从点击屏幕到事件处理的事件分发源码流程
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2022-05-14 15:47:33
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从点击屏幕到事件处理的事件分发源码流程
有事没事先来张图
怎么打印出来的，代码先奉上
Thread.dumpStack();
在dispatchTouchEvent(MotionEvent event)方法中执行该方法
通过以上方法，可打印出从点击屏幕到执行dispatchTouchEvent(MotionEvent event)的执行流程，感觉以后分析再也不用去一个个方法去找了直接根据流程来就是了
欢迎底层大佬打脸底层萌新的我
第一个执行是ZygoteInit的main()方法感觉回到了最初学java的时候了，原来android系统也是从从main方法开始的啊
一直觉得android世界里没有main方法的呢
ZygoteInit
public static void main(String argv[]) {
try {
...
} catch (MethodAndArgsCaller caller) {
caller.run();
} catch (RuntimeException ex) {
closeServerSocket();
throw ex;
}
}
底层的东西不敢说话，咱们直接看流程
ZygoteInit$MethodAndArgsCaller.run
public void run() {
try {
mMethod.invoke(null, new Object[] { mArgs });
} catch (IllegalAccessException ex) {
throw new RuntimeException(ex);
} catch (InvocationTargetException ex) {
Throwable cause = ex.getCause();
if (cause instanceof RuntimeException) {
throw (RuntimeException) cause;
} else if (cause instanceof Error) {
throw (Error) cause;
}
throw new RuntimeException(ex);
}
}
这里执行了mMethod方法，这个mMethod通过构造方法传递赋值
new ZygoteInit.MethodAndArgsCaller(m, argv);
Method m;
try {
m = cl.getMethod("main", new Class[] { String[].class });
} catch (NoSuchMethodException ex) {
throw new RuntimeException(
"Missing static main on " + className, ex);
} catch (SecurityException ex) {
throw new RuntimeException(
"Problem getting static main on " + className, ex);
}
这里的mThread执行了main方法，这个main方法是ActivityThread的main方法
ActivityThread
public static void main(String[] args) {
SamplingProfilerIntegration.start();
CloseGuard.setEnabled(false);
Environment.initForCurrentUser();
EventLogger.setReporter(new EventLoggingReporter());
Security.addProvider(new AndroidKeyStoreProvider());
Process.setArgV0("<pre-initialized>");
//mainThread都不用自己prepare()
Looper.prepareMainLooper();
//居然新建自己
ActivityThread thread = new ActivityThread();
thread.attach(false);
if (sMainThreadHandler == null) {
sMainThreadHandler = thread.getHandler();
}
AsyncTask.init();
if (false) {
Looper.myLooper().setMessageLogging(new
LogPrinter(Log.DEBUG, "ActivityThread"));
}
//handler的looper循环
Looper.loop();
throw new RuntimeException("Main thread loop unexpectedly exited");
}
接下里是MessageQueue的执行，然后执行dispatchInputEvent()
InputEventReceiver
// Called from native code.
private void dispatchInputEvent(int seq, InputEvent event) {
mSeqMap.put(event.getSequenceNumber(), seq);
onInputEvent(event);
}
这就是底层里出来的方法，终于顺眼了
这个方法是处理分发输入事件的
public void onInputEvent(InputEvent event) {
finishInputEvent(event, false);
}
这里有输入事件时这个方法会被调用，这里不会执行finishInputEvent()方法，而执行ViewRootImpl中的
WindowInputEventReceiver类的onInputEvent();
WindowInputEventReceiver继承了上面的InputEventReceiver
ViewRootImpl$WindowInputEventReceiver
final class WindowInputEventReceiver extends InputEventReceiver {
public WindowInputEventReceiver(InputChannel inputChannel, Looper looper) {
super(inputChannel, looper);
}
@Override
public void onInputEvent(InputEvent event) {
enqueueInputEvent(event, this, 0, true);
}
@Override
public void onBatchedInputEventPending() {
scheduleConsumeBatchedInput();
}
@Override
public void dispose() {
unscheduleConsumeBatchedInput();
super.dispose();
}
}
接着执行enqueueInpoutEvent()
ViewRootImpl
void enqueueInputEvent(InputEvent event,
InputEventReceiver receiver, int flags, boolean processImmediately) {
QueuedInputEvent q = obtainQueuedInputEvent(event, receiver, flags);
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);
//是否立即执行
if (processImmediately) {
doProcessInputEvents();
} else {
scheduleProcessInputEvents();
}
}
接着doProcessInputEvents();
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);
