Android输入输出机制之前因后果以前生后世

 

先讲一下基本通常的输入处理方式的知识。通常的输入输出采用生产者，消费者模式，并构造队列进行处理，以下图

  

这种输入模型在android的系统中不少地方采用，先从最底层提及：

 为了因为触屏事件频率很高，android设计者讲一个循环线程，拆分为两级循环，并作了个队列来进行缓冲。

InputDispatcherThread和InputReaderThread

         InputDispatcherThread在本身的循环中对InputReaderThread请求同步，InputReaderThread收到同步信号后，把事件放入InputDispatcher的队列中。

具体代码以下：

InputReader.cpp中有不少InputMapper,有SwitchInputMapper，KeyBoardInputMapper，TrackballInputMapper，SingleTouchInputMapper，

MultiTouchInputMapper。当线程从EventHub读取到Event后，调用这些InputMapper的pocess方法：

 

文件InputReader.cpp中： bool InputReaderThread::threadLoop() { mReader->loopOnce(); return true; } void InputReader::loopOnce() { RawEvent rawEvent; mEventHub->getEvent(& rawEvent); #if DEBUG_RAW_EVENTS LOGD("Input event: device=0x%x type=0x%x scancode=%d keycode=%d value=%d", rawEvent.deviceId, rawEvent.type, rawEvent.scanCode, rawEvent.keyCode, rawEvent.value); #endif process(& rawEvent); }

 process以下

void InputReader::process(const RawEvent* rawEvent) { switch (rawEvent->type) { consumeEvent(rawEvent); break; } }

 

 

consumeEvent(rawEvent);

consumeEvent(rawEvent);

方法是关键，下面继续跟进；

 

Java代码  

void InputReader::consumeEvent(const RawEvent* rawEvent) { int32_t deviceId = rawEvent->deviceId; { device->process(rawEvent); } // release device registry reader lock }

   device->process(rawEvent)行， 跟进去：

Java代码  

void InputDevice::process(const RawEvent* rawEvent) { size_t numMappers = mMappers.size(); for (size_t i = 0; i < numMappers; i++) { InputMapper* mapper = mMappers[i]; mapper->process(rawEvent); } }

 下面进入了IputMapper，InputMapper是个纯虚类，process是个纯虚方法，随便找个例子跟进去：

void SingleTouchInputMapper::process(const RawEvent* rawEvent) { switch (rawEvent->type) { case EV_KEY: switch (rawEvent->scanCode) { case BTN_TOUCH: mAccumulator.fields |= Accumulator::FIELD_BTN_TOUCH; mAccumulator.btnTouch = rawEvent->value != 0; // Don't sync immediately. Wait until the next SYN_REPORT since we might // not have received valid position information yet. This logic assumes that // BTN_TOUCH is always followed by SYN_REPORT as part of a complete packet. break; } break; case EV_SYN: switch (rawEvent->scanCode) { case SYN_REPORT: sync(rawEvent->when); break; } break; } }

 最关键的是

sync(rawEvent->when);

sync(rawEvent->when);

  展开以下：

 

Cpp代码  

void SingleTouchInputMapper::sync(nsecs_t when) { syncTouch(when, true); }

 

Java代码  

void TouchInputMapper::syncTouch(nsecs_t when, bool havePointerIds) { if (touchResult == DISPATCH_TOUCH) { detectGestures(when); dispatchTouches(when, policyFlags); } }

 

 这两行，一个是虚拟键盘，一个是触摸屏。

      TouchResult touchResult = consumeOffScreenTouches(when, policyFlags);

dispatchTouches
 
    void TouchInputMapper::dispatchTouches(nsecs_t when, uint32_t policyFlags) {
        // Dispatch pointer down events using the new pointer locations.
        while (!downIdBits.isEmpty()) {
            dispatchTouch(when, policyFlags, &mCurrentTouch,
                    activeIdBits, downId, pointerCount, motionEventAction);
        }
    }
} void TouchInputMapper::dispatchTouches(nsecs_t when, uint32_t policyFlags) { // Dispatch pointer down events using the new pointer locations. while (!downIdBits.isEmpty()) { dispatchTouch(when, policyFlags, &mCurrentTouch, activeIdBits, downId, pointerCount, motionEventAction); } } }   
    dispatchTouch(when, policyFlags, &mCurrentTouch,
                    activeIdBits, downId, pointerCount, motionEventAction); dispatchTouch(when, policyFlags, &mCurrentTouch, activeIdBits, downId, pointerCount, motionEventAction);这个方法展开以下：   
    void TouchInputMapper::dispatchTouch(nsecs_t when, uint32_t policyFlags,
        TouchData* touch, BitSet32 idBits, uint32_t changedId, uint32_t pointerCount,
        int32_t motionEventAction) {
    int32_t pointerIds[MAX_POINTERS];
    PointerCoords pointerCoords[MAX_POINTERS];
    int32_t motionEventEdgeFlags = 0;
    float xPrecision, yPrecision;

