ADROID 2.1 架构解析 7 键盘

7 键盘

系统在KeyInputQueue服务里创建了一个线程，在这个线程里不断读取输入事件，然后对这个事件进行处理。

7.1 按键输入队列服务

按键输入事件有多种方式，如：键盘敲击、触摸屏触击、鼠标点击及多点触摸，主要是按下和放开的事件。

7.1.1 输入事件的数据结构

文件：frameworks/base/core/java/android/view/RawInputEvent.java

public class RawInputEvent {

    // Event class as defined by EventHub.

    ...

    public int deviceId;

    public int type;

    public int scancode;

    public int keycode;

    public int flags;

    public int value;

    public long when;

}

7.1.2 输入事件服务

文件：frameworks/base/services/java/com/android/server/KeyInputQueue.java

7.1.2.1 获取事件

Thread mThread = new Thread("InputDeviceReader") {

        public void run() {

            if (DEBUG) Log.v(TAG, "InputDeviceReader.run()");

            android.os.Process.setThreadPriority(

                    android.os.Process.THREAD_PRIORITY_URGENT_DISPLAY);

        

            RawInputEvent ev = new RawInputEvent();

            while (true) {

                try {                  

                                   ...

                    // block, doesn't release the monitor

                    readEvent(ev);

                                   ...

调用readEvent，将输入事件读取到ev类，即RawInputEvent的变量里，readEvent对应jni的android_server_KeyInputQueue_readEvent

7.1.2.2 处理键盘事件

              ...

              public static KeyEvent newKeyEvent(InputDevice device, long downTime,

            long eventTime, boolean down, int keycode, int repeatCount,

            int scancode, int flags) {

        return new KeyEvent(

                downTime, eventTime,

                down ? KeyEvent.ACTION_DOWN : KeyEvent.ACTION_UP,

                keycode, repeatCount,

                device != null ? device.mMetaKeysState : 0,

                device != null ? device.id : -1, scancode,

                flags | KeyEvent.FLAG_FROM_SYSTEM);

}

Thread mThread = new Thread("InputDeviceReader") {

        public void run() {

            if (DEBUG) Log.v(TAG, "InputDeviceReader.run()");

            android.os.Process.setThreadPriority(

                    android.os.Process.THREAD_PRIORITY_URGENT_DISPLAY);

           

            RawInputEvent ev = new RawInputEvent();

            while (true) {

                try {

                    InputDevice di;

 

                    // block, doesn't release the monitor

                    readEvent(ev);

              ...

 

              final int scancode = ev.scancode;

              if (type == RawInputEvent.EV_KEY &&

                                (classes&RawInputEvent.CLASS_KEYBOARD) != 0 &&

                                (scancode < RawInputEvent.BTN_FIRST ||

                                        scancode > RawInputEvent.BTN_LAST)) {

                            boolean down;

                            if (ev.value != 0) {

                                down = true;

                                di.mKeyDownTime = curTime;

                            } else {

                                down = false;

                            }

                            int keycode = rotateKeyCodeLocked(ev.keycode);

                            addLocked(di, curTimeNano, ev.flags,

                                    RawInputEvent.CLASS_KEYBOARD,

                                    newKeyEvent(di, di.mKeyDownTime, curTime, down,

                                           keycode, 0, scancode,

                                           ((ev.flags & WindowManagerPolicy.FLAG_WOKE_HERE) != 0)

                                            ? KeyEvent.FLAG_WOKE_HERE : 0));

                           

                        }

处理键盘事件，并将该事件加入事件队列。

7.2硬件调用

文件：frameworks/base/services/jni/com_android_server_KeyInputQueue.cpp

int register_android_server_KeyInputQueue(JNIEnv* env)

{

    ...

    jclass inputEvent = env->FindClass("android/view/RawInputEvent");

    gInputOffsets.mDeviceId

        = env->GetFieldID(inputEvent, "deviceId", "I");

    gInputOffsets.mType

        = env->GetFieldID(inputEvent, "type", "I");

    gInputOffsets.mScancode

        = env->GetFieldID(inputEvent, "scancode", "I");

    gInputOffsets.mKeycode

        = env->GetFieldID(inputEvent, "keycode", "I");

    gInputOffsets.mFlags

        = env->GetFieldID(inputEvent, "flags", "I");

    gInputOffsets.mValue

        = env->GetFieldID(inputEvent, "value", "I");

    gInputOffsets.mWhen

        = env->GetFieldID(inputEvent, "when", "J");

    ...

