前言
上一篇文章中，对于事件的监控和获取做了分析，在拿到事件之后，后续是如何处理分发的呢？本篇文章主要针对在通过getEvent获取到事件之后，后续的相关分发处理流程。
InputReaderThread函数不断地调用looperOnce函数，不断的从中读取事件，那么下一个问题来了，读取到事件要放置到哪里，又在哪里被消耗掉了呢？也就是事件接下来的流向问题。让我们回到looperOnce之前。
事件分发
processEventsLocked
在调用了getEvent之后，获得了事件之后，接着调用了相应的处理函数processEventsLocked
void InputReader::processEventsLocked(const RawEvent* rawEvents, size_t count) {
for (const RawEvent* rawEvent = rawEvents; count;) {
int32_t type = rawEvent->type;
size_t batchSize = 1;
if (type < EventHubInterface::FIRST_SYNTHETIC_EVENT) {
int32_t deviceId = rawEvent->deviceId;
while (batchSize < count) {
if (rawEvent[batchSize].type >= EventHubInterface::FIRST_SYNTHETIC_EVENT
|| rawEvent[batchSize].deviceId != deviceId) {
break;
}
batchSize += 1;
}
processEventsForDeviceLocked(deviceId, rawEvent, batchSize);
} else {
switch (rawEvent->type) {
case EventHubInterface::DEVICE_ADDED:
addDeviceLocked(rawEvent->when, rawEvent->deviceId);
break;
case EventHubInterface::DEVICE_REMOVED:
removeDeviceLocked(rawEvent->when, rawEvent->deviceId);
break;
case EventHubInterface::FINISHED_DEVICE_SCAN:
handleConfigurationChangedLocked(rawEvent->when);
break;
default:
ALOG_ASSERT(false); // can't happen
break;
}
}
count -= batchSize;
rawEvent += batchSize;
}
}
首先对于事件类型进行了判断，如果事件不是合成事件，则会对其DeviceID进行判断，通过对其判断来确定batchSize等，如果是合成事件，则会具体判断，判断是设备的添加，设备的移除，完成设备扫描等等，然后对事件分别进行处理，这里我们只关心对于设备自身产生的事件。也就是触摸屏相关的事件。也就是processEventsForDeviceLocked函数中所进行的操作。
事件派发到InputDevice
void InputReader::processEventsForDeviceLocked(int32_t deviceId,
const RawEvent* rawEvents, size_t count) {
ssize_t deviceIndex = mDevices.indexOfKey(deviceId);
if (deviceIndex < 0) {
return;
}
InputDevice* device = mDevices.valueAt(deviceIndex);
if (device->isIgnored()) {
return;
}
device->process(rawEvents, count);
}
根据事件获得相应的设备类型，然后将事件交给相应的设备处理。判断是否忽略该事件，如果不是忽略该事件，则会调用相应设备的process方法进行处理。
事件派发到InputMapper
InputDevice的process方法
void InputDevice::process(const RawEvent* rawEvents, size_t count) {
....
for (size_t i = 0; i < numMappers; i++) {
InputMapper* mapper = mMappers[i];
mapper->process(rawEvent);
}
....
}
这里的事件又交给了InputMapper来处理
InputMapper对应了很多的子类，这里根据事件的类型进行相应的派发，处理。事件到了这里之后，这里来看一下对于触摸屏事件的处理的相关类和处理函数。
void TouchInputMapper::process(const RawEvent* rawEvent) {
mCursorButtonAccumulator.process(rawEvent);
mCursorScrollAccumulator.process(rawEvent);
mTouchButtonAccumulator.process(rawEvent);
if (rawEvent->type == EV_SYN && rawEvent->code == SYN_REPORT) {
sync(rawEvent->when);
}
}
通过这里的函数处理，我们继续追踪函数的数据流向。对于相关事件会调用TouchInputMapper的sync方法来进行处理。
void TouchInputMapper::sync(nsecs_t when) {
.....
processRawTouches(false /*timeout*/);
}
void TouchInputMapper::processRawTouches(bool timeout) {
....
cookAndDispatch(mCurrentRawState.when);
....
}
在相关的函数调用之后，最终调用了dispatchTouches
void TouchInputMapper::dispatchTouches(nsecs_t when, uint32_t policyFlags) {
....
dispatchMotion();
....
