事件处理机制(一)
2021-09-27 本文已影响0人
涛涛123759
一、事件接收流程
首先我们在ViewRootImpl#setView创建View的接收事件
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView, int userId) {
...
if (inputChannel != null) {
if (mInputQueueCallback != null) {
mInputQueue = new InputQueue();
mInputQueueCallback.onInputQueueCreated(mInputQueue);
}
//接收事件
mInputEventReceiver = new WindowInputEventReceiver(inputChannel,
Looper.myLooper());
}
...
}
然后我们看ViewRootImpl的内部类WindowInputEventReceiver
final class WindowInputEventReceiver extends InputEventReceiver {
public WindowInputEventReceiver(InputChannel inputChannel, Looper looper) {
super(inputChannel, looper);
}
@Override
public void onInputEvent(InputEvent event) {
Trace.traceBegin(Trace.TRACE_TAG_VIEW, "processInputEventForCompatibility");
List<InputEvent> processedEvents;
try {
processedEvents =
mInputCompatProcessor.processInputEventForCompatibility(event);
} finally {
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
}
if (processedEvents != null) {
if (processedEvents.isEmpty()) {
// InputEvent consumed by mInputCompatProcessor
finishInputEvent(event, true);
} else {
for (int i = 0; i < processedEvents.size(); i++) {
//派发事件
enqueueInputEvent(
processedEvents.get(i), this,
QueuedInputEvent.FLAG_MODIFIED_FOR_COMPATIBILITY, true);
}
}
} else {
enqueueInputEvent(event, this, 0, true);
}
}
@Override
public void onBatchedInputEventPending(int source) {
// mStopped: There will be no more choreographer callbacks if we are stopped,
// so we must consume all input immediately to prevent ANR
final boolean unbuffered = mUnbufferedInputDispatch
|| (source & mUnbufferedInputSource) != SOURCE_CLASS_NONE
|| mStopped;
if (unbuffered) {
if (mConsumeBatchedInputScheduled) {
unscheduleConsumeBatchedInput();
}
// Consume event immediately if unbuffered input dispatch has been requested.
consumeBatchedInputEvents(-1);
return;
}
scheduleConsumeBatchedInput();
}
@Override
public void onFocusEvent(boolean hasFocus, boolean inTouchMode) {
windowFocusChanged(hasFocus, inTouchMode);
}
@Override
public void dispose() {
unscheduleConsumeBatchedInput();
super.dispose();
}
}
WindowInputEventReceiver mInputEventReceiver;
然后在onInputEvent中调用enqueueInputEvent获取事件
void enqueueInputEvent(InputEvent event,
InputEventReceiver receiver, int flags, boolean processImmediately) {
QueuedInputEvent q = obtainQueuedInputEvent(event, receiver, flags);
// the time stamp of injected events are monotonic.
QueuedInputEvent last = mPendingInputEventTail;
if (last == null) {
mPendingInputEventHead = q;
mPendingInputEventTail = q;
} else {
last.mNext = q;
mPendingInputEventTail = q;
}
mPendingInputEventCount += 1;
Trace.traceCounter(Trace.TRACE_TAG_INPUT, mPendingInputEventQueueLengthCounterName,
mPendingInputEventCount);
if (processImmediately) {
doProcessInputEvents();
} else {
scheduleProcessInputEvents();
}
}
void doProcessInputEvents() {
// Deliver all pending input events in the queue.
while (mPendingInputEventHead != null) {
QueuedInputEvent q = mPendingInputEventHead;
mPendingInputEventHead = q.mNext;
if (mPendingInputEventHead == null) {
mPendingInputEventTail = null;
}
q.mNext = null;
mPendingInputEventCount -= 1;
Trace.traceCounter(Trace.TRACE_TAG_INPUT, mPendingInputEventQueueLengthCounterName,
mPendingInputEventCount);
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);
//处理事件
deliverInputEvent(q);
}
// so we can clear the pending flag immediately.
if (mProcessInputEventsScheduled) {
mProcessInputEventsScheduled = false;
//移出事件
mHandler.removeMessages(MSG_PROCESS_INPUT_EVENTS);
}
}
private void deliverInputEvent(QueuedInputEvent q) {
...
