callback, IInputMethodClient client,        IInputContext inputContext) {    //创建Session对象    Session session = new Session(this, callback, client, inputContext);    return session;}

再次经过Binder将数据写回app进程，则获取的便是Session的代理对象。

2.3.3 setView

[-> ViewRootImpl.java]

public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {    synchronized (this) {      ...      if ((mWindowAttributes.inputFeatures          & WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {          mInputChannel = new InputChannel(); //创建InputChannel对象      }      //通过Binder调用，进入system进程的Session[见小节2.4]      res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,                  getHostVisibility(), mDisplay.getDisplayId(),                  mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,                  mAttachInfo.mOutsets, mInputChannel);      ...      if (mInputChannel != null) {          if (mInputQueueCallback != null) {              mInputQueue = new InputQueue();              mInputQueueCallback.onInputQueueCreated(mInputQueue);          }          //创建WindowInputEventReceiver对象[见3.1]          mInputEventReceiver = new WindowInputEventReceiver(mInputChannel,                  Looper.myLooper());      }    }}

该方法主要功能:

1. 创建Java层的InputChannel对象mInputChannel
2. 向WMS注册InputChannel信息，通过InputChannel.openInputChannelPair创建的socket pair，将其中的客户端赋值给mInputChannel.
3. 创建WindowInputEventReceiver对象

跨进程调用，进入binder thread执行如下方法：

2.4 Session.addToDisplay

[-> Session.java]

final class Session extends IWindowSession.Stub implements IBinder.DeathRecipient {    public int addToDisplay(IWindow window, int seq, WindowManager.LayoutParams attrs,            int viewVisibility, int displayId, Rect outContentInsets, Rect outStableInsets,            Rect outOutsets, InputChannel outInputChannel) {        //[见小节2.5]        return mService.addWindow(this, window, seq, attrs, viewVisibility, displayId,                outContentInsets, outStableInsets, outOutsets, outInputChannel);    }}

2.5 WMS.addToDisplay

[-> WindowManagerService.java]

public int addWindow(Session session, IWindow client, int seq,           WindowManager.LayoutParams attrs, int viewVisibility, int displayId,           Rect outContentInsets, Rect outStableInsets, Rect outOutsets,           InputChannel outInputChannel) {    ...    //创建WindowState【见小节2.5.1】    WindowState win = new WindowState(this, session, client, token,                attachedWindow, appOp[0], seq, attrs, viewVisibility, displayContent);                    if (outInputChannel != null && (attrs.inputFeatures            & WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {         //根据WindowState的HashCode以及title来生成InputChannel名称        String name = win.makeInputChannelName();                //创建一对InputChannel[见小节2.6]        InputChannel[] inputChannels = InputChannel.openInputChannelPair(name);        //将socket服务端保存到WindowState的mInputChannel        win.setInputChannel(inputChannels[0]);                //socket客户端传递给outInputChannel [见小节2.7]        inputChannels[1].transferTo(outInputChannel);        //利用socket服务端作为参数[见小节2.8]        mInputManager.registerInputChannel(win.mInputChannel, win.mInputWindowHandle);    }    ...    boolean focusChanged = false;    if (win.canReceiveKeys()) {        //新添加window能接收按下操作，则更新聚焦窗口。        focusChanged = updateFocusedWindowLocked(UPDATE_FOCUS_WILL_ASSIGN_LAYERS,                false /*updateInputWindows*/);    }    ...        if (focusChanged) {        mInputMonitor.setInputFocusLw(mCurrentFocus, false /*updateInputWindows*/);    }    //设置当前聚焦窗口【见小节2.5.2】    mInputMonitor.updateInputWindowsLw(false /*force*/);}

inputChannels数组：

• inputChannels[0]所对应的InputChannel名称的后缀为(server);
• inputChannels[1]所对应的InputChannel名称的后缀为(client)；