}
对于dispatchTouches中，会根据记录的上一次的触摸位置，对事件的类型进行判断，然后做相应的分发，事件类型有抬起，下落，移动等，然后对相应的事件进行分发。无论是对于何种类型的事件派发，最终被调用到的都是dispatchMotion()方法。
对于相关事件的分发最终调用到了dispatchMotion()，对事件数据进行组装之后，调用了
void TouchInputMapper::dispatchMotion() {
....
NotifyMotionArgs args(when, getDeviceId(), source, policyFlags,
action, actionButton, flags, metaState, buttonState, edgeFlags,
mViewport.displayId, pointerCount, pointerProperties, pointerCoords,
xPrecision, yPrecision, downTime);
getListener()->notifyMotion(&args);
}
这里对于事件进行了封装，构造出一个NotifyMotionArgs，在整个传递流程做的比较多的就是通过对于事件进行一系列的判断，然后进行一系列的封装。接下来的执行是调用QueuedInputListener的notifyMotion，将构造的事件添加到其中的一个Args队列之中。
InputListenerInterface* InputReader::ContextImpl::getListener() {
return mReader->mQueuedListener.get();
}
notifyMotion函数实现
void QueuedInputListener::notifyMotion(const NotifyMotionArgs* args) {
mArgsQueue.push(new NotifyMotionArgs(*args));
}
之后又调用了QueuedInputListener的flush方法。遍历事件的队列，然后对其逐一调用notify函数。
void QueuedInputListener::flush() {
size_t count = mArgsQueue.size();
for (size_t i = 0; i < count; i++) {
NotifyArgs* args = mArgsQueue[i];
args->notify(mInnerListener);
delete args;
}
mArgsQueue.clear();
}
NotifyArgs的notify函数实现
void NotifyMotionArgs::notify(const sp<InputListenerInterface>& listener) const {
listener->notifyMotion(this);
}
对于这个listener的创建来自于InputReader构建的时候。
mQueuedListener = new QueuedInputListener(listener);
mReader = new InputReader(eventHub, readerPolicy, mDispatcher);
而这里的Listener则是InputDispatcher，InputDispatcher 的notifyMotion实现源码。
void InputDispatcher::notifyMotion(const NotifyMotionArgs* args) {
.....
MotionEvent event;
event.initialize(args->deviceId, args->source, args->action, args->actionButton,
args->flags, args->edgeFlags, args->metaState, args->buttonState,
0, 0, args->xPrecision, args->yPrecision,
args->downTime, args->eventTime,
args->pointerCount, args->pointerProperties, args->pointerCoords);
....
MotionEntry* newEntry = new MotionEntry(args->eventTime,
args->deviceId, args->source, policyFlags,
args->action, args->actionButton, args->flags,
args->metaState, args->buttonState,
args->edgeFlags, args->xPrecision, args->yPrecision, args->downTime,
args->displayId,
args->pointerCount, args->pointerProperties, args->pointerCoords, 0, 0);
needWake = enqueueInboundEventLocked(newEntry);
....
if (needWake) {
mLooper->wake();
}
}
在该函数中，所做的事情是对于所传递的参数，构造MotionEntry，然后将其加入到enqueueInboundEventLocked之中。然后唤醒其中的looper。
bool InputDispatcher::enqueueInboundEventLocked(EventEntry* entry) {
bool needWake = mInboundQueue.isEmpty();
mInboundQueue.enqueueAtTail(entry);
...
//进行一些事件和窗口相关的判断处理
}
Dispatcher开启的线程中，每次循环的操作如何？
bool InputDispatcherThread::threadLoop() {
mDispatcher->dispatchOnce();
return true;
}
Dispatcher下dispatchOnce的实现
void InputDispatcher::dispatchOnce() {
...
dispatchOnceInnerLocked(&nextWakeupTime);
...
