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.cpp
void 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。