}

获取android/view/RawInputEvent类的变量。

 

static jboolean

android_server_KeyInputQueue_readEvent(JNIEnv* env, jobject clazz,

                                          jobject event)

{

    gLock.lock();

    sp<EventHub> hub = gHub;

    if (hub == NULL) {

        hub = new EventHub;

        gHub = hub;

    }

    gLock.unlock();

 

    int32_t deviceId;

    int32_t type;

    int32_t scancode, keycode;

    uint32_t flags;

    int32_t value;

    nsecs_t when;

    bool res = hub->getEvent(&deviceId, &type, &scancode, &keycode,

            &flags, &value, &when);

 

    env->SetIntField(event, gInputOffsets.mDeviceId, (jint)deviceId);

    env->SetIntField(event, gInputOffsets.mType, (jint)type);

    env->SetIntField(event, gInputOffsets.mScancode, (jint)scancode);

    env->SetIntField(event, gInputOffsets.mKeycode, (jint)keycode);

    env->SetIntField(event, gInputOffsets.mFlags, (jint)flags);

    env->SetIntField(event, gInputOffsets.mValue, value);

    env->SetLongField(event, gInputOffsets.mWhen,

                        (jlong)(nanoseconds_to_milliseconds(when)));

 

    return res;

}

将从eventhub读到的变量存到android/view/RawInputEvent类对应的变量里。

7.3 EventHub库

文件：frameworks/base/libs/ui/EventHub.cpp

7.3.1 读取输入设备状态

static const char *device_path = "/dev/input";

bool EventHub::getEvent(int32_t* outDeviceId, int32_t* outType,

        int32_t* outScancode, int32_t* outKeycode, uint32_t *outFlags,

        int32_t* outValue, nsecs_t* outWhen)

{   

       ...

    if (!mOpened) {

        mError = openPlatformInput() ? NO_ERROR : UNKNOWN_ERROR;

        mOpened = true;

    }

       ...

    while(1) {

 

        pollres = poll(mFDs, mFDCount, -1);

 

        // mFDs[0] is used for inotify, so process regular events starting at mFDs[1]

        for(i = 1; i < mFDCount; i++) {

            if(mFDs[i].revents) {

                LOGV("revents for %d = 0x%08x", i, mFDs[i].revents);

                if(mFDs[i].revents & POLLIN) {

                    res = read(mFDs[i].fd, &iev, sizeof(iev));

                    if (res == sizeof(iev)) {

                        *outDeviceId = mDevices[i]->id;

                        if (*outDeviceId == mFirstKeyboardId) *outDeviceId = 0;

                        *outType = iev.type;

                        *outScancode = iev.code;

                        if (iev.type == EV_KEY) {

                            err = mDevices[i]->layoutMap->map(iev.code, outKeycode, outFlags);

                            if (err != 0) {

                                *outKeycode = 0;

                                *outFlags = 0;

                            }

                        } else {

                            *outKeycode = iev.code;

                        }

                        *outValue = iev.value;

                        *outWhen = s2ns(iev.time.tv_sec) + us2ns(iev.time.tv_usec);

                        return true;

                    } else {

                        if (res<0) {

                            LOGW("could not get event (errno=%d)", errno);

                        } else {

                            LOGE("could not get event (wrong size: %d)", res);

                        }

                        continue;

                    }

                }

            }

        }

       

        // read_notify() will modify mFDs and mFDCount, so this must be done after

        // processing all other events.

        if(mFDs[0].revents & POLLIN) {

            read_notify(mFDs[0].fd);

        }

    }

}

openPlatformInput() 打开/dev/input/ 目录下的所有输入设备文件。

打开设备后，不断轮循所有设备，直到读取有POLLIN事件产生的设备的状态。

7.3.2 导入键盘配置文件

int EventHub::open_device(const char *deviceName)

{

       ...

       if(ioctl(fd, EVIOCGNAME(sizeof(name) - 1), &name) < 1) {

        //fprintf(stderr, "could not get device name for %s, %s/n", deviceName, strerror(errno));

        name[0] = '/0';

    }

       ...

if ((device->classes&CLASS_KEYBOARD) != 0) {

        char tmpfn[sizeof(name)];

        char keylayoutFilename[300];

 

        // a more descriptive name

        device->name = name;

 

        // replace all the spaces with underscores

        strcpy(tmpfn, name);

        for (char *p = strchr(tmpfn, ' '); p && *p; p = strchr(tmpfn, ' '))

            *p = '_';

 