}
void InputDispatcher::dispatchOnceInnerLocked(nsecs_t* nextWakeupTime) {
....
mPendingEvent = mInboundQueue.dequeueAtHead();
....
switch (mPendingEvent->type) {
case EventEntry::TYPE_MOTION: {
MotionEntry* typedEntry = static_cast<MotionEntry*>(mPendingEvent);
if (dropReason == DROP_REASON_NOT_DROPPED && isAppSwitchDue) {
dropReason = DROP_REASON_APP_SWITCH;
}
if (dropReason == DROP_REASON_NOT_DROPPED
&& isStaleEventLocked(currentTime, typedEntry)) {
dropReason = DROP_REASON_STALE;
}
if (dropReason == DROP_REASON_NOT_DROPPED && mNextUnblockedEvent) {
dropReason = DROP_REASON_BLOCKED;
}
done = dispatchMotionLocked(currentTime, typedEntry,
&dropReason, nextWakeupTime);
break;
}
....
}
}
从mInboudQueue中，获取到事件，然后对事件类型进行判断，判断之后调用了dispatchMotionLocked函数，来继续进行事件的传递。
bool InputDispatcher::dispatchMotionLocked(
nsecs_t currentTime, MotionEntry* entry, DropReason* dropReason, nsecs_t* nextWakeupTime) {
....
Vector<InputTarget> inputTargets;
if (isPointerEvent) {
// Pointer event. (eg. touchscreen)
//寻找目标窗口
injectionResult = findTouchedWindowTargetsLocked(currentTime,
entry, inputTargets, nextWakeupTime, &conflictingPointerActions);
} else {
// Non touch event. (eg. trackball）
injectionResult = findFocusedWindowTargetsLocked(currentTime,
entry, inputTargets, nextWakeupTime);
}
....
dispatchEventLocked(currentTime, entry, inputTargets);
return true;
}
- dispatchEventLocked
void InputDispatcher::dispatchEventLocked(nsecs_t currentTime,
EventEntry* eventEntry, const Vector<InputTarget>& inputTargets) {
....
pokeUserActivityLocked(eventEntry);
.....
for (size_t i = 0; i < inputTargets.size(); i++) {
const InputTarget& inputTarget = inputTargets.itemAt(i);
ssize_t connectionIndex = getConnectionIndexLocked(inputTarget.inputChannel);
if (connectionIndex >= 0) {
sp<Connection> connection = mConnectionsByFd.valueAt(connectionIndex);
prepareDispatchCycleLocked(currentTime, connection, eventEntry, &inputTarget);
}
}
}
获得目标输入，根据InputChannel获取相应的连接，然后调用prepareDispatchCycleLocked()，进行事件的派发。
enqueueDispatchEntriesLocked，在该方法中又调用了startDispatchCycleLocked方法。其实现为
void InputDispatcher::startDispatchCycleLocked(nsecs_t currentTime,
const sp<Connection>& connection) {
EventEntry* eventEntry = dispatchEntry->eventEntry;
....
switch (eventEntry->type) {
....
case EventEntry::TYPE_MOTION: {
status = connection->inputPublisher.publishMotionEvent( ....);
break;
}
....
}
...
}
至此调用了connection 的inputPublisher的publishMotionEvent方法将事件分发消耗。
InputPublisher定义在InputTransport.cpp中
status_t InputPublisher::publishMotionEvent(...) {
....
