Android系统--事件读取及分发

               

1. 简介

      WindowManagerService分发事件是通过它的InputManager来完成的。

      在初始化时，各部分状态如下：

      • InputManager.InputReader：正在睡眠等待事件的发生

      • InputManager.InputDispatcher：正在等待InputReader从睡眠中醒过来并且唤醒它

      • Activity应用程序：正在消息循环中等待InputDispatcher把它唤醒

      初始化之后，如果有事件发生，其调用流程见下面的内容。

2. 事件分发流程

2.1 Server端

   • InputReader
  1) InputReader.pollOnce (InputReader.cpp)
     被通知是否有事件可读
  2) EventHub.getEvent (EventHub.cpp)
     读取真正的事件
  3) InputReader.process (InputReader.cpp)
  4) InputReader.consumeEvent (InputReader.cpp)
  5) InputDevice.process (InputReader.cpp)
  6) mapper->process(rawEvent) (下面以键盘为例)
     则真正调用:  KeyboardInputMapper.process (InputReader.cpp)
  7) KeyboardInputMapper.processKey (InputReader.cpp)

  • InputDispatcher
  8) InputDispatcher.notifyKey (InputDispatcher.cpp)
     a) 生成KeyEvent (通过调用event.initialize)
     b) 生成KeyEntry
     c) 调用enqueueInboundEventLocked(newEntry),把KeyEntry加入到InputDispatcher类的mInboundQueue队列中
     d) 根据需要唤醒InputDispatccherThread线程

  9) InputDispatcher.dispatchOnce (InputDispatcher.cpp)
  10) InputDispatcher.dispatchOnceInnerLocked (InputDispatcher.cpp)
      从mInboundQueue队列中取出EventEntry

  11) InputDispatcher.dispatchKeyLocked (InputDispatcher.cpp)
      a) 从当前激活窗口mFocusedWindowHandle中获取InputWindowInfo
      b) 从InputWindowInfo中获取inputChannel、frameLeft、frameTop并保存在mCurrentInputTargets的top InputTarget成员中。后面InputDispatcher就会从mCurrentInputTargets中取出恰当的Activity窗口，然后把键盘事件分发给它
      c) 调用dispatchEventToCurrentInputTargetsLocked(currentTime, entry, false)

  12) InputDispatcher.dispatchEventToCurrentInputTargetsLocked (InputDispatcher.cpp)

 

// InputDispatcher.cppvoid InputDispatcher::dispatchEventToCurrentInputTargetsLocked(nsecs_t currentTime,        EventEntry* eventEntry, bool resumeWithAppendedMotionSample) {    LOG_ASSERT(eventEntry->dispatchInProgress); // should already have been set to true    pokeUserActivityLocked(eventEntry);    for (size_t i = 0; i < mCurrentInputTargets.size(); i++) {        const InputTarget& inputTarget = mCurrentInputTargets.itemAt(i);        ssize_t connectionIndex = getConnectionIndexLocked(inputTarget.inputChannel);        if (connectionIndex >= 0) {            // 获取对应的Connection            sp<Connection> connection = mConnectionsByReceiveFd.valueAt(connectionIndex);            prepareDispatchCycleLocked(currentTime, connection, eventEntry, & inputTarget,                    resumeWithAppendedMotionSample);        } else {        }    }}

 

  13) InputDispatcher.prepareDispatchCycleLocked (InputDispatcher.cpp)

 

  14) InputDispatcher.enqueueDispatchEntriesLocked (InputDispatcher.cpp)
      (1) InputDispatcher::enqueueDispatchEntryLocked (InputDispatcher.cpp)
        a) 生成DispatchEntry
        b) 把dispatchEntry加入connection->outboundQueue
         (connection->outboundQueue.enqueueAtTail(dispatchEntry))
      (2) InputDispatcher::startDispatchCycleLocked(以前队列空才执行)

 

  15) InputDispatcher.startDispatchCycleLocked (InputDispatcher.cpp)
      (1) 从connection->outboundQueue中取出DispatchEntry
      (2) 对于EventEntry::TYPE_KEY，调用connection->inputPublisher.publishKeyEvent
          或 对于EventEntry::TYPE_MOTION，调用connection->inputPublisher.publishMotionEvent

      (3) InputPublisher.publishKeyEvent (InputTransport.cpp)
          它把key event存入ashmem buffer中，即mSharedMessage->key中，
          此ashmem buffer在InputDispatcher.registerInputChannel (connection->initialize)被创建。
     
      (4) 发送dispath信号(即写发送pipe)给Activity应用程序
          connection->inputPublisher.sendDispatchSignal-> InputChannel.sendSignal 

status_t InputPublisher::sendDispatchSignal() {    mWasDispatched = true;    return mChannel->sendSignal(INPUT_SIGNAL_DISPATCH);}