其中：

• 服务端inputChannels[0]保存到WindowState的mInputChannel；
• 客户端inputChannels[1]传递给outInputChannel，最终传递给ViewRootImpl的mInputChannel；

2.5.1 WindowState初始化

[-> WindowState.java]

WindowState(WindowManagerService service, Session s, IWindow c, WindowToken token,       WindowState attachedWindow, int appOp, int seq, WindowManager.LayoutParams a,       int viewVisibility, final DisplayContent displayContent) {    ...    WindowState appWin = this;    while (appWin.mAttachedWindow != null) {       appWin = appWin.mAttachedWindow;    }    WindowToken appToken = appWin.mToken;    while (appToken.appWindowToken == null) {       WindowToken parent = mService.mTokenMap.get(appToken.token);       if (parent == null || appToken == parent) {           break;       }       appToken = parent;    }    mAppToken = appToken.appWindowToken;    //创建InputWindowHandle对象    mInputWindowHandle = new InputWindowHandle(            mAppToken != null ? mAppToken.mInputApplicationHandle : null, this,            displayContent.getDisplayId());}

2.5.2 updateInputWindowsLw

[-> InputMonitor.java]

public void updateInputWindowsLw(boolean force) {    ...    final InputWindowHandle dragWindowHandle = mService.mDragState.mDragWindowHandle;    if (dragWindowHandle != null) {        //将dragWindowHandle赋值给mInputWindowHandles        addInputWindowHandleLw(dragWindowHandle);    }     ...    //将当前mInputWindowHandles传递到native【】    mService.mInputManager.setInputWindows(mInputWindowHandles);    ...}

setInputWindows的调用链：(最终设置mFocusedWindowHandle值)

-> IMS.setInputWindows   -> NativeInputManager::setInputWindows    -> InputDispatcher::setInputWindows

dragWindowHandle的初始化过程：

View.startDrag    Session.prepareDrag      WMS.prepareDragSurface        mDragState = new DragState(...);    Session.performDrag         DragState.register        mDragWindowHandle = new InputWindowHandle(...);   

2.6 openInputChannelPair

[-> InputChannel.java]

public static InputChannel[] openInputChannelPair(String name) {    return nativeOpenInputChannelPair(name);}

这个过程的主要功能

1. 创建两个socket通道(非阻塞, buffer上限32KB)
2. 创建两个InputChannel对象;
3. 创建两个NativeInputChannel对象;
4. 将nativeInputChannel保存到Java层的InputChannel的成员变量mPtr

2.6.1 nativeOpenInputChannelPair

[-> android_view_InputChannel.cpp]

static jobjectArray android_view_InputChannel_nativeOpenInputChannelPair(JNIEnv* env,        jclass clazz, jstring nameObj) {    const char* nameChars = env->GetStringUTFChars(nameObj, NULL);    String8 name(nameChars);    env->ReleaseStringUTFChars(nameObj, nameChars);    sp<InputChannel> serverChannel;    sp<InputChannel> clientChannel;    //创建一对socket[见小节2.6.2]    status_t result = InputChannel::openInputChannelPair(name, serverChannel, clientChannel);    //创建Java数组    jobjectArray channelPair = env->NewObjectArray(2, gInputChannelClassInfo.clazz, NULL);    ...    //创建NativeInputChannel对象[见小节2.6.3]    jobject serverChannelObj = android_view_InputChannel_createInputChannel(env,            new NativeInputChannel(serverChannel));    ...        //创建NativeInputChannel对象[见小节2.6.3]    jobject clientChannelObj = android_view_InputChannel_createInputChannel(env,            new NativeInputChannel(clientChannel));    ...        //将client和server 两个插入到channelPair    env->SetObjectArrayElement(channelPair, 0, serverChannelObj);    env->SetObjectArrayElement(channelPair, 1, clientChannelObj);    return channelPair;}

