InputChannel发送Input给App-Android12

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InputChannel发送Input给App-Android12

android12-release

1. App的ViewRootImpl建立InputChannel

查看 InputChannel通道建立-Android12 1. APP界面建立InputChannel，下面看图：

InputChannel / WindowInputEventReceiver建立联系，并建立服务端Connection
InputStage责任链：SyntheticInputStage - ViewPostImeInputStage - NativePostImeInputStage - EarlyPostImeInputStage - ImeInputStage - ViewPreImeInputStage - NativePreImeInputStage

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2. InputChannel通过socket发送Input给App

2.1 InputChannel通过socket发送

查看 InputDispatcher线程分发事件-Android12 ，InputPublisher::publishKeyEvent通过mChannel->sendMessage(&msg)发送

nWrite = ::send(getFd(), &cleanMsg, msgLength, MSG_DONTWAIT | MSG_NOSIGNAL)目标Fd写入

frameworks/native/libs/input/InputTransport.cpp

status_t InputChannel::sendMessage(const InputMessage* msg) {const size_t msgLength = msg->size();InputMessage cleanMsg;msg->getSanitizedCopy(&cleanMsg);ssize_t nWrite;do {nWrite = ::send(getFd(), &cleanMsg, msgLength, MSG_DONTWAIT | MSG_NOSIGNAL);} while (nWrite == -1 && errno == EINTR);if (nWrite < 0) {int error = errno;
#if DEBUG_CHANNEL_MESSAGESALOGD("channel '%s' ~ error sending message of type %d, %s", mName.c_str(),msg->header.type, strerror(error));
#endifif (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) {
#if DEBUG_CHANNEL_MESSAGESALOGD("channel '%s' ~ error sending message type %d, send was incomplete",mName.c_str(), msg->header.type);
#endifreturn DEAD_OBJECT;}#if DEBUG_CHANNEL_MESSAGESALOGD("channel '%s' ~ sent message of type %d", mName.c_str(), msg->header.type);
#endifreturn OK;
}

2.2 WindowInputEventReceiver接收input消息

WindowInputEventReceiver中LooperCallback回调handleEvent()在android_view_InputEventReceiver.cpp中，最终调用到WindowInputEventReceiver.onInputEvent：NativeInputEventReceiver::handleEvent -- consumeEvents -- gInputEventReceiverClassInfo.dispatchInputEvent -> InputEventReceiver.onInputEvent(event) -> WindowInputEventReceiver.onInputEvent

frameworks/base/core/java/android/view/InputEventReceiver.java
frameworks/base/core/jni/android_view_InputEventReceiver.cpp
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2.3 ViewRootImpl中执行InputStage 责任链

通过enqueueInputEvent -> doProcessInputEvents -> deliverInputEvent -> stage.deliver(q)调用执行InputStage 责任链
InputStage的各子类Input事件result = onProcess(q)处理，再判断是forward()向下传递，还是finish()结束

abstract class InputStage {// ... ...public final void deliver(QueuedInputEvent q) {if ((q.mFlags & QueuedInputEvent.FLAG_FINISHED) != 0) {forward(q);} else if (shouldDropInputEvent(q)) {finish(q, false);} else {traceEvent(q, Trace.TRACE_TAG_VIEW);final int result;try {result = onProcess(q);} finally {Trace.traceEnd(Trace.TRACE_TAG_VIEW);}apply(q, result);}}/*** Marks the the input event as finished then forwards it to the next stage.*/protected void finish(QueuedInputEvent q, boolean handled) {q.mFlags |= QueuedInputEvent.FLAG_FINISHED;if (handled) {q.mFlags |= QueuedInputEvent.FLAG_FINISHED_HANDLED;}forward(q);}/*** Forwards the event to the next stage.*/protected void forward(QueuedInputEvent q) {onDeliverToNext(q);}/*** Applies a result code from {@link #onProcess} to the specified event.*/protected void apply(QueuedInputEvent q, int result) {if (result == FORWARD) {forward(q);} else if (result == FINISH_HANDLED) {finish(q, true);} else if (result == FINISH_NOT_HANDLED) {finish(q, false);} else {throw new IllegalArgumentException("Invalid result: " + result);}}/*** Called when an event is ready to be processed.* @return A result code indicating how the event was handled.*/protected int onProcess(QueuedInputEvent q) {return FORWARD;}/*** Called when an event is being delivered to the next stage.*/protected void onDeliverToNext(QueuedInputEvent q) {if (DEBUG_INPUT_STAGES) {Log.v(mTag, "Done with " + getClass().getSimpleName() + ". " + q);}if (mNext != null) {mNext.deliver(q);} else {finishInputEvent(q);}}// ... ...
}

3. 例如ViewPostImeInputStage中processKeyEvent

关注KeyEvent事件分发给APP界面窗口。mView就是App的RootViewImpl.setView设置，涉及PhoneWindow.java、DecorView.java，查看DecorView.dispatchKeyEvent 最终会分发到真正需要处理该时间的窗口。这里handled可以判断应用是否拦截KeyEvent事件，但是需要明白的是不管应用拦不拦截，Input事件都已经发送给应用了。
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