      至此，已经向Activity应用程序接收pipe中写入内容，则Activity应用程序的主线程就被唤醒了，开始处理此事件，即Activity应用程序上场了！

2.2 Client端 (Activity应用程序)

      当应用程序的主线程因为这个InputChannel中的读管道被写端唤醒时，NativeInputQueue的成员函数handleReceiveCallback就会被回调，因此，接下来，应用程序的主线程就会被唤醒，然后执行NativeInputQueue的成员函数handleReceiveCallback。

   • NativeInputQueue
   1) NativeInputQueue::handleReceiveCallback (android_view_InputQueue.cpp)
     详细见容见下面的注释

int NativeInputQueue::handleReceiveCallback(int receiveFd, int events, void* data) {    NativeInputQueue* q = static_cast<NativeInputQueue*>(data);    JNIEnv* env = AndroidRuntime::getJNIEnv();    sp<Connection> connection;    InputEvent* inputEvent;    jobject inputHandlerObjLocal;    jlong finishedToken;    { // acquire lock        AutoMutex _l(q->mLock);        // 根据receiveFd获取 connectionIndex        ssize_t connectionIndex = q->mConnectionsByReceiveFd.indexOfKey(receiveFd);         ...        // 根据connectionIndex获取NativeInputQueue.Connection        connection = q->mConnectionsByReceiveFd.valueAt(connectionIndex);        ...        // 从管道读取数据并检查是否与发送方写的一致        status_t status = connection->inputConsumer.receiveDispatchSignal();         ...        // 获取NativeInputQueue.Connection中的InputConsumer对象,它与Server端的InputPublisher对应        // InputConsumer::consume (InputTransport.cpp), 负责把事件读出来(MotionEvent或KeyEvent)并生成inputEventObj        status = connection->inputConsumer.consume(& connection->inputEventFactory, & inputEvent);        ...               connection->messageInProgress = true;        connection->messageSeqNum += 1;        finishedToken = generateFinishedToken(receiveFd, connection->id, connection->messageSeqNum);         // 获取inputHandlerObjLocal对象        // 在NativeInputQueue.registerInputChannel中Java传入，并保存在Connection中        inputHandlerObjLocal = env->NewLocalRef(connection->inputHandlerObjGlobal);    } // release lock    int32_t inputEventType = inputEvent->getType();    jobject inputEventObj;    jmethodID dispatchMethodId;    switch (inputEventType) {    case AINPUT_EVENT_TYPE_KEY:        // 生成inputEventObj        inputEventObj = android_view_KeyEvent_fromNative(env,                static_cast<KeyEvent*>(inputEvent));                // 以指定inputHandlerObjLocal调用InputQueue.dispatchKeyEvent来处理此事件         dispatchMethodId = gInputQueueClassInfo.dispatchKeyEvent;        break;    case AINPUT_EVENT_TYPE_MOTION:        inputEventObj = android_view_MotionEvent_obtainAsCopy(env,                static_cast<MotionEvent*>(inputEvent));        dispatchMethodId = gInputQueueClassInfo.dispatchMotionEvent;        break;    default:        assert(false); // InputConsumer should prevent this from ever happening        inputEventObj = NULL;    }    if (! inputEventObj) {        LOGW("channel '%s' ~ Failed to obtain DVM event object.",                connection->getInputChannelName());        env->DeleteLocalRef(inputHandlerObjLocal);        q->finished(env, finishedToken, false, false);        return 1;    }        // 通知Java层的InputQueue来处理这个事件    env->CallStaticVoidMethod(gInputQueueClassInfo.clazz,            dispatchMethodId, inputHandlerObjLocal, inputEventObj,            jlong(finishedToken));    if (env->ExceptionCheck()) {        LOGE("An exception occurred while invoking the input handler for an event.");        LOGE_EX(env);        env->ExceptionClear();        q->finished(env, finishedToken, false, true /*ignoreSpuriousFinish*/);    }    env->DeleteLocalRef(inputEventObj);    env->DeleteLocalRef(inputHandlerObjLocal);    return 1;}

   • NativeInputQueue (下面以处理KeyEvent来讲)
   2) InputQueue.dispatchKeyEvent (InputQueue.java)  

 

    private static void dispatchKeyEvent(InputHandler inputHandler,            KeyEvent event, long finishedToken) {        FinishedCallback finishedCallback = FinishedCallback.obtain(finishedToken);        // inputHandler是调用InputQueue.registerInputChannel时传进来的        // 在ViewRootImpl.setView中调用        // InputQueue.registerInputChannel(mInputChannel, mInputHandler,        //                        Looper.myQueue())        inputHandler.handleKey(event, finishedCallback);    }

         mInputHandler的定义如下：

    private final InputHandler mInputHandler = new InputHandler() {        public void handleKey(KeyEvent event, InputQueue.FinishedCallback finishedCallback) {            startInputEvent(finishedCallback);            dispatchKey(event, true);        }        public void handleMotion(MotionEvent event, InputQueue.FinishedCallback finishedCallback) {            startInputEvent(finishedCallback);            dispatchMotion(event, true);        }    };

 