    {
    getDispatcher()->notifyMotion(when, getDeviceId(), getSources(), policyFlags,
            motionEventAction, 0, getContext()->getGlobalMetaState(), motionEventEdgeFlags,
            pointerCount, pointerIds, pointerCoords,
            xPrecision, yPrecision, mDownTime);
} void TouchInputMapper::dispatchTouch(nsecs_t when, uint32_t policyFlags, TouchData* touch, BitSet32 idBits, uint32_t changedId, uint32_t pointerCount, int32_t motionEventAction) { int32_t pointerIds[MAX_POINTERS]; PointerCoords pointerCoords[MAX_POINTERS]; int32_t motionEventEdgeFlags = 0; float xPrecision, yPrecision; { getDispatcher()->notifyMotion(when, getDeviceId(), getSources(), policyFlags, motionEventAction, 0, getContext()->getGlobalMetaState(), motionEventEdgeFlags, pointerCount, pointerIds, pointerCoords, xPrecision, yPrecision, mDownTime); }     这样就到了InputDiaptcher的notifyMotion方法，这个方法很长，都再处理MOVE事件，将无用的删除后，留下以下关键代码：   
     void InputDispatcher::notifyMotion(nsecs_t eventTime, int32_t deviceId, int32_t source,
        uint32_t policyFlags, int32_t action, int32_t flags, int32_t metaState, int32_t edgeFlags,
        uint32_t pointerCount, const int32_t* pointerIds, const PointerCoords* pointerCoords,
        float xPrecision, float yPrecision, nsecs_t downTime) {

 // Just enqueue a new motion event.
        MotionEntry* newEntry = mAllocator.obtainMotionEntry(eventTime,
                deviceId, source, policyFlags, action, flags, metaState, edgeFlags,
                xPrecision, yPrecision, downTime,
                pointerCount, pointerIds, pointerCoords);

        needWake = enqueueInboundEventLocked(newEntry);
} void InputDispatcher::notifyMotion(nsecs_t eventTime, int32_t deviceId, int32_t source, uint32_t policyFlags, int32_t action, int32_t flags, int32_t metaState, int32_t edgeFlags, uint32_t pointerCount, const int32_t* pointerIds, const PointerCoords* pointerCoords, float xPrecision, float yPrecision, nsecs_t downTime) { // Just enqueue a new motion event. MotionEntry* newEntry = mAllocator.obtainMotionEntry(eventTime, deviceId, source, policyFlags, action, flags, metaState, edgeFlags, xPrecision, yPrecision, downTime, pointerCount, pointerIds, pointerCoords); needWake = enqueueInboundEventLocked(newEntry); } 最后一句： 
    needWake = enqueueInboundEventLocked(newEntry); needWake = enqueueInboundEventLocked(newEntry);  
    bool InputDispatcher::enqueueInboundEventLocked(EventEntry* entry) {
    bool needWake = mInboundQueue.isEmpty();
    mInboundQueue.enqueueAtTail(entry);

    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;
            } else if (keyEntry->action == AKEY_EVENT_ACTION_UP) {
                if (mAppSwitchSawKeyDown) {
#if DEBUG_APP_SWITCH
                    LOGD("App switch is pending!");
#endif
                    mAppSwitchDueTime = keyEntry->eventTime + APP_SWITCH_TIMEOUT;
                    mAppSwitchSawKeyDown = false;
                    needWake = true;
                }
            }
        }
        break;
    }
    }