//交付处理输入事件
deliverInputEvent(q);
}
// 完成了所有输入事件的处理清除标志
if (mProcessInputEventsScheduled) {
mProcessInputEventsScheduled = false;
mHandler.removeMessages(MSG_PROCESS_INPUT_EVENTS);
}
}
接着deliverInputEvent();
private void deliverInputEvent(QueuedInputEvent q) {
Trace.traceBegin(Trace.TRACE_TAG_VIEW, "deliverInputEvent");
try {
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onInputEvent(q.mEvent, 0);
}
//处理输入事件的阶段基类
InputStage stage = q.shouldSkipIme() ? mFirstPostImeInputStage : mFirstInputStage;
if (stage != null) {
//输入阶段交付处理
stage.deliver(q);
} else {
finishInputEvent(q);
}
} finally {
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
}
}
ViewRootImpl$InputStage
//交付要处理的事件
public final void deliver(QueuedInputEvent q) {
if ((q.mFlags & QueuedInputEvent.FLAG_FINISHED) != 0) {
forward(q);
} else if (shouldDropInputEvent(q)) {
finish(q, false);
} else {
apply(q, onProcess(q));
}
}
接着apply()；
//将事件应用到指定的事件
protected void apply(QueuedInputEvent q, int result) {
if (result == FORWARD) {
forward(q);
} else if (result == FINISH_HANDLED) {
finish(q, true);
} else if (result == FINISH_NOT_HANDLED) {
finish(q, false);
} else {
throw new IllegalArgumentException("Invalid result: " + result);
}
}
接着forward(q)；
//将事件向下一阶段抛出
protected void forward(QueuedInputEvent q) {
onDeliverToNext(q);
}
接着onDeliverToNext（）；
protected void onDeliverToNext(QueuedInputEvent q) {
if (mNext != null) {
//下一阶段接着处理
mNext.deliver(q);
} else {
finishInputEvent(q);
}
}
接着又交付处理deliver(q)，执行apply()方法，这里的apply()是子类的方法
ViewRootImpl$AsyncInputStage
AsyncInputStage可实现异步处理事件也是顺序处理阶段的基类
@Override
protected void apply(QueuedInputEvent q, int result) {
if (result == DEFER) {
defer(q);
} else {
super.apply(q, result);
}
}
接着又执行父类的apply方法即InputStage的apply（），又执行AsyncInputStage的forward（）
@Override
protected void forward(QueuedInputEvent q) {
//清除延迟标志
q.mFlags &= ~QueuedInputEvent.FLAG_DEFERRED;
// 如果队列为空，则重来
QueuedInputEvent curr = mQueueHead;
if (curr == null) {
super.forward(q);
return;
}
// 确定事件在传递到下一阶段之前是否进行序列化
final int deviceId = q.mEvent.getDeviceId();
QueuedInputEvent prev = null;
boolean blocked = false;
while (curr != null && curr != q) {
if (!blocked && deviceId == curr.mEvent.getDeviceId()) {
blocked = true;
}
prev = curr;
curr = curr.mNext;
}
//如果阻塞了会放到队列中稍后处理，如果延迟了也可能没有放入队列中
if (blocked) {
if (curr == null) {
enqueue(q);
}
return;
}
//事件没有阻止立即移交处理
if (curr != null) {
curr = curr.mNext;
dequeue(q, prev);
}
super.forward(q);
while (curr != null) {
if (deviceId == curr.mEvent.getDeviceId()) {
if ((curr.mFlags & QueuedInputEvent.FLAG_DEFERRED) != 0) {
break;
}
QueuedInputEvent next = curr.mNext;
dequeue(curr, prev);
super.forward(curr);
curr = next;
} else {
prev = curr;
curr = curr.mNext;
}
}
}
接着执行了父类的forward()方法，接着顺讯执行了父类的onDeliverToNext()、deliver(),最后执行ViewPostImeInputStage.onProcess(),ViewPostImeInputStage也继承了InputStage
ViewRootImpl$ViewPostImeInputStage
@Override
protected int onProcess(QueuedInputEvent q) {
if (q.mEvent instanceof KeyEvent) {
return processKeyEvent(q);
} else {
//如果交付了一个新的非键事件，确保window现在允许更新
handleDispatchDoneAnimating();
final int source = q.mEvent.getSource();
if ((source & InputDevice.SOURCE_CLASS_POINTER) != 0) {
return processPointerEvent(q);
} else if ((source & InputDevice.SOURCE_CLASS_TRACKBALL) != 0) {
return processTrackballEvent(q);
} else {
return processGenericMotionEvent(q);
}
}
}
接着processPointerEvent(q)开始处理事件分发了
private int processPointerEvent(QueuedInputEvent q) {
final MotionEvent event = (MotionEvent)q.mEvent;
//这里的mView就是decorView，在ViewRootImpl中的setView中被赋值，
//了解源码知道在Activity的makeVisible方法系列流程中在windowMangerGlobal中会new ViewRootImpl并会调用setView方法