   3) mInputHandler.handleKey (ViewRootImpl.java)
   4) ViewRootImpl.dispatchKey (ViewRootImpl.java)
      把KeyEvent封装成Message
   5) ViewRootImpl.enqueueInputEvent
      把Message转换为InputEventMessage消息，然后放于mPendingInputEvents链表尾。
      ViewRootImpl不直接处理这个事件，而是把它作为一个消息(DISPATCH_KEY)放到消息队列中去处理，这个消息最后由ViewRootImpl类的deliverKeyEvent成员函数来处理
   6) 在handleMessage中调用deliverKeyEvent

   7) ViewRootImpl.deliverKeyEvent (ViewRootImpl.java)

    private void deliverKeyEvent(KeyEvent event, boolean sendDone) {        if (ViewDebug.DEBUG_LATENCY) {            mInputEventDeliverTimeNanos = System.nanoTime();        }        if (mInputEventConsistencyVerifier != null) {            mInputEventConsistencyVerifier.onKeyEvent(event, 0);        }        // If there is no view, then the event will not be handled.        if (mView == null || !mAdded) {            finishKeyEvent(event, sendDone, false);            return;        }           // Perform predispatching before the IME.        if (mView.dispatchKeyEventPreIme(event)) {            finishKeyEvent(event, sendDone, true);            return;        }        // InputMethodManager处理完这个键盘事件后，再回调用这里的        // mInputMethodCallback对象的finishedEvent成员函数来把键盘        // 事件分发给当前激活的Activity窗口处理。当然，在把这个键盘事件        // 分发给InputMethodManager处理之前，ViewRoot也会先把这个键盘事        // 件分发给当前激活的Activity窗口的dispatchKeyEventPreIme成员函数处理。         // Dispatch to the IME before propagating down the view hierarchy.        // The IME will eventually call back into handleFinishedEvent.        if (mLastWasImTarget) {            InputMethodManager imm = InputMethodManager.peekInstance();            if (imm != null) {                int seq = enqueuePendingEvent(event, sendDone);                imm.dispatchKeyEvent(mView.getContext(), seq, event, mInputMethodCallback);                return;            }        }        // Not dispatching to IME, continue with post IME actions.        deliverKeyEventPostIme(event, sendDone);    }     

    8) InputMethodCallack.finishedEvent (ViewRootImpl.java)
    9) ViewRootImpl.dispatchFinishedEvent (ViewRootImpl.java)
       发送FINISHED_EVENT到队列
    10) ViewRootImpl.dispatchFinishedEvent (ViewRootImpl.java)
        如果InputMethodManager没有处理这个键盘事件，那么ViewRoot就会把
        这个键盘事件分发给当前激活的Activity窗口来处理。
    11) ViewRootImpl.deliverKeyEventPostIme (ViewRootImpl.java)
    12) mView.dispatchKeyEvent(event) (ViewRootImpl.java)
        把事件分发给view hierarchy, mView为DecorView
    13) DecorView.dispatchKeyEvent (PhoneWindow.java)

          public boolean dispatchKeyEvent(KeyEvent event) {            final int keyCode = event.getKeyCode();            final int action = event.getAction();            final boolean isDown = action == KeyEvent.ACTION_DOWN;            if (!isDestroyed()) {                // 返回当前应用程序的激活的Activity窗口的Window.Callback接口,一般不为NULL                // 因此，这个函数会调用Activity类的dispatchKeyEvent来处理这个键盘事件                final Callback cb = getCallback();                final boolean handled = cb != null && mFeatureId < 0 ? cb.dispatchKeyEvent(event)                        : super.dispatchKeyEvent(event);                if (handled) {                    return true;                }            }            return isDown ? PhoneWindow.this.onKeyDown(mFeatureId, event.getKeyCode(), event)                    : PhoneWindow.this.onKeyUp(mFeatureId, event.getKeyCode(), event);        }   

    14) Activity.dispatchKeyEvent (Activity.java)

  public boolean dispatchKeyEvent(KeyEvent event) {        onUserInteraction();        Window win = getWindow();        if (win.superDispatchKeyEvent(event)) {            return true;        }        View decor = mDecor;        if (decor == null) decor = win.getDecorView();        return event.dispatch(this, decor != null                ? decor.getKeyDispatcherState() : null, this);    }

    Activity不是直接处理这个键盘事件，而是通过KeyEvent的dispatch转发一下。
    注意，KeyEvent的成中函数dispatch的第一个参数的类型是KeyEvent.Callback，而Activity实现了这个接口，因此，这里可以传this引用过去。

   15) KeyEvent.dispatch (KeyEvent.java)
      根据一个键是按下(ACTION_DOWN)、还是松开(ACTION_UP) 或者是一个相同的键被多次按下和松开(ACTION_MULTIPLE)等不同事件类型来分别调用(receiver为Activity)Activity的onKeyDown、onKeyLongPres、sonKeyUp和onKeyMultiple函数了。
      执行完此函数，然后再一层一层向上返回。

 

 

 

 

 

 

           

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