    return needWake;
} bool InputDispatcher::enqueueInboundEventLocked(EventEntry* entry) { bool needWake = mInboundQueue.isEmpty(); mInboundQueue.enqueueAtTail(entry); 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; } else if (keyEntry->action == AKEY_EVENT_ACTION_UP) { if (mAppSwitchSawKeyDown) { #if DEBUG_APP_SWITCH LOGD("App switch is pending!"); #endif mAppSwitchDueTime = keyEntry->eventTime + APP_SWITCH_TIMEOUT; mAppSwitchSawKeyDown = false; needWake = true; } } } break; } } return needWake; }   
    mInboundQueue正是上面所说的队列。到此为止，从InputReader插入到队列就完成了。 mInboundQueue正是上面所说的队列。到此为止，从InputReader插入到队列就完成了。 那么InputDispatcher又是如何从队列中取出来的呢？累了。   InputDiapather的 
    dispatchOnce dispatchOnce方法以下： 
    void InputDispatcher::dispatchOnce() {
    nsecs_t keyRepeatTimeout = mPolicy->getKeyRepeatTimeout();
    nsecs_t keyRepeatDelay = mPolicy->getKeyRepeatDelay();

    nsecs_t nextWakeupTime = LONG_LONG_MAX;
    { // acquire lock
        AutoMutex _l(mLock);
        dispatchOnceInnerLocked(keyRepeatTimeout, keyRepeatDelay, & nextWakeupTime);

        if (runCommandsLockedInterruptible()) {
            nextWakeupTime = LONG_LONG_MIN;  // force next poll to wake up immediately
        }
    } // release lock

    // Wait for callback or timeout or wake.  (make sure we round up, not down)
    nsecs_t currentTime = now();
    int32_t timeoutMillis;
    if (nextWakeupTime > currentTime) {
        uint64_t timeout = uint64_t(nextWakeupTime - currentTime);
        timeout = (timeout + 999999LL) / 1000000LL;
        timeoutMillis = timeout > INT_MAX ? -1 : int32_t(timeout);
    } else {
        timeoutMillis = 0;
    }

    mLooper->pollOnce(timeoutMillis);
} void InputDispatcher::dispatchOnce() { nsecs_t keyRepeatTimeout = mPolicy->getKeyRepeatTimeout(); nsecs_t keyRepeatDelay = mPolicy->getKeyRepeatDelay(); nsecs_t nextWakeupTime = LONG_LONG_MAX; { // acquire lock AutoMutex _l(mLock); dispatchOnceInnerLocked(keyRepeatTimeout, keyRepeatDelay, & nextWakeupTime); if (runCommandsLockedInterruptible()) { nextWakeupTime = LONG_LONG_MIN; // force next poll to wake up immediately } } // release lock // Wait for callback or timeout or wake. (make sure we round up, not down) nsecs_t currentTime = now(); int32_t timeoutMillis; if (nextWakeupTime > currentTime) { uint64_t timeout = uint64_t(nextWakeupTime - currentTime); timeout = (timeout + 999999LL) / 1000000LL; timeoutMillis = timeout > INT_MAX ? -1 : int32_t(timeout); } else { timeoutMillis = 0; } mLooper->pollOnce(timeoutMillis); } 最关键的是 
    dispatchOnceInnerLocked(keyRepeatTimeout, keyRepeatDelay, & nextWakeupTime); dispatchOnceInnerLocked(keyRepeatTimeout, keyRepeatDelay, & nextWakeupTime); 和 
        mLooper->pollOnce(timeoutMillis);（这个方法在有个回调，与事件有关的是【管道设备的文件描述符】。
  具体机制在后面讲。这个东西其实是个跨进程的信号。发送给了Android的用户进程的JNI，又经过JNI调用InputQueue的的
静态方法如：dispatchMotionEvent。后面回提到dispatchMotionEvent才是Android用户进程的事件入口函数。）
） mLooper->pollOnce(timeoutMillis);（这个方法在有个回调，与事件有关的是【管道设备的文件描述符】。 具体机制在后面讲。这个东西其实是个跨进程的信号。发送给了Android的用户进程的JNI，又经过JNI调用InputQueue的的 静态方法如：dispatchMotionEvent。后面回提到dispatchMotionEvent才是Android用户进程的事件入口函数。） ）代码又长又臭     
    void InputDispatcher::dispatchOnceInnerLocked(nsecs_t keyRepeatTimeout,
        nsecs_t keyRepeatDelay, nsecs_t* nextWakeupTime) {
    case EventEntry::TYPE_MOTION: {
        MotionEntry* typedEntry = static_cast<MotionEntry*>(mPendingEvent);
        if (dropReason == DROP_REASON_NOT_DROPPED && isAppSwitchDue) {
            dropReason = DROP_REASON_APP_SWITCH;
        }
        done = dispatchMotionLocked(currentTime, typedEntry,
                &dropReason, nextWakeupTime);
        break;
    }