        // find the .kl file we need for this device

        const char* root = getenv("ANDROID_ROOT");

        snprintf(keylayoutFilename, sizeof(keylayoutFilename),

                 "%s/usr/keylayout/%s.kl", root, tmpfn);

        bool defaultKeymap = false;

        if (access(keylayoutFilename, R_OK)) {

            snprintf(keylayoutFilename, sizeof(keylayoutFilename),

                     "%s/usr/keylayout/%s", root, "qwerty.kl");

            defaultKeymap = true;

        }

        device->layoutMap->load(keylayoutFilename);

 

        // tell the world about the devname (the descriptive name)

        int32_t publicID;

        if (!mHaveFirstKeyboard && !defaultKeymap) {

            publicID = 0;

            // the built-in keyboard has a well-known device ID of 0,

            // this device better not go away.

            mHaveFirstKeyboard = true;

            mFirstKeyboardId = device->id;

        } else {

            publicID = device->id;

            // ensure mFirstKeyboardId is set to -something-.

            if (mFirstKeyboardId == 0) {

                mFirstKeyboardId = device->id;

            }

        }

        char propName[100];

        sprintf(propName, "hw.keyboards.%u.devname", publicID);

        property_set(propName, name);

 

        // 'Q' key support = cheap test of whether this is an alpha-capable kbd

        if (hasKeycode(device, kKeyCodeQ)) {

            device->classes |= CLASS_ALPHAKEY;

        }

       

        // See if this has a DPAD.

        if (hasKeycode(device, kKeyCodeDpadUp) &&

                hasKeycode(device, kKeyCodeDpadDown) &&

                hasKeycode(device, kKeyCodeDpadLeft) &&

                hasKeycode(device, kKeyCodeDpadRight) &&

                hasKeycode(device, kKeyCodeDpadCenter)) {

            device->classes |= CLASS_DPAD;

        }

       

        LOGI("New keyboard: publicID=%d device->id=0x%x devname='%s' propName='%s' keylayout='%s'/n",

                publicID, device->id, name, propName, keylayoutFilename);

    }

       ...

}

由以上代码可知，会优先加载/system/usr/keylayout/输入设备名称.kl

如: /sys/class/input/input1/name = keypad，则会加载/system/usr/keylayout/keypad.kl，如果该文件不存在，则加载默认文件/system/usr/keylayout/qwerty.kl，该文件的原型在：sdk/emulator/keymaps/qwerty.kl ，eclair以前的版本都是放在development/ emulator/keymaps/qwerty.kl

7.3.3 按键映射

如7.3.2所示代码，先加载配置文件：

device->layoutMap->load(keylayoutFilename);

如7.3.1所示代码，再将读取到的按键码进行转换：

err = mDevices[i]->layoutMap->map(iev.code, outKeycode, outFlags);

文件：frameworks/base/libs/ui/KeyLayoutMap.cpp

status_t

KeyLayoutMap::load(const char* filename)

{

int fd = open(filename, O_RDONLY);

...

while (true) {

        String8 token = next_token(&p, &line);

        if (*p == '/0') {

            break;

        }

        switch (state)

        {

            case BEGIN:

                if (token == "key") {

                    state = SCANCODE;

                } else {

                    LOGE("%s:%d: expected key, got '%s'/n", filename, line,

                            token.string());

                    err = BAD_VALUE;

                    goto done;

                }

                break;

            case SCANCODE:

                scancode = strtol(token.string(), &end, 0);

                if (*end != '/0') {

                    LOGE("%s:%d: expected scancode (a number), got '%s'/n",

                            filename, line, token.string());

                    goto done;

                }

                //LOGI("%s:%d: got scancode %d/n", filename, line, scancode );

                state = KEYCODE;

                break;

            case KEYCODE:

                keycode = token_to_value(token.string(), KEYCODES);

                //LOGI("%s:%d: got keycode %d for %s/n", filename, line, keycode, token.string() );

                if (keycode == 0) {

                    LOGE("%s:%d: expected keycode, got '%s'/n",

                            filename, line, token.string());

                    goto done;

                }

                state = FLAG;

                break;

            case FLAG:

                if (token == "key") {

                    if (scancode != -1) {

                        //LOGI("got key decl scancode=%d keycode=%d"

                        //       " flags=0x%08x/n", scancode, keycode, flags);

                        Key k = { keycode, flags };

                        m_keys.add(scancode, k);

                        state = SCANCODE;

                        scancode = -1;

                        keycode = -1;

                        flags = 0;

                        break;

                    }

                }

                tmp = token_to_value(token.string(), FLAGS);

                //LOGI("%s:%d: got flags %x for %s/n", filename, line, tmp, token.string() );

                if (tmp == 0) {

                    LOGE("%s:%d: expected flag, got '%s'/n",

                            filename, line, token.string());

                    goto done;

                }

                flags |= tmp;

                break;

        }

    }

...