InputMessage msg;
msg.header.type = InputMessage::TYPE_MOTION;
msg.body.motion.seq = seq;
msg.body.motion.deviceId = deviceId;
msg.body.motion.source = source;
msg.body.motion.action = action;
msg.body.motion.actionButton = actionButton;
msg.body.motion.flags = flags;
msg.body.motion.edgeFlags = edgeFlags;
msg.body.motion.metaState = metaState;
msg.body.motion.buttonState = buttonState;
msg.body.motion.xOffset = xOffset;
msg.body.motion.yOffset = yOffset;
msg.body.motion.xPrecision = xPrecision;
msg.body.motion.yPrecision = yPrecision;
msg.body.motion.downTime = downTime;
msg.body.motion.eventTime = eventTime;
msg.body.motion.pointerCount = pointerCount;
for (uint32_t i = 0; i < pointerCount; i++) {
msg.body.motion.pointers[i].properties.copyFrom(pointerProperties[i]);
msg.body.motion.pointers[i].coords.copyFrom(pointerCoords[i]);
}
return mChannel->sendMessage(&msg);
}
该方法所执行的操作是利用传入的触摸信息，构建点击消息，然后通过InputChannel将消息发送出去。这里引出了InputChannel，在此，我们通InputPublisher的创建反推出InputChannel是何时被引入的，何时被创建的。从而进一步分析其作用。在分析之前先让我们来对上述的分析过程做一个总结。
ReaderThread开启后会从EventHub中轮询获取时间，获取到事件之后，将进行一系列的处理，对事件进行加工包装，然后传递给相应的InputDevice，InputMapper，然后将包装的事件添加到一个事件队列中，InputDispatcher的线程则会在轮询读取该线程中的事件，然后将其再次进行做判断处理后，传递，最终到达InputChannel，通过InputChannel，来将数据发送出去。
到此，对于输入事件，我们已经分析到了InputChannel，对于其上的具体分析转化，将是接下来分析的核心。
InputChannel
从上面分析可以看到事件传递部分最后是通过InputChannel所发送出去的，那么InputChannel是在何时被创建的呢？何时被InputManager所使用的呢？同时，对于InputReaderThread和InputDispatcherThread是运行在SystemServer进程中的，而我们的应用进程是和其不在同一个进程中的。这之间一定也是有进程间的通信机制在里面。具体是如何实现的呢？这里我们从InputChannel的创建着手来看。
InputChannel的创建是在 ViewRootImpl中setView方法中。
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
....
if ((mWindowAttributes.inputFeatures
& WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {
mInputChannel = new InputChannel();
}
....
res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
getHostVisibility(), mDisplay.getDisplayId(),
mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
mAttachInfo.mOutsets, mInputChannel);
....
}
这里对于ViewRootImpl和WindowSession相关暂且不介绍，对于这方面的知识，需要很大的篇幅来介绍，这里先只是讲到是在这里创建的，对于其相关的内容将在后续的文章中介绍。这里首先是创建了一个InputChannel，然后将其调用了WindowSession的addToDisplay方法将其作为参数传递。
public InputChannel() {
}
在InputChannel中的方法都为调用了相应的native方法。这里调用的addToDisplay将会把InputChannel添加到WindowManagerService中。会调用WMS的addWindow方法。
public int addWindow(Session session, IWindow client, int seq,
WindowManager.LayoutParams attrs, int viewVisibility, int displayId,
Rect outContentInsets, Rect outStableInsets, Rect outOutsets,
InputChannel outInputChannel) {
....
final boolean openInputChannels = (outInputChannel != null
&& (attrs.inputFeatures & INPUT_FEATURE_NO_INPUT_CHANNEL) == 0);
if (openInputChannels) {
win.openInputChannel(outInputChannel);
}
....
}
对于InputChannel的相关处理调用了WindowState的openInputChannel方法。
void openInputChannel(InputChannel outInputChannel) {
if (mInputChannel != null) {
throw new IllegalStateException("Window already has an input channel.");
}
String name = makeInputChannelName();
InputChannel[] inputChannels = InputChannel.openInputChannelPair(name);
mInputChannel = inputChannels[0];
mClientChannel = inputChannels[1];
mInputWindowHandle.inputChannel = inputChannels[0];
if (outInputChannel != null) {
mClientChannel.transferTo(outInputChannel);
mClientChannel.dispose();
mClientChannel = null;
} else {
mDeadWindowEventReceiver = new DeadWindowEventReceiver(mClientChannel);
}
mService.mInputManager.registerInputChannel(mInputChannel, mInputWindowHandle);
}
首先调用了InputChannel的openInputChannelPair方法，该方法调用了InputChannel的native方法nativeOpenInputChannelPair,创建了两个InputChannel，对其中一个通过InputManager进行了InputChannel的注册。对于InputChannel的相关Native的实现是在InputTransport中，nativeOpenInputChannelPair的源码如下。