2.6.2 openInputChannelPair

[-> InputTransport.cpp]

status_t InputChannel::openInputChannelPair(const String8& name,        sp<InputChannel>& outServerChannel, sp<InputChannel>& outClientChannel) {    int sockets[2];    //真正创建socket对的地方【核心】    if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sockets)) {        ...        return result;    }    int bufferSize = SOCKET_BUFFER_SIZE; //32k    setsockopt(sockets[0], SOL_SOCKET, SO_SNDBUF, &bufferSize, sizeof(bufferSize));    setsockopt(sockets[0], SOL_SOCKET, SO_RCVBUF, &bufferSize, sizeof(bufferSize));    setsockopt(sockets[1], SOL_SOCKET, SO_SNDBUF, &bufferSize, sizeof(bufferSize));    setsockopt(sockets[1], SOL_SOCKET, SO_RCVBUF, &bufferSize, sizeof(bufferSize));    String8 serverChannelName = name;    serverChannelName.append(" (server)");    //创建InputChannel对象    outServerChannel = new InputChannel(serverChannelName, sockets[0]);    String8 clientChannelName = name;    clientChannelName.append(" (client)");    //创建InputChannel对象    outClientChannel = new InputChannel(clientChannelName, sockets[1]);    return OK;}

该方法主要功能:

1. 创建socket pair; (非阻塞式的socket)
2. 设置两个socket的接收和发送的buffer上限为32KB;
3. 创建client和server的Native层InputChannel对象;
   • sockets[0]所对应的InputChannel名称的后缀为(server);
   • sockets[1]所对应的InputChannel名称的后缀为(client)

创建InputChannel对象位于文件InputTransport.cpp，如下：

InputChannel::InputChannel(const String8& name, int fd) :        mName(name), mFd(fd) {    //将socket设置成非阻塞方式    int result = fcntl(mFd, F_SETFL, O_NONBLOCK);}

另外，创建NativeInputChannel对象位于文件android_view_InputChannel.cpp，如下：

NativeInputChannel::NativeInputChannel(const sp<InputChannel>& inputChannel) :  mInputChannel(inputChannel), mDisposeCallback(NULL) {}

2.6.3 android_view_InputChannel_createInputChannel

[-> android_view_InputChannel.cpp]

static jobject android_view_InputChannel_createInputChannel(JNIEnv* env,        NativeInputChannel* nativeInputChannel) {    //创建Java的InputChannel    jobject inputChannelObj = env->NewObject(gInputChannelClassInfo.clazz,            gInputChannelClassInfo.ctor);    if (inputChannelObj) {        //将nativeInputChannel保存到Java层的InputChannel的成员变量mPtr        android_view_InputChannel_setNativeInputChannel(env, inputChannelObj, nativeInputChannel);    }    return inputChannelObj;}static void android_view_InputChannel_setNativeInputChannel(JNIEnv* env, jobject inputChannelObj,        NativeInputChannel* nativeInputChannel) {    env->SetLongField(inputChannelObj, gInputChannelClassInfo.mPtr,             reinterpret_cast<jlong>(nativeInputChannel));}

此处:

• gInputChannelClassInfo.clazz是指Java层的InputChannel类
• gInputChannelClassInfo.ctor是指Java层的InputChannel构造方法;
• gInputChannelClassInfo.mPtr是指Java层的InputChannel的成员变量mPtr;

2.7 transferTo

[-> InputChannel.java]

public void transferTo(InputChannel outParameter) {        nativeTransferTo(outParameter);}

2.7.1 nativeTransferTo

[-> android_view_InputChannel.cpp]

static void android_view_InputChannel_nativeTransferTo(JNIEnv* env, jobject obj,        jobject otherObj) {        if (android_view_InputChannel_getNativeInputChannel(env, otherObj) != NULL) {        return; //当Java层的InputChannel.mPtr不为空,则返回    }        //将当前inputChannels[1]的mPtr赋值给nativeInputChannel    NativeInputChannel* nativeInputChannel =            android_view_InputChannel_getNativeInputChannel(env, obj);    // 将该nativeInputChannel保存到outInputChannel的参数    android_view_InputChannel_setNativeInputChannel(env, otherObj, nativeInputChannel);    android_view_InputChannel_setNativeInputChannel(env, obj, NULL);}

inputChannels[1].transferTo(outInputChannel)主要功能:

1. 当outInputChannel.mPtr不为空,则直接返回;否则进入step2;
2. 将inputChannels[1].mPtr的值赋给outInputChannel.mPtr;
3. 清空inputChannels[1].mPtr值;

也就是将socket客户端inputChannels[1]传递给outInputChannel；

2.8 IMS.registerInputChannel

[-> InputManagerService.java]

public void registerInputChannel(InputChannel inputChannel,        InputWindowHandle inputWindowHandle) {    nativeRegisterInputChannel(mPtr, inputChannel, inputWindowHandle, false);}

• inputChannel是指inputChannels[0],即socket服务端；
• inputWindowHandle是指WindowState.mInputWindowHandle;

2.8.1 nativeRegisterInputChannel

[-> com_android_server_input_InputManagerService.cpp]

static void nativeRegisterInputChannel(JNIEnv* env, jclass /* clazz */,        jlong ptr, jobject inputChannelObj, jobject inputWindowHandleObj, jboolean monitor) {    NativeInputManager* im = reinterpret_cast<NativeInputManager*>(ptr);    sp<InputChannel> inputChannel = android_view_InputChannel_getInputChannel(env,            inputChannelObj);    sp<InputWindowHandle> inputWindowHandle =            android_server_InputWindowHandle_getHandle(env, inputWindowHandleObj);        //[见小节2.8.2]    status_t status = im->registerInputChannel(            env, inputChannel, inputWindowHandle, monitor);    ...    if (! monitor) {        android_view_InputChannel_setDisposeCallback(env, inputChannelObj,                handleInputChannelDisposed, im);    }}

2.8.2 registerInputChannel

[-> com_android_server_input_InputManagerService.cpp]

status_t NativeInputManager::registerInputChannel(JNIEnv* /* env */,        const sp<InputChannel>& inputChannel,        const sp<InputWindowHandle>& inputWindowHandle, bool monitor) {    //[见小节2.8.3]    return mInputManager->getDispatcher()->registerInputChannel(            inputChannel, inputWindowHandle, monitor);}

mInputManager是指NativeInputManager初始化过程创建的InputManager对象(C++).

2.8.3 registerInputChannel

[-> InputDispatcher.cpp]

status_t InputDispatcher::registerInputChannel(const sp<InputChannel>& inputChannel,        const sp<InputWindowHandle>& inputWindowHandle, bool monitor) {    {         AutoMutex _l(mLock);        ...                //创建Connection[见小节2.8.4]        sp<Connection> connection = new Connection(inputChannel, inputWindowHandle, monitor);        int fd = inputChannel->getFd();        mConnectionsByFd.add(fd, connection);        ...        //将该fd添加到Looper监听[见小节2.8.5]        mLooper->addFd(fd, 0, ALOOPER_EVENT_INPUT, handleReceiveCallback, this);    }    mLooper->wake(); //connection改变, 则唤醒looper    return OK;}

将新创建的connection保存到mConnectionsByFd成员变量，“InputDispatcher”线程的Looper添加对socket服务端的监听功能； 当该socket有消息时便会唤醒该线程工作。

2.8.4 初始化Connection

[-> InputDispatcher.cpp]

InputDispatcher::Connection::Connection(const sp<InputChannel>& inputChannel,        const sp<InputWindowHandle>& inputWindowHandle, bool monitor) :        status(STATUS_NORMAL), inputChannel(inputChannel), inputWindowHandle(inputWindowHandle),        monitor(monitor),        inputPublisher(inputChannel), inputPublisherBlocked(false) {}