}

由以上代码可知，是以如下方式对配置文件进行解析的：

BEGIN: 如果第一个关键字是key，则转入SCANCODE，否则退出。

SCANCODE: 将第二个关键字转为数字，即扫描码scancode，转向KEYCODE。

KEYCODE: 将第三个关键字与KEYCODES列表配对，找出关键码keycode，转向FLAG。

FLAG:如果第四个关键字是key，则保存刚扫描的键码，然后转向SCANCODE，否则将该关键字与FLAGS列表配对，找出flags值，然后转向BEGIN。

 

注：KEYCODES列表和FLAGS列表的定义在：

frameworks/base/include/ui/KeycodeLabels.h

 

status_t

KeyLayoutMap::map(int32_t scancode, int32_t *keycode, uint32_t *flags) const

{

    if (m_status != NO_ERROR) {

        return m_status;

    }

 

    ssize_t index = m_keys.indexOfKey(scancode);

    if (index < 0) {

        //LOGW("couldn't map scancode=%d/n", scancode);

        return NAME_NOT_FOUND;

    }

 

    const Key& k = m_keys.valueAt(index);

 

    *keycode = k.keycode;

    *flags = k.flags;

 

    //LOGD("mapped scancode=%d to keycode=%d flags=0x%08x/n", scancode,

    //        keycode, flags);

 

    return NO_ERROR;

}

Map的功能是根据scancode，找到对应的keycode.

 

qwerty.kl 的部分配置：

#  scancode    keycode      flags

key 399   GRAVE

key 2     1

key 3     2

key 4     3

key 5     4

key 6     5

key 7     6

key 8     7

key 9     8

key 10    9

key 11    0

key 158   BACK              WAKE_DROPPED

key 230   SOFT_RIGHT        WAKE

key 60    SOFT_RIGHT        WAKE

 

7.4 字符映射

7.4.1 加载字符配置表

文件：frameworks/base/core/java/android/view/KeyCharacterMap.java
public static KeyCharacterMap load(int keyboard)

{

       ...

            result = new KeyCharacterMap(keyboard);

              ...

     }

private KeyCharacterMap(int keyboardDevice)

    {

        mKeyboardDevice = keyboardDevice;

        mPointer = ctor_native(keyboardDevice);

    }

ctor_native 原型如下：

文件：frameworks/base/core/jni/android_text_KeyCharacterMap.cpp

static JNINativeMethod g_methods[] = {

    /* name, signature, funcPtr */

{ "ctor_native",             "(I)I",    (void*)ctor },

...

};

static jint

ctor(JNIEnv *env, jobject clazz, jint id)

{

    return reinterpret_cast<int>(KeyCharacterMap::load(id));

}

KeyCharacterMap::load原型如下：

文件：frameworks/base/libs/ui/KeyCharacterMap.cpp

KeyCharacterMap*

KeyCharacterMap::load(int id)

{

    KeyCharacterMap* rv = NULL;

    char path[PATH_MAX];

    char propName[100];

    char dev[PROPERTY_VALUE_MAX];

    char tmpfn[PROPERTY_VALUE_MAX];

    int err;

    const char* root = getenv("ANDROID_ROOT");

 

    sprintf(propName, "hw.keyboards.%u.devname", id);

    err = property_get(propName, dev, "");

    if (err > 0) {

        // replace all the spaces with underscores

        strcpy(tmpfn, dev);

        for (char *p = strchr(tmpfn, ' '); p && *p; p = strchr(tmpfn, ' '))

            *p = '_';

        snprintf(path, sizeof(path), "%s/usr/keychars/%s.kcm.bin", root, tmpfn);

        //LOGD("load: dev='%s' path='%s'/n", dev, path);

        rv = try_file(path);

        if (rv != NULL) {

            return rv;

        }

        LOGW("Error loading keycharmap file '%s'. %s='%s'", path, propName, dev);

    } else {

        LOGW("No keyboard for id %d", id);

    }

 

    snprintf(path, sizeof(path), "%s/usr/keychars/qwerty.kcm.bin", root);

    rv = try_file(path);

    if (rv == NULL) {

        LOGE("Can't find any keycharmaps (also tried %s)", path);

        return NULL;