} void InputDispatcher::dispatchOnceInnerLocked(nsecs_t keyRepeatTimeout, nsecs_t keyRepeatDelay, nsecs_t* nextWakeupTime) { case EventEntry::TYPE_MOTION: { MotionEntry* typedEntry = static_cast<MotionEntry*>(mPendingEvent); if (dropReason == DROP_REASON_NOT_DROPPED && isAppSwitchDue) { dropReason = DROP_REASON_APP_SWITCH; } done = dispatchMotionLocked(currentTime, typedEntry, &dropReason, nextWakeupTime); break; } }   
    dispatchMotionLocked dispatchMotionLocked方法调用prepareDispatchCycleLocked，调用startDispatchCycleLocked，最终调用        // Publish the key event.         status = connection->inputPublisher.publishKeyEvent(keyEntry->deviceId, keyEntry->source,                 action, flags, keyEntry->keyCode, keyEntry->scanCode,                 keyEntry->metaState, keyEntry->repeatCount, keyEntry->downTime,                 keyEntry->eventTime); 或者 // Publish the motion event and the first motion sample.         status = connection->inputPublisher.publishMotionEvent(motionEntry->deviceId,                 motionEntry->source, action, flags, motionEntry->edgeFlags, motionEntry->metaState,                 xOffset, yOffset,                 motionEntry->xPrecision, motionEntry->yPrecision,                 motionEntry->downTime, firstMotionSample->eventTime,                 motionEntry->pointerCount, motionEntry->pointerIds,                 firstMotionSample->pointerCoords);   至此，InputDisapatcher也结束了。 既然发布出去，必然有订阅者：在InputTransport.cpp中 
    status_t InputConsumer::consume(InputEventFactoryInterface* factory, InputEvent** outEvent) {
#if DEBUG_TRANSPORT_ACTIONS
    LOGD("channel '%s' consumer ~ consume",
            mChannel->getName().string());
#endif

    *outEvent = NULL;

    int ashmemFd = mChannel->getAshmemFd();
    int result = ashmem_pin_region(ashmemFd, 0, 0);
    if (result != ASHMEM_NOT_PURGED) {
        if (result == ASHMEM_WAS_PURGED) {
            LOGE("channel '%s' consumer ~ Error %d pinning ashmem fd %d because it was purged "
                    "which probably indicates that the publisher and consumer are out of sync.",
                    mChannel->getName().string(), result, ashmemFd);
            return INVALID_OPERATION;
        }

        LOGE("channel '%s' consumer ~ Error %d pinning ashmem fd %d.",
                mChannel->getName().string(), result, ashmemFd);
        return UNKNOWN_ERROR;
    }

    if (mSharedMessage->consumed) {
        LOGE("channel '%s' consumer ~ The current message has already been consumed.",
                mChannel->getName().string());
        return INVALID_OPERATION;
    }

    // Acquire but *never release* the semaphore.  Contention on the semaphore is used to signal
    // to the publisher that the message has been consumed (or is in the process of being
    // consumed).  Eventually the publisher will reinitialize the semaphore for the next message.
    result = sem_wait(& mSharedMessage->semaphore);
    if (result < 0) {
        LOGE("channel '%s' consumer ~ Error %d in sem_wait.",
                mChannel->getName().string(), errno);
        return UNKNOWN_ERROR;
    }

    mSharedMessage->consumed = true;

    switch (mSharedMessage->type) {
    case AINPUT_EVENT_TYPE_KEY: {
        KeyEvent* keyEvent = factory->createKeyEvent();
        if (! keyEvent) return NO_MEMORY;

        populateKeyEvent(keyEvent);

        *outEvent = keyEvent;
        break;
    }

    case AINPUT_EVENT_TYPE_MOTION: {
        MotionEvent* motionEvent = factory->createMotionEvent();
        if (! motionEvent) return NO_MEMORY;

        populateMotionEvent(motionEvent);