status_t InputChannel::openInputChannelPair(const String8& name,
sp<InputChannel>& outServerChannel, sp<InputChannel>& outClientChannel) {
int sockets[2];
if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sockets)) {
status_t result = -errno;
outServerChannel.clear();
outClientChannel.clear();
return result;
}
int bufferSize = SOCKET_BUFFER_SIZE;
setsockopt(sockets[0], SOL_SOCKET, SO_SNDBUF, &bufferSize, sizeof(bufferSize));
setsockopt(sockets[0], SOL_SOCKET, SO_RCVBUF, &bufferSize, sizeof(bufferSize));
setsockopt(sockets[1], SOL_SOCKET, SO_SNDBUF, &bufferSize, sizeof(bufferSize));
setsockopt(sockets[1], SOL_SOCKET, SO_RCVBUF, &bufferSize, sizeof(bufferSize));
String8 serverChannelName = name;
serverChannelName.append(" (server)");
outServerChannel = new InputChannel(serverChannelName, sockets[0]);
String8 clientChannelName = name;
clientChannelName.append(" (client)");
outClientChannel = new InputChannel(clientChannelName, sockets[1]);
return OK;
}
status_t InputChannel::sendMessage(const InputMessage* msg) {
size_t msgLength = msg->size();
ssize_t nWrite;
do {
nWrite = ::send(mFd, msg, msgLength, MSG_DONTWAIT | MSG_NOSIGNAL);
} while (nWrite == -1 && errno == EINTR);
if (nWrite < 0) {
int error = errno;
if (error == EAGAIN || error == EWOULDBLOCK) {
return WOULD_BLOCK;
}
if (error == EPIPE || error == ENOTCONN || error == ECONNREFUSED || error == ECONNRESET) {
return DEAD_OBJECT;
}
return -error;
}
if (size_t(nWrite) != msgLength) {
return DEAD_OBJECT;
}
return OK;
}
接收消息，通过读socket的方式来读取消息。
status_t InputChannel::receiveMessage(InputMessage* msg) {
ssize_t nRead;
do {
nRead = ::recv(mFd, msg, sizeof(InputMessage), MSG_DONTWAIT);
} while (nRead == -1 && errno == EINTR);
if (nRead < 0) {
int error = errno;
if (error == EAGAIN || error == EWOULDBLOCK) {
return WOULD_BLOCK;
}
if (error == EPIPE || error == ENOTCONN || error == ECONNREFUSED) {
return DEAD_OBJECT;
}
return -error;
}
if (nRead == 0) { // check for EOF
return DEAD_OBJECT;
}
if (!msg->isValid(nRead)) {
return BAD_VALUE;
}
return OK;
}
接收端的消息由谁来触发呢？是如何触发开始接受消息，消息如何在传到InputChannel之后，进行的进一步的数据传递呢？这是接下来所要去分析的，这里先对上面InputChannel进行一个总结。
之前的setView中，我们创建了InputChannel之后，开启了对于InputChannel中输入事件的监听。
if (mInputChannel != null) {
if (mInputQueueCallback != null) {
mInputQueue = new InputQueue();
mInputQueueCallback.onInputQueueCreated(mInputQueue);
}
mInputEventReceiver = new WindowInputEventReceiver(mInputChannel,
Looper.myLooper());
}
WindowInputEventReceiver的构造函数如下，其继承自InputEventReceiver。
final class WindowInputEventReceiver extends InputEventReceiver {
public WindowInputEventReceiver(InputChannel inputChannel, Looper looper) {
super(inputChannel, looper);
}
....
}
InputEventReceiver的构造函数源码如下
public InputEventReceiver(InputChannel inputChannel, Looper looper) {
....
mInputChannel = inputChannel;
mMessageQueue = looper.getQueue();
mReceiverPtr = nativeInit(new WeakReference<InputEventReceiver>(this),
inputChannel, mMessageQueue);
}
这里调用了native方法来做初始化，相关的native方法的实现在android_view_InputEventReceiver.cpp
static jlong nativeInit(JNIEnv* env, jclass clazz, jobject receiverWeak,
jobject inputChannelObj, jobject messageQueueObj) {
....
sp<InputChannel> inputChannel = android_view_InputChannel_getInputChannel(env,
inputChannelObj);
sp<MessageQueue> messageQueue = android_os_MessageQueue_getMessageQueue(env, messageQueueObj);
sp<NativeInputEventReceiver> receiver = new NativeInputEventReceiver(env,
receiverWeak, inputChannel, messageQueue);
status_t status = receiver->initialize();
.....