InputStage stage;
if (q.shouldSendToSynthesizer()) {
stage = mSyntheticInputStage;
} else {
stage = q.shouldSkipIme() ? mFirstPostImeInputStage : mFirstInputStage;
}
if (stage != null) {
handleWindowFocusChanged();
//处理事件
stage.deliver(q);
} else {
//结束事件
finishInputEvent(q);
}
}
在这个方法中调用InputStage的各个方法deliver， 处理完事件后就会finishInputEvent来完成事件分发操作。
1.1、各个InputStage
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView, int userId) {
mSyntheticInputStage = new SyntheticInputStage();
InputStage viewPostImeStage = new ViewPostImeInputStage(mSyntheticInputStage);
InputStage nativePostImeStage = new NativePostImeInputStage(viewPostImeStage,
"aq:native-post-ime:" + counterSuffix);
InputStage earlyPostImeStage = new EarlyPostImeInputStage(nativePostImeStage);
InputStage imeStage = new ImeInputStage(earlyPostImeStage,
"aq:ime:" + counterSuffix);
InputStage viewPreImeStage = new ViewPreImeInputStage(imeStage);
InputStage nativePreImeStage = new NativePreImeInputStage(viewPreImeStage,
"aq:native-pre-ime:" + counterSuffix);
}
构造了7个InputStage实现类，
NativePreImeInputStage: 主要是为了将消息放到NativeActivity中去处理, NativeActivity和普通Acitivty的功能区别不大,只是很多代码都在native层去实现,这样执行效率更高,并且NativeActivity在游戏开发中很实用。ViewPreImeInputStage: 从名字中就可得知,最后会调用Acitivity的所有view的onkeyPreIme方法,这样就给View在输入法处理key事件之前先得到消息并处理的机会。ImeInputStage: ImeInputStage的onProcess方法会调用InputMethodManager的dispatchInputEvent方法处理消息。EarlyPostImeInputStage: 屏幕上有焦点的View会高亮显示,用来提示用户焦点所在。NativePostImeInputStage: 为了让IME处理完消息后能先于普通的Activity处理消息。ViewPostImeInputStage: Acitivity和view处理各种消息。SyntheticInputStage: 流水线的最后一级,经过层层过滤之后,到达这里的消息已经不多了,例如手机上的虚拟按键消息。
那么Activity和View的事件处理主要对应的InputStage是ViewPostImeInputStage。
1.2、ViewPostImeInputStage
调用ViewPostImeInputStage的父类InputStage#deliver方法
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);
}
}
protected int onProcess(QueuedInputEvent q) {
return FORWARD;
}
}
接下来看 ViewPostImeInputStage的onProcess方法
final class ViewPostImeInputStage extends InputStage {
public ViewPostImeInputStage(InputStage next) {
super(next);
}
@Override
protected int onProcess(QueuedInputEvent q) {
if (q.mEvent instanceof KeyEvent) {
return processKeyEvent(q);
} else {
final int source = q.mEvent.getSource();
if ((source & InputDevice.SOURCE_CLASS_POINTER) != 0) {
//处理点击事件
return processPointerEvent(q);
} else if ((source & InputDevice.SOURCE_CLASS_TRACKBALL) != 0) {
return processTrackballEvent(q);
} else {
return processGenericMotionEvent(q);
}
}
}
}
private int processPointerEvent(QueuedInputEvent q) {
final MotionEvent event = (MotionEvent) q.mEvent;
mAttachInfo.mUnbufferedDispatchRequested = false;
mAttachInfo.mHandlingPointerEvent = true;
//mView ==> DecorView
boolean handled = mView.dispatchPointerEvent(event);
maybeUpdatePointerIcon(event);
maybeUpdateTooltip(event);
mAttachInfo.mHandlingPointerEvent = false;
if (mAttachInfo.mUnbufferedDispatchRequested && !mUnbufferedInputDispatch) {
mUnbufferedInputDispatch = true;
if (mConsumeBatchedInputScheduled) {
scheduleConsumeBatchedInputImmediately();
}
}
return handled ? FINISH_HANDLED : FORWARD;
}
会调用到DecorView 的 dispatchTouchEvent
二、View继承关系调用
2.1、我们先看DecorView 的继承关系
private final class DecorView extends FrameLayout implements RootViewSurfaceTaker{...}
public class FrameLayout extends ViewGroup {...}
public abstract class ViewGroup extends View implements ViewParent, ViewManager{..}
2.2、事件处理
最后回调到父类View的dispatchPointerEvent
public final boolean dispatchPointerEvent(MotionEvent event) {
if (event.isTouchEvent()) {
//分发事件
return dispatchTouchEvent(event);
} else {
return dispatchGenericMotionEvent(event);
}
}
然后再回到顶层DecorView中执行dispatchTouchEvent
public boolean dispatchTouchEvent(MotionEvent ev) {
//cb==> Activity
final Window.Callback cb = mWindow.getCallback();
//mWindow ==> PhoneWindow
return cb != null && !mWindow.isDestroyed() && mFeatureId < 0
? cb.dispatchTouchEvent(ev) : super.dispatchTouchEvent(ev);
}
调用Activity的dispatchTouchEvent，先调用各个DispatchTouchEvent，最后才调用 onTouchEvent。因此最早 dispatchTouchEvent，应用最晚 onTouchEvent。
public boolean dispatchTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
onUserInteraction();
}
//getWindow()获取的是PhoneWindow，子View 处理
if (getWindow().superDispatchTouchEvent(ev)) {
return true;
}
//如果子View都不处理，自己处理事件
return onTouchEvent(ev);
}
调用PhoneWindow#superDispatchTouchEvent
public boolean superDispatchTouchEvent(MotionEvent event) {
//mDecor ==> DecorView
return mDecor.superDispatchTouchEvent(event);
}
调用DecorView#superDispatchTouchEvent
public boolean superDispatchTouchEvent(MotionEvent event) {
return super.dispatchTouchEvent(event);
}
调用ViewGoup#superDispatchTouchEvent
public boolean dispatchTouchEvent(MotionEvent ev) {
...
}
private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,
View child, int desiredPointerIdBits) {
final boolean handled;
...
// Perform any necessary transformations and dispatch.
if (child == null) {
handled = super.dispatchTouchEvent(transformedEvent);
} else {
final float offsetX = mScrollX - child.mLeft;
final float offsetY = mScrollY - child.mTop;
transformedEvent.offsetLocation(offsetX, offsetY);
if (! child.hasIdentityMatrix()) {
transformedEvent.transform(child.getInverseMatrix());
}
handled = child.dispatchTouchEvent(transformedEvent);
}
最后调用View#dispatchTouchEvent
public boolean dispatchTouchEvent(MotionEvent event) { ... }
在调用 onTouchEvent处理事件
public boolean onTouchEvent(MotionEvent event) { ... }
事件种类
具体事件怎么处理见下章