    }

    LOGW("Using default keymap: %s", path);

 

    return rv;

}

以上所提及代码要实现的功能是：先查看hw.keyboards.%u.devname的属性，若存在则打开/system/usr/keychars/%s.kcm.bin文件，否则打开默认文件：/system/usr/keychars/qwerty.kcm.bin

 

文件：frameworks/base/libs/ui/EventHub.cpp

参考<<7.3.2 导入键盘配置文件>>里的：

char propName[100];

        sprintf(propName, "hw.keyboards.%u.devname", publicID);

        property_set(propName, name);

在代码里设置了KeyCharacterMap::load中hw.keyboards.%u.devname所需要的值，即设备名称，如: /sys/class/input/input1/name = keypad，则会加载/system/usr/keychars/keypad.kcm.bin

 

例：

/sys/class/input/input1/name = keypad

则要打开的文件路径是：

/system/usr/keylayout/keypad.kl

/system/usr/keychars/keypad.kcm.bin

若以上文件不存在，则使用默认文件：

/system/usr/keylayout/qwerty.kl

/system/usr/keychars/qwerty.kcm.bin

7.4.2字符映射

文件：frameworks/base/core/java/android/view/KeyCharacterMap.java

public char getMatch(int keyCode, char[] chars)

    {

        return getMatch(keyCode, chars, 0);

    }

    public char getMatch(int keyCode, char[] chars, int modifiers)

    {

        if (chars == null) {

            // catch it here instead of in native

            throw new NullPointerException();

        }

        return getMatch_native(mPointer, keyCode, chars, modifiers);

}

getMatch_native 原型如下：

文件：frameworks/base/core/jni/android_text_KeyCharacterMap.cpp

static JNINativeMethod g_methods[] = {

    /* name, signature, funcPtr */

{ "getMatch_native",        "(II[CI)C", (void*)getMatch },

...

};

static jchar

getMatch(JNIEnv *env, jobject clazz, jint ptr, jint keycode, jcharArray chars, jint modifiers)

{

    jchar rv;

    jchar* ch = env->GetCharArrayElements(chars, NULL);

    jsize chsize = env->GetArrayLength(chars);

 

    rv = reinterpret_cast<KeyCharacterMap*>(ptr)->getMatch(keycode, ch, chsize, modifiers);

 

    env->ReleaseCharArrayElements(chars, ch, JNI_ABORT);

    return rv;

}

getMatch的原型如下：

文件：frameworks/base/libs/ui/KeyCharacterMap.cpp

unsigned short

KeyCharacterMap::getMatch(int keycode, const unsigned short* chars,

                          int charsize, uint32_t modifiers)

{

    Key* k = find_key(keycode);

    modifiers &= 3; // ignore the SYM key because we don't have keymap entries for it

    if (k != NULL) {

        const uint16_t* data = k->data;

        for (int j=0; j<charsize; j++) {

            uint16_t c = chars[j];

            for (int i=0; i<(META_MASK + 1); i++) {

                if ((modifiers == 0) || ((modifiers & i) != 0)) {

                    if (c == data[i]) {

                        return c;

                    }

                }

            }

        }

    }

    return 0;

}

 qwerty.kcm的部分配置：

[type=QWERTY]                                          

                                                       

# keycode       display number  base    caps    fn      caps_fn

                                                       

A               'A'     '2'     'a'     'A'     '#'     0x00

B               'B'     '2'     'b'     'B'     '<'     0x00

C               'C'     '2'     'c'     'C'     '9'     0x00E7

D               'D'     '3'     'd'     'D'     '5'     0x00

E               'E'     '3'     'e'     'E'     '2'     0x0301

F               'F'     '3'     'f'     'F'     '6'     0x00A5

G               'G'     '4'     'g'     'G'     '-'     '_'

H               'H'     '4'     'h'     'H'     '['     '{'

I               'I'     '4'     'i'     'I'     '$'     0x0302

J               'J'     '5'     'j'     'J'     ']'     '}'

找到keyCode对应的所有字符，然后再根据modifiers选择对应的字符

7.5 流程总结

当有按键响应时，内核传给ANDROID的是scancode，ANDROID将scancode经配置表(如qwerty.kl)找到keycode标识符，然后由内部表KEYCODES列表找到keycode的数字值，再由keycode的数字值经字符配置表（如qwerty.kcm）找到对应的字符值。

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