}
根据传入的InputChannel和MessageQueue，创建一个NativeInputEventReceiver，然后调用其initialize方法。
status_t NativeInputEventReceiver::initialize() {
setFdEvents(ALOOPER_EVENT_INPUT);
return OK;
}
在initialize()方法中，只调用了一个函数setFdEvents，
void NativeInputEventReceiver::setFdEvents(int events) {
if (mFdEvents != events) {
mFdEvents = events;
int fd = mInputConsumer.getChannel()->getFd();
if (events) {
mMessageQueue->getLooper()->addFd(fd, 0, events, this, NULL);
} else {
mMessageQueue->getLooper()->removeFd(fd);
}
}
}
从InputConsumer中获取到channel的fd，然后调用Looper的addFd方法。
int ALooper_addFd(ALooper* looper, int fd, int ident, int events,
ALooper_callbackFunc callback, void* data) {
return ALooper_to_Looper(looper)->addFd(fd, ident, events, callback, data);
}
Looper的addFd的实现如下
int Looper::addFd(int fd, int ident, int events, const sp<LooperCallback>& callback, void* data) {
Request request;
request.fd = fd;
request.ident = ident;
request.events = events;
request.seq = mNextRequestSeq++;
request.callback = callback;
request.data = data;
if (mNextRequestSeq == -1) mNextRequestSeq = 0;
struct epoll_event eventItem;
request.initEventItem(&eventItem);
ssize_t requestIndex = mRequests.indexOfKey(fd);
if (requestIndex < 0) {
int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, fd, & eventItem);
if (epollResult < 0) {
return -1;
}
mRequests.add(fd, request);
}
}
该方法所执行的操作就是对传递的fd添加epoll监控，Looper会循环调用pollOnce方法，而pollOnce方法的核心实现就是pollInner。其代码大致实现内容为等待消息的到来，当有消息到来后，根据消息类型做一些判断处理，然后调用其相关的callback。我们当前是对于开启的socket的一个监听，当有数据到来，我们便会执行相应的回调。这里对于InputChannel的回调是在调用了NativeInputEventReceiver的handleEvent方法。
int NativeInputEventReceiver::handleEvent(int receiveFd, int events, void* data) {
.....
if (events & ALOOPER_EVENT_INPUT) {
JNIEnv* env = AndroidRuntime::getJNIEnv();
status_t status = consumeEvents(env, false /*consumeBatches*/, -1, NULL);
mMessageQueue->raiseAndClearException(env, "handleReceiveCallback");
return status == OK || status == NO_MEMORY ? 1 : 0;
}
....
return 1;
}
对于Event的处理，这里调用consumeEvents来对事件进行处理。
status_t NativeInputEventReceiver::consumeEvents(JNIEnv* env,
bool consumeBatches, nsecs_t frameTime, bool* outConsumedBatch) {
...
for(;;) {
...
InputEvent* inputEvent;
status_t status = mInputConsumer.consume(&mInputEventFactory,
consumeBatches, frameTime, &seq, &inputEvent);
...
}
...
}
InputConsumer是在InputTransport中做的声明。
status_t InputConsumer::consume(InputEventFactoryInterface* factory,
bool consumeBatches, nsecs_t frameTime, uint32_t* outSeq, InputEvent** outEvent) {
while (!*outEvent) {
....
status_t result = mChannel->receiveMessage(&mMsg);
....