其中InputPublisher初始化位于文件InputTransport.cpp

InputPublisher:: InputPublisher(const sp<InputChannel>& channel) :        mChannel(channel) {}

此处inputChannel是指前面openInputChannelPair创建的socket服务端，将其同时保存到Connection.inputChannel和InputPublisher.mChannel。

2.8.5 Looper.addFd

[-> system/core/libutils/Looper.cpp]

int Looper::addFd(int fd, int ident, int events, Looper_callbackFunc callback, void* data) {    // 此处的callback为handleReceiveCallback     return addFd(fd, ident, events, callback ? new SimpleLooperCallback(callback) : NULL, data);}int Looper::addFd(int fd, int ident, int events, const sp<LooperCallback>& callback, void* data) {    {        AutoMutex _l(mLock);        Request request;        request.fd = fd;        request.ident = ident;        request.events = events;        request.seq = mNextRequestSeq++;        request.callback = callback; //是指SimpleLooperCallback        request.data = data;        if (mNextRequestSeq == -1) mNextRequestSeq = 0;                struct epoll_event eventItem;        request.initEventItem(&eventItem);        ssize_t requestIndex = mRequests.indexOfKey(fd);        if (requestIndex < 0) {            //通过epoll监听fd            int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, fd, & eventItem);            ...            mRequests.add(fd, request); //该fd的request加入到mRequests队列        } else {            int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_MOD, fd, & eventItem);            ...            mRequests.replaceValueAt(requestIndex, request);        }    }     return 1;}

此处Loop便是“InputDispatcher”线程的Looper，将socket服务端的fd采用epoll机制注册监听.

小节

虽然本文介绍的UI线程的工作，

• [小节2.1 ~ 2.3]： 运行在UI线程；
• [小节2.4 ~ 2.8]：通过IWindowSession的Binder IPC调用，运行在system_server的binder thread;

ViewRootImpl的setView()过程:

• 创建socket pair，作为InputChannel:
  • socket服务端保存到system_server中的WindowState的mInputChannel；
  • socket客户端通过binder传回到远程进程的UI主线程ViewRootImpl的mInputChannel；
• IMS.registerInputChannel()注册InputChannel，监听socket服务端：
  • Loop便是“InputDispatcher”线程的Looper;
  • 回调方法handleReceiveCallback。

三. WindowInputEventReceiver

接下来，看看【小节2.3.3】创建WindowInputEventReceiver对象

3.1 WindowInputEventReceiver初始化

[-> ViewRootImpl.java]

final class WindowInputEventReceiver extends InputEventReceiver {    //inputChannel是指socket客户端，Looper是指UI线程的Looper    public WindowInputEventReceiver(InputChannel inputChannel, Looper looper) {        super(inputChannel, looper); //【见小节3.2】    }    ...}

3.2 InputEventReceiver

[-> InputEventReceiver.java]

public InputEventReceiver(InputChannel inputChannel, Looper looper) {     ...     mInputChannel = inputChannel;     mMessageQueue = looper.getQueue(); //UI线程消息队列     //【加小节3.3】     mReceiverPtr = nativeInit(new WeakReference<InputEventReceiver>(this),             inputChannel, mMessageQueue); }

3.3 nativeInit

[-> android_view_InputEventReceiver.cpp]

static jlong nativeInit(JNIEnv* env, jclass clazz, jobject receiverWeak,        jobject inputChannelObj, jobject messageQueueObj) {    sp<InputChannel> inputChannel = android_view_InputChannel_getInputChannel(env,            inputChannelObj);    //获取UI主线程的消息队列    sp<MessageQueue> messageQueue = android_os_MessageQueue_getMessageQueue(env, messageQueueObj);    //创建NativeInputEventReceiver对象【见小节3.4】    sp<NativeInputEventReceiver> receiver = new NativeInputEventReceiver(env,            receiverWeak, inputChannel, messageQueue);    //【见小节3.5】    status_t status = receiver->initialize();    ...    receiver->incStrong(gInputEventReceiverClassInfo.clazz);     return reinterpret_cast<jlong>(receiver.get());}