        *outEvent = motionEvent;
        break;
    }

    default:
        LOGE("channel '%s' consumer ~ Received message of unknown type %d",
                mChannel->getName().string(), mSharedMessage->type);
        return UNKNOWN_ERROR;
    }

    return OK;
} status_t InputConsumer::consume(InputEventFactoryInterface* factory, InputEvent** outEvent) { #if DEBUG_TRANSPORT_ACTIONS LOGD("channel '%s' consumer ~ consume", mChannel->getName().string()); #endif *outEvent = NULL; int ashmemFd = mChannel->getAshmemFd(); int result = ashmem_pin_region(ashmemFd, 0, 0); if (result != ASHMEM_NOT_PURGED) { if (result == ASHMEM_WAS_PURGED) { LOGE("channel '%s' consumer ~ Error %d pinning ashmem fd %d because it was purged " "which probably indicates that the publisher and consumer are out of sync.", mChannel->getName().string(), result, ashmemFd); return INVALID_OPERATION; } LOGE("channel '%s' consumer ~ Error %d pinning ashmem fd %d.", mChannel->getName().string(), result, ashmemFd); return UNKNOWN_ERROR; } if (mSharedMessage->consumed) { LOGE("channel '%s' consumer ~ The current message has already been consumed.", mChannel->getName().string()); return INVALID_OPERATION; } // Acquire but *never release* the semaphore. Contention on the semaphore is used to signal // to the publisher that the message has been consumed (or is in the process of being // consumed). Eventually the publisher will reinitialize the semaphore for the next message. result = sem_wait(& mSharedMessage->semaphore); if (result < 0) { LOGE("channel '%s' consumer ~ Error %d in sem_wait.", mChannel->getName().string(), errno); return UNKNOWN_ERROR; } mSharedMessage->consumed = true; switch (mSharedMessage->type) { case AINPUT_EVENT_TYPE_KEY: { KeyEvent* keyEvent = factory->createKeyEvent(); if (! keyEvent) return NO_MEMORY; populateKeyEvent(keyEvent); *outEvent = keyEvent; break; } case AINPUT_EVENT_TYPE_MOTION: { MotionEvent* motionEvent = factory->createMotionEvent(); if (! motionEvent) return NO_MEMORY; populateMotionEvent(motionEvent); *outEvent = motionEvent; break; } default: LOGE("channel '%s' consumer ~ Received message of unknown type %d", mChannel->getName().string(), mSharedMessage->type); return UNKNOWN_ERROR; } return OK; }  也许咱们最关心的是如何订阅的，不得不取看一下JNI的代码，文件android_view_InputQueue.cpp   聚焦到这里   
    status_t NativeInputQueue::registerInputChannel(JNIEnv* env, jobject inputChannelObj,
        jobject inputHandlerObj, jobject messageQueueObj) {
    sp<InputChannel> inputChannel = android_view_InputChannel_getInputChannel(env,
            inputChannelObj);
    if (inputChannel == NULL) {
        LOGW("Input channel is not initialized.");
        return BAD_VALUE;
    }

#if DEBUG_REGISTRATION
    LOGD("channel '%s' - Registered", inputChannel->getName().string());
#endif

    sp<Looper> looper = android_os_MessageQueue_getLooper(env, messageQueueObj);

    { // acquire lock
        AutoMutex _l(mLock);

        if (getConnectionIndex(inputChannel) >= 0) {
            LOGW("Attempted to register already registered input channel '%s'",
                    inputChannel->getName().string());
            return BAD_VALUE;
        }

        uint16_t connectionId = mNextConnectionId++;
        sp<Connection> connection = new Connection(connectionId, inputChannel, looper);
        status_t result = connection->inputConsumer.initialize();
        if (result) {
            LOGW("Failed to initialize input consumer for input channel '%s', status=%d",
                    inputChannel->getName().string(), result);
            return result;
        }

        connection->inputHandlerObjGlobal = env->NewGlobalRef(inputHandlerObj);

        int32_t receiveFd = inputChannel->getReceivePipeFd();
        mConnectionsByReceiveFd.add(receiveFd, connection);

        looper->addFd(receiveFd, 0, ALOOPER_EVENT_INPUT, handleReceiveCallback, this);
    } // release lock

