Andorid N 最近任务管理器流程详解（五）

5、其他

这章节主要会讲mRecentTasks赋值的地方，截图的时机，一些重点方法等

5.1 mRecentTasks赋值

分别会在startActivity的过程中和重新resume时对mRecentTasks赋值，另外ActivityStack和AMS两者中的mRecentTasks是同一个，具体可以看源码分析

5.1.1 startActivity

其中startActivity这种情况的代码是：
文件：ActivityStackSupervisor.java

    final boolean realStartActivityLocked(ActivityRecord r, ProcessRecord app,              boolean andResume, boolean checkConfig) throws RemoteException {          ...          if (andResume) {              // 见5.1.2            stack.minimalResumeActivityLocked(r);          }          ...      }  

5.1.2 minimalResumeActivityLocked

文件：ActivityStack.java

    void minimalResumeActivityLocked(ActivityRecord r) {        r.state = ActivityState.RESUMED;        if (DEBUG_STATES) Slog.v(TAG_STATES, "Moving to RESUMED: " + r + " (starting new instance)"                + " callers=" + Debug.getCallers(5));        mResumedActivity = r;        r.task.touchActiveTime();        // 赋值的代码        mRecentTasks.addLocked(r.task);        completeResumeLocked(r);        mStackSupervisor.checkReadyForSleepLocked();        setLaunchTime(r);    }

将TaskRecord对象加入到mRecentTasks对象中

5.1.2 重新resume

文件：ActivityStack.java

private boolean resumeTopActivityInnerLocked(ActivityRecord prev, ActivityOptions options) {      ...      // 给mRecentTasks赋值    mRecentTasks.addLocked(next.task);      ...  }  

5.2 截图的时机

截图的时机是在Activity onPause时完成的，首先找到onPause的代码：
文件：ActivityStack.java

    private void completePauseLocked(boolean resumeNext, ActivityRecord resuming) {        ......        // 见5.2.1         mStackSupervisor.ensureActivitiesVisibleLocked(resuming, 0, !PRESERVE_WINDOWS);    }

5.2.1 ensureActivitiesVisibleLocked

文件：ActivityStackSupervisor.java

    void ensureActivitiesVisibleLocked(ActivityRecord starting, int configChanges,            boolean preserveWindows) {        // First the front stacks. In case any are not fullscreen and are in front of home.        for (int displayNdx = mActivityDisplays.size() - 1; displayNdx >= 0; --displayNdx) {            final ArrayList<ActivityStack> stacks = mActivityDisplays.valueAt(displayNdx).mStacks;            final int topStackNdx = stacks.size() - 1;            for (int stackNdx = topStackNdx; stackNdx >= 0; --stackNdx) {                final ActivityStack stack = stacks.get(stackNdx);                // 见5.2.2                stack.ensureActivitiesVisibleLocked(starting, configChanges, preserveWindows);            }        }    }

继续调用ActivityStack的ensureActivitiesVisibleLocked

5.2.2 ensureActivitiesVisibleLocked

文件：ActivityStack.java

    final void ensureActivitiesVisibleLocked(ActivityRecord starting, int configChanges,              boolean preserveWindows) {          ...          makeInvisible(r, visibleBehind);          ...      }  

接着调用makeInvisible

    private void makeInvisible(ActivityRecord r, ActivityRecord visibleBehind) {            ......                        // 见5.2.3            setVisible(r, false);            ......    }

5.2.3 setVisible

文件：ActivityStack.java

    private void setVisible(ActivityRecord r, boolean visible) {        r.visible = visible;        if (!visible && r.mUpdateTaskThumbnailWhenHidden) {            // 更新TaskThumbnail,调用screenshotActivitiesLocked，才是真正截图的地方            r.updateThumbnailLocked(r.task.stack.screenshotActivitiesLocked(r), null);            r.mUpdateTaskThumbnailWhenHidden = false;        }        mWindowManager.setAppVisibility(r.appToken, visible);        final ArrayList<ActivityContainer> containers = r.mChildContainers;        for (int containerNdx = containers.size() - 1; containerNdx >= 0; --containerNdx) {            ActivityContainer container = containers.get(containerNdx);            container.setVisible(visible);        }        mStackSupervisor.mAppVisibilitiesChangedSinceLastPause = true;    }

看到screenshotActivitiesLocked你应该就会感到很熟悉，之前讲获取缩略图时讲到过，这个是截图的方法，所以setVisible才是真正截图的地方

截图之后，会同过saveImage保存起来，你应该会有映像，在缩略图的获取那个章节中，setLastThumbnailLocked方法调用了该方法，接下来我们来看看saveImage方法

5.2.4 saveImage

文件：RecentTasks.java

    void saveImage(Bitmap image, String path) {        // 见5.2.5 保存缩略图        mTaskPersister.saveImage(image, path);    }

5.2.5 保存缩略图

文件：TaskPersister.java

    void saveImage(Bitmap image, String filePath) {        synchronized (this) {            int queueNdx;            for (queueNdx = mWriteQueue.size() - 1; queueNdx >= 0; --queueNdx) {                final WriteQueueItem item = mWriteQueue.get(queueNdx);                if (item instanceof ImageWriteQueueItem) {                    ImageWriteQueueItem imageWriteQueueItem = (ImageWriteQueueItem) item;                    if (imageWriteQueueItem.mFilePath.equals(filePath)) {                        // replace the Bitmap with the new one.                        imageWriteQueueItem.mImage = image;                        break;                    }                }            }            if (queueNdx < 0) {                mWriteQueue.add(new ImageWriteQueueItem(filePath, image));            }            if (mWriteQueue.size() > MAX_WRITE_QUEUE_LENGTH) {                mNextWriteTime = FLUSH_QUEUE;            } else if (mNextWriteTime == 0) {                mNextWriteTime = SystemClock.uptimeMillis() + PRE_TASK_DELAY_MS;            }            // 可以看到保存的路径***            if (DEBUG) Slog.d(TAG, "saveImage: filePath=" + filePath + " now=" +                    SystemClock.uptimeMillis() + " mNextWriteTime=" +                    mNextWriteTime + " Callers=" + Debug.getCallers(4));            notifyAll();        }        yieldIfQueueTooDeep();    }

看filePath可以的得知路径为：/data/system_ce/0/recent_images

5.3 布局

• recent.xml –> 最近任务管理器的布局
  
  • RecentsView –> 显示最近任务列表的
    
    • private TaskStackView mTaskStackView –> 记录了所有的TaskView；每一个TaskView都代表了一个recent app，也就是一个任务；
      
      • TaskView中onLongClick是处理托动的方法，里面
        EventBus.getDefault().register(this, RecentsActivity.EVENT_BUS_PRIORITY + 1);
EventBus.getDefault().send(new DragStartEvent(mTask, this, mDownTouchPos));
        是处理事件的开始

5.4 事件处理

• 一般事件的发出方为：TaskView和TaskStackView
• 事件定义的路径为：frameworks/base/packages/SystemUI/src/com/android/systemui/recents/events

5.5 时序图

暂无