}
}
调用consume方法会持续的调用InputChannel的receiveMessage方法来从socket中读取数据。到这里，我们已经将写入socket的事件读出来了。
public void registerInputChannel(InputChannel inputChannel,
InputWindowHandle inputWindowHandle) {
if (inputChannel == null) {
throw new IllegalArgumentException("inputChannel must not be null.");
}
nativeRegisterInputChannel(mPtr, inputChannel, inputWindowHandle, false);
}
nativeRegisterInputManger
static void nativeRegisterInputChannel(JNIEnv* env, jclass /* clazz */,
jlong ptr, jobject inputChannelObj, jobject inputWindowHandleObj, jboolean monitor) {
NativeInputManager* im = reinterpret_cast<NativeInputManager*>(ptr);
sp<InputChannel> inputChannel = android_view_InputChannel_getInputChannel(env,
inputChannelObj);
if (inputChannel == NULL) {
throwInputChannelNotInitialized(env);
return;
}
sp<InputWindowHandle> inputWindowHandle =
android_server_InputWindowHandle_getHandle(env, inputWindowHandleObj);
status_t status = im->registerInputChannel(
env, inputChannel, inputWindowHandle, monitor);
if (status) {
String8 message;
message.appendFormat("Failed to register input channel. status=%d", status);
jniThrowRuntimeException(env, message.string());
return;
}
if (! monitor) {
android_view_InputChannel_setDisposeCallback(env, inputChannelObj,
handleInputChannelDisposed, im);
}
}
NativeInputManager的registerInputChannel还会调用到InputDispatcher的registerInputChannel，会通过InputChannel创建相应的Connection，同时将InputChannel加入到相应的监控之中。在上面对代码的分析之中，获取InputChannel，就是通过这个Connection来获取的。
status_t InputDispatcher::registerInputChannel(const sp<InputChannel>& inputChannel,
const sp<InputWindowHandle>& inputWindowHandle, bool monitor) {
{ // acquire lock
AutoMutex _l(mLock);
if (getConnectionIndexLocked(inputChannel) >= 0) {
return BAD_VALUE;
}
sp<Connection> connection = new Connection(inputChannel, inputWindowHandle, monitor);
int fd = inputChannel->getFd();
mConnectionsByFd.add(fd, connection);
if (monitor) {
mMonitoringChannels.push(inputChannel);
}
mLooper->addFd(fd, 0, ALOOPER_EVENT_INPUT, handleReceiveCallback, this);
} // release lock
// Wake the looper because some connections have changed.
mLooper->wake();
return OK;
}
ViewRootImpl
事件在从socket读出之后，经过传递，最终会调用到ViewRootImpl的enqueueInputEvent方法。
void enqueueInputEvent(InputEvent event,
InputEventReceiver receiver, int flags, boolean processImmediately) {
adjustInputEventForCompatibility(event);
QueuedInputEvent q = obtainQueuedInputEvent(event, receiver, flags);
QueuedInputEvent last = mPendingInputEventTail;
if (last == null) {
mPendingInputEventHead = q;
mPendingInputEventTail = q;
} else {
last.mNext = q;
mPendingInputEventTail = q;
}
mPendingInputEventCount += 1;
if (processImmediately) {
doProcessInputEvents();
} else {
scheduleProcessInputEvents();
}
}
enqueueInputEvent方法从InputEventReceiver中获取到InputEvent，然后将其加入到当前的事件队列之中，最后调用doProcessInputEvents来进行处理。
void doProcessInputEvents() {
while (mPendingInputEventHead != null) {
QueuedInputEvent q = mPendingInputEventHead;
mPendingInputEventHead = q.mNext;
if (mPendingInputEventHead == null) {
mPendingInputEventTail = null;
}
q.mNext = null;
mPendingInputEventCount -= 1;
long eventTime = q.mEvent.getEventTimeNano();
long oldestEventTime = eventTime;
if (q.mEvent instanceof MotionEvent) {
MotionEvent me = (MotionEvent)q.mEvent;
if (me.getHistorySize() > 0) {
oldestEventTime = me.getHistoricalEventTimeNano(0);
}
}
mChoreographer.mFrameInfo.updateInputEventTime(eventTime, oldestEventTime);
deliverInputEvent(q);
}
// We are done processing all input events that we can process right now
// so we can clear the pending flag immediately.