    android_view_InputChannel_setDisposeCallback(env, inputChannelObj,
            handleInputChannelDisposed, this);
    return OK;
} status_t NativeInputQueue::registerInputChannel(JNIEnv* env, jobject inputChannelObj, jobject inputHandlerObj, jobject messageQueueObj) { sp<InputChannel> inputChannel = android_view_InputChannel_getInputChannel(env, inputChannelObj); if (inputChannel == NULL) { LOGW("Input channel is not initialized."); return BAD_VALUE; } #if DEBUG_REGISTRATION LOGD("channel '%s' - Registered", inputChannel->getName().string()); #endif sp<Looper> looper = android_os_MessageQueue_getLooper(env, messageQueueObj); { // acquire lock AutoMutex _l(mLock); if (getConnectionIndex(inputChannel) >= 0) { LOGW("Attempted to register already registered input channel '%s'", inputChannel->getName().string()); return BAD_VALUE; } uint16_t connectionId = mNextConnectionId++; sp<Connection> connection = new Connection(connectionId, inputChannel, looper); status_t result = connection->inputConsumer.initialize(); if (result) { LOGW("Failed to initialize input consumer for input channel '%s', status=%d", inputChannel->getName().string(), result); return result; } connection->inputHandlerObjGlobal = env->NewGlobalRef(inputHandlerObj); int32_t receiveFd = inputChannel->getReceivePipeFd(); mConnectionsByReceiveFd.add(receiveFd, connection); looper->addFd(receiveFd, 0, ALOOPER_EVENT_INPUT, handleReceiveCallback, this); } // release lock android_view_InputChannel_setDisposeCallback(env, inputChannelObj, handleInputChannelDisposed, this); return OK; }      也许更想知道的是消息队列在什么地方，进入InputQueue.java来看   
    public static void registerInputChannel(InputChannel inputChannel, InputHandler inputHandler,
        MessageQueue messageQueue) {
    if (inputChannel == null) {
        throw new IllegalArgumentException("inputChannel must not be null");
    }
    if (inputHandler == null) {
        throw new IllegalArgumentException("inputHandler must not be null");
    }
    if (messageQueue == null) {
        throw new IllegalArgumentException("messageQueue must not be null");
    }

    synchronized (sLock) {
        if (DEBUG) {
            Slog.d(TAG, "Registering input channel '" + inputChannel + "'");
        }

        nativeRegisterInputChannel(inputChannel, inputHandler, messageQueue);
    }
} public static void registerInputChannel(InputChannel inputChannel, InputHandler inputHandler, MessageQueue messageQueue) { if (inputChannel == null) { throw new IllegalArgumentException("inputChannel must not be null"); } if (inputHandler == null) { throw new IllegalArgumentException("inputHandler must not be null"); } if (messageQueue == null) { throw new IllegalArgumentException("messageQueue must not be null"); } synchronized (sLock) { if (DEBUG) { Slog.d(TAG, "Registering input channel '" + inputChannel + "'"); } nativeRegisterInputChannel(inputChannel, inputHandler, messageQueue); } }   在ViewRoot.java中有这么几行   
    InputQueue.registerInputChannel(mInputChannel, mInputHandler,
        Looper.myQueue()); InputQueue.registerInputChannel(mInputChannel, mInputHandler, Looper.myQueue()); 完毕。 这才牵涉到管道的问题，哪一个Java中的Channel对应的正是linux系统的管道。有了管道，才能经过 跨进程方式回调回来，为何是这个入口，上面进行了解释。具体参照INputQUEUE这个java类的JNI方法 int NativeInputQueue::handleReceiveCallback(int receiveFd, int events, void* data) 这个方法被InputQueue的RegisterInputChannel注册给了系统.系统经过回调，回调的是这个ALOOPER_EVENT_INPUT事件。     looper就是android中的【用户进程的循环】 注册的代码为 ：   looper->addFd(receiveFd, 0, ALOOPER_EVENT_INPUT, handleReceiveCallback, this); 回调的java函数为 
    
回调的java代码的方法入口为：InputQueue.java中的。

@SuppressWarnings("unused")
    private static void dispatchMotionEvent(InputHandler inputHandler,
            MotionEvent event, long finishedToken) {
        Runnable finishedCallback = FinishedCallback.obtain(finishedToken);
        inputHandler.handleMotion(event, finishedCallback);
    } 回调的java代码的方法入口为：InputQueue.java中的。 @SuppressWarnings("unused") private static void dispatchMotionEvent(InputHandler inputHandler, MotionEvent event, long finishedToken) { Runnable finishedCallback = FinishedCallback.obtain(finishedToken); inputHandler.handleMotion(event, finishedCallback); } 这样就回调到了ViewRoot中

dispatchTouches

    只说触摸屏，虚拟键相似，触摸屏调用的是