资源网站：
http://evgeny-goldin.com/blog/3-ways-install-git-linux-ubuntu/
欢迎光临 www.51droidgame.com 网站进行讨论。上一篇介绍把top level的View的InputChannel其挂入到android系统中的机制给讲了，但是并没有解释如何驱动的，本篇就如何驱动来进行讲述。
先讲一下基本一般的输入处理方式的知识。一般的输入输出采用生产者，消费者模式，并构造队列进行处理，如下图
?? 
这种输入模型在android的系统中很多地方采用，先从最底层说起：
?为了由于触屏事件频率很高，android设计者讲一个循环线程，拆分为两级循环，并做了个队列来进行缓冲。
InputDispatcherThread和InputReaderThread。InputDispatcherThread在自己的循环中对InputReaderThread请求同步，InputReaderThread收到同步信号后，把事件放入InputDispatcher的队列中。
具体代码如下：
InputReader.cpp中有很多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如下
? void InputReader::process(const RawEvent* rawEvent) {
??? switch (rawEvent->type) {
??? default:
??????? consumeEvent(rawEvent);
??????? break;
??? }
}
void InputReader::process(const RawEvent* rawEvent) { switch (rawEvent->type) { consumeEvent(rawEvent); break; }}?
?
consumeEvent(rawEvent);
方法是关键，下面继续跟进；
?
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：
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);
? 展开如下：
?
void SingleTouchInputMapper::sync(nsecs_t when) { syncTouch(when, true); }?
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
? ? 只说触摸屏，虚拟键类似，触摸屏调用的是 ?
?
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);
这个方法展开如下：
?
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);}?
? 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，留下如下关键代码：
?
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);}?最后一句：
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;}?
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
方法如下：
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);}?最关键的是
dispatchOnceInnerLocked(keyRepeatTimeout, keyRepeatDelay, & nextWakeupTime);
和
mLooper->pollOnce(timeoutMillis);//这个是个回调。
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; }}?
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);
?
??? 然后// Send the dispatch signal.
??? status = connection->inputPublisher.sendDispatchSignal();
??? if (status) {
??????? LOGE("channel '%s' ~ Could not send dispatch signal, status=%d",
??????????????? connection->getInputChannelName(), status);
??????? abortBrokenDispatchCycleLocked(currentTime, connection);
??????? return;
??? }
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;}?也许我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;}?
?
? 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); } } ?
在ViewRoot.java中有这么几行
?
InputQueue.registerInputChannel(mInputChannel, mInputHandler, Looper.myQueue());
?完毕。
这才牵涉到管道的问题，哪个Java中的Channel对应的正是linux系统的管道。有了管道，才能通过 跨进程方式回调回来，为什么是这个入口，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.系统通过回调，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); }?这样就回调到了ViewRoot中
?
?
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