3.4 NativeInputEventReceiver

[-> android_view_InputEventReceiver.cpp]

class NativeInputEventReceiver : public LooperCallback {    InputConsumer mInputConsumer;    sp<MessageQueue> mMessageQueue;    int mFdEvents;    bool mBatchedInputEventPending;    ...        NativeInputEventReceiver::NativeInputEventReceiver(JNIEnv* env,            jobject receiverWeak, const sp<InputChannel>& inputChannel,            const sp<MessageQueue>& messageQueue) :            mReceiverWeakGlobal(env->NewGlobalRef(receiverWeak)),            //【见3.4.1】            mInputConsumer(inputChannel), mMessageQueue(messageQueue),            mBatchedInputEventPending(false), mFdEvents(0) {                }}

3.4.1 InputConsumer

[-> InputTransport.cpp]

InputConsumer::InputConsumer(const sp<InputChannel>& channel) :        mResampleTouch(isTouchResamplingEnabled()),        mChannel(channel), mMsgDeferred(false) {}

此处inputChannel是指socket客户端。

3.5 initialize

[-> android_view_InputEventReceiver.cpp]

status_t NativeInputEventReceiver::initialize() {    setFdEvents(ALOOPER_EVENT_INPUT);  //【见小节3.6】    return OK;}

3.6 setFdEvents

[-> android_view_InputEventReceiver.cpp]

void NativeInputEventReceiver::setFdEvents(int events) {  if (mFdEvents != events) {      mFdEvents = events;      int fd = mInputConsumer.getChannel()->getFd();      if (events) {          //将socket客户端的fd添加到主线程的消息池【见小节3.6.1】          mMessageQueue->getLooper()->addFd(fd, 0, events, this, NULL);      } else {          mMessageQueue->getLooper()->removeFd(fd);      }  }}    

3.6.1 Looper.addFd

[-> system/core/libutils/Looper.cpp]

int Looper::addFd(int fd, int ident, int events, const sp<LooperCallback>& callback, void* data) {    {        AutoMutex _l(mLock);        Request request;        request.fd = fd;        request.ident = ident;        request.events = events;        request.seq = mNextRequestSeq++;        request.callback = callback; //是指ativeInputEventReceiver        request.data = data;        if (mNextRequestSeq == -1) mNextRequestSeq = 0;                struct epoll_event eventItem;        request.initEventItem(&eventItem);        ssize_t requestIndex = mRequests.indexOfKey(fd);        if (requestIndex < 0) {            //通过epoll监听fd            int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, fd, & eventItem);            ...            mRequests.add(fd, request); //该fd的request加入到mRequests队列        } else {            int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_MOD, fd, & eventItem);            ...            mRequests.replaceValueAt(requestIndex, request);        }    }     return 1;}

此处的Looper便是UI主线程的Looper，将socket客户端的fd添加到UI线程的Looper来监听，回调方法为NativeInputEventReceiver。

四. 总结

首先，通过openInputChannelPair来创建socket pair，作为InputChannel:

• socket服务端保存到system_server中的WindowState的mInputChannel；
• socket客户端通过binder传回到远程进程的UI主线程ViewRootImpl的mInputChannel；

紧接着，完成了两个线程的epoll监听工作：

• [小节2.8]IMS.registerInputChannel(): “InputDispatcher”线程监听socket服务端，收到消息后回调InputDispatcher.handleReceiveCallback()；
• [小节3.6]setFdEvents(): UI主线程监听socket客户端，收到消息后回调NativeInputEventReceiver.handleEvent().

有了这些“InputDispatcher”和“UI”主线程便可以进行跨进程通信与交互。