if (mProcessInputEventsScheduled) {
mProcessInputEventsScheduled = false;
mHandler.removeMessages(MSG_PROCESS_INPUT_EVENTS);
}
}
遍历所有的消息，如果事件类型为触摸屏事件，对其进行相应的时间修改，最后对于每一个处理完成的事件调用deliverInputEvent,
private void deliverInputEvent(QueuedInputEvent q) {
q.mEvent.getSequenceNumber());
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onInputEvent(q.mEvent, 0);
}
InputStage stage;
if (q.shouldSendToSynthesizer()) {
stage = mSyntheticInputStage;
} else {
stage = q.shouldSkipIme() ? mFirstPostImeInputStage : mFirstInputStage;
}
if (stage != null) {
stage.deliver(q);
} else {
finishInputEvent(q);
}
}
在事件分发环节，首先进行事件的一个判断，通过shouldSkipIme来判断是否传递给输入法，然后决定使用何种InputStage进行消息的继续传递，这里实现了多种InputStage，对于每一个类型的InputStage都实现了一个方法process方法来针对不同类型的事件做处理，如果是触摸屏类的消息，最终会将事件的处理转交到View的身上。
InputStage中的事件如何传递处理，传递处理之后，如何进行
对于InputStage涉及的篇幅较多，这里也不再展开，当消息到达ViewRootImpl中后，接下来就是在View间的派发。
View的事件派发
对于View层的事件派发，我们最常见的就是dispatchTouchEvent，onTouch,onInterceptTouchEvent,onClick，onTouchEvent等。对于View树上事件的派发，就是在对树的遍历传递中，主要起作用的就是这几个函数。这里我们先从View的相关事件函数开始分析，由于ViewGroup具有子View的原因，其相关的事件派发逻辑和View有所区别，这里我们先进行View的事件分析。
public boolean dispatchTouchEvent(MotionEvent event) {
....
if (onFilterTouchEventForSecurity(event)) {
if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {
result = true;
}
//noinspection SimplifiableIfStatement
ListenerInfo li = mListenerInfo;
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
result = true;
}
if (!result && onTouchEvent(event)) {
result = true;
}
}
....
return result；
}
对于在View上的事件派发，核心操作是两点，一个是调用监听器的onTouch方法，然后判断事件是否被消耗，如果没有被消耗，则会调用onTouchEvent方法。在onTouchEvent中根据消息类型进行一些处理。
根据事件类型来更新内部的一些状态。这里比较复杂的还是在ViewGroup中的事件分发逻辑，这里在分发的过程中，需要判断是否对事件进行拦截，如果不拦截，是否自身可处理，如果需要考虑到其中的子View。这里对其中的关键代码进行逐步分析。
final boolean intercepted;
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
if (!disallowIntercept) {
intercepted = onInterceptTouchEvent(ev);
ev.setAction(action); // restore action in case it was changed
} else {
intercepted = false;
}
} else {
intercepted = true;
}
判断是否进行拦截，调用自身的onInterceptTouchEvent，开发者可以重载这个方法进行自己的一些操作。返回true表示拦截事件。如果要对事件进行拦截，则不再进行子View的遍历。否则将会进行子View的遍历，事件传递，在子View的事件传递结束之后，如果子View将事件消耗了则会将其加入到mFirstTouchTarget，如果遍历完成没有任何被添加
if (mFirstTouchTarget == null) {
// No touch targets so treat this as an ordinary view.
handled = dispatchTransformedTouchEvent(ev, canceled, null,
TouchTarget.ALL_POINTER_IDS);
}
接下来进行的是对于事件在子View中的派发，这里我们也只是针对其中的核心代码进行分析。
final View[] children = mChildren;
for (int i = childrenCount - 1; i >= 0; i--) {
final int childIndex = getAndVerifyPreorderedIndex(
childrenCount, i, customOrder);
final View child = getAndVerifyPreorderedView(
preorderedList, children, childIndex);
....
dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign);
....
}
在对子View进行遍历的处理的时候，如果子View的事件被消耗，那么我们就会将其TouchTarget赋值给mFirstTouchTarget，当检测到mFirstTouchTarget为空时会再调用Viewgroup自身的dispatchTransformedTouchEvent方法，这个时候就会调用其onTouchEvent，然后继续View中的事件传递流程。
if (mFirstTouchTarget == null) {
// No touch targets so treat this as an ordinary view.
handled = dispatchTransformedTouchEvent(ev, canceled, null,
TouchTarget.ALL_POINTER_IDS);
}
对于dispatchTransformedTouchEvent函数
private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,
View child, int desiredPointerIdBits) {
if (cancel || oldAction == MotionEvent.ACTION_CANCEL) {
event.setAction(MotionEvent.ACTION_CANCEL);
if (child == null) {
handled = super.dispatchTouchEvent(event);
} else {
handled = child.dispatchTouchEvent(event);
}
event.setAction(oldAction);
return handled;
}
....
}
这里事件的派发也是在调用了每一个子View的dispatchTouchEvent方法，根据返回结果来判断是否被消耗，一旦事件被消耗则会停止传递。