if (mView.dispatchPointerEvent(event)) {
return FINISH_HANDLED;
}
return FORWARD;
}
接着执行View的dispatchPointerEvent()
View
public final boolean dispatchPointerEvent(MotionEvent event) {
//是否触摸事件
if (event.isTouchEvent()) {
return dispatchTouchEvent(event);
} else {
return dispatchGenericMotionEvent(event);
}
}
接下里执行的decorView的dispatchTouchEvent()
PhoneWindow$DecorView
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
//这执行了回调的dispatchTouchEvent()
final Callback cb = getCallback();
return cb != null && !isDestroyed() && mFeatureId < 0 ? cb.dispatchTouchEvent(ev)
: super.dispatchTouchEvent(ev);
}
这里的CallBack是Window的Callback接口，而Activitiy实现了Window的Callback接口，这个cb.dispatchTouchEvent()也就执行了Activity的dispatchTouchEvent()
Activity
//这个也就我们在activity中使用的dispatchTouchEveent()
public boolean dispatchTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
onUserInteraction();
}
if (getWindow().superDispatchTouchEvent(ev)) {
return true;
}
return onTouchEvent(ev);
}
接着执行了getWindow().superDispatchTouchEvent()
window是一个接口，它的实现类是PhoneWindow
PhoneWindow
@Override
public boolean superDispatchTouchEvent(MotionEvent event) {
//又交给了decorView
return mDecor.superDispatchTouchEvent(event);
}
PhoneWindw$DecorView
public boolean superDispatchTouchEvent(MotionEvent event) {
return super.dispatchTouchEvent(event);
}
ViewGroup
//处理事件的分发
public boolean dispatchTouchEvent(MotionEvent event) {
//检查触摸事件
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onTouchEvent(event, 0);
}
if (onFilterTouchEventForSecurity(event)) {
//noinspection SimplifiableIfStatement
ListenerInfo li = mListenerInfo;
//onTouchListener级别高于onTouchEvent()
if (li != null && li.mOnTouchListener != null && (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
return true;
}
if (onTouchEvent(event)) {
return true;
}
}
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onUnhandledEvent(event, 0);
}
return false;
接着dispatchTransformedTouchEvent()
private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,
View child, int desiredPointerIdBits) {
final boolean handled;
// 获取动作，重要的是动作，不是内容
final int oldAction = event.getAction();
if (cancel || oldAction == MotionEvent.ACTION_CANCEL) {
event.setAction(MotionEvent.ACTION_CANCEL);
//如果子类为空，执行父类的dispatchhTouchEvent
if (child == null) {
handled = super.dispatchTouchEvent(event);
} else {
不为空执行子类的
handled = child.dispatchTouchEvent(event);
}
event.setAction(oldAction);
return handled;
}
final int oldPointerIdBits = event.getPointerIdBits();
final int newPointerIdBits = oldPointerIdBits & desiredPointerIdBits;
//由于某些原因事件没有pointer
if (newPointerIdBits == 0) {
return false;
}
final MotionEvent transformedEvent;
if (newPointerIdBits == oldPointerIdBits) {
if (child == null || child.hasIdentityMatrix()) {
if (child == null) {
handled = super.dispatchTouchEvent(event);
} else {
final float offsetX = mScrollX - child.mLeft;
final float offsetY = mScrollY - child.mTop;
event.offsetLocation(offsetX, offsetY);
handled = child.dispatchTouchEvent(event);
event.offsetLocation(-offsetX, -offsetY);
}
return handled;
}
transformedEvent = MotionEvent.obtain(event);
} else {
transformedEvent = event.split(newPointerIdBits);
}
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);
}
transformedEvent.recycle();
return handled;
}
流程到这里就结束了直到处理事件
总结一下，
1.由底层触发传递给MainThread,由MainThread交给ViewRootImpl的InputStage处理分发输入事件
2.—>View.dispatchPointerEvent
3.—>PhoneWindow.DecorView.dispatchTouchEvent()
4.—>Activity.dispatchTouchEvent()
5.—>PhoneWindow.superDispatchTouchEvent()
6.—>PhoneWindow.DecorView.superDispatchTouchEvent()
7.—>ViewGroup.dispatchTouchEvent()
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