上篇文章从整体上介绍了事件处理的流程Android IMS原理解析之processEvent，本篇文章将详细介绍事件的处理过程；
Event处理
前面分析到，InputDispatcher将触摸事件通过InputChannel发送到目标窗口的接收方WindowInputEventReceiver的dispatchInputEvent()，接下来经过一系列调用会最终调用到ViewPostImeInputStage的processKeyEvent()处理keyEvent、调用processPointerEvent()处理MotionEvent；接下来就一起来看一下对应事件的处理逻辑：
1.processKeyEvent()
此方法主要处理key事件比如：BACK、MENU、HOME等事件：
private int processKeyEvent(QueuedInputEvent q) {
final KeyEvent event = (KeyEvent)q.mEvent;
......
// Deliver the key to the view hierarchy.
if (mView.dispatchKeyEvent(event)) {
return FINISH_HANDLED;
}
.......
}
本文主要分析mView.dispatchKeyEvent(event)，针对activity及back键来进行分析，mView对应Activity的DecorView，看一下DecorView内部的dispatchKeyEvent()方法：
@Override
public boolean dispatchKeyEvent(KeyEvent event) {
final int keyCode = event.getKeyCode();
final int action = event.getAction();
final boolean isDown = action == KeyEvent.ACTION_DOWN;
........
if (!mWindow.isDestroyed()) {
final Window.Callback cb = mWindow.getCallback();
final boolean handled = cb != null && mFeatureId < 0 ? cb.dispatchKeyEvent(event)
: super.dispatchKeyEvent(event);
if (handled) {
return true;
}
}
return isDown ? mWindow.onKeyDown(mFeatureId, event.getKeyCode(), event)
: mWindow.onKeyUp(mFeatureId, event.getKeyCode(), event);
}
mWindow对应着Activity的PhoneWindow，mWindow.getCallback()会返回Activity本身，该处是在Activity的attach()内部执行以下逻辑来执行赋值的，
//Activity.java
final void attach(xxxx) {
......
mWindow = new PhoneWindow(this, window, activityConfigCallback);
mWindow.setCallback(this);
......
}
接着上面的分析，callback不为null，featureId为-1(所有Activity的featureId都是默认为-1)，所以会执行cb.dispatchKeyEvent()即Activity的dispatchKeyEvent()：
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);
}
执行event.dispatch()，对应到KeyEvent里面的dispatch()方法：
public final boolean dispatch(Callback receiver, DispatcherState state,
Object target) {
switch (mAction) {
case ACTION_DOWN: {
mFlags &= ~FLAG_START_TRACKING;
boolean res = receiver.onKeyDown(mKeyCode, this);
.....
return res;
case ACTION_UP:
return receiver.onKeyUp(mKeyCode, this);
.......
}
return false;
}
receiver是Activity，所以会执行Activity内部的onKeyDown()及onKeyUp()方法：
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
.....
onBackPressed();
}
return true;
}
.....
......
}
public boolean onKeyUp(int keyCode, KeyEvent event) {
if (getApplicationInfo().targetSdkVersion
>= Build.VERSION_CODES.ECLAIR) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.isTracking()
&& !event.isCanceled()) {
onBackPressed();
return true;
}
}
return false;
}
所以在Activity界面收到Back事件后，会回调Activty的onBackPressed()方法，默认在onBackPressed()内部关闭activity，如果不想关闭可以重写onBackPressed()或onKeyDown()等，都能实现；
以上就是针对在Activity界面执行Back键时processKeyEvent()的整个执行过程。
用一张流程图总结一下：
BackKey处理流程.png
2.processPointerEvent()
private int processPointerEvent(QueuedInputEvent q) {
final MotionEvent event = (MotionEvent)q.mEvent;
handled = mView.dispatchPointerEvent(event);
......
return handled ? FINISH_HANDLED : FORWARD;
}
在processPointerEvent()内部调用的是mView.dispatchPointerEvent(event)，即DecorView的dispatchPointEvent()，该方法是在View.java内部，一起看一下：
public final boolean dispatchPointerEvent(MotionEvent event) {
if (event.isTouchEvent()) {
return dispatchTouchEvent(event);
} else {
return dispatchGenericMotionEvent(event);
}
}
本文只分析MotionEvent的对应的touch事件，在dispatchPointerEvent()内部会执行dispatchTouchEvent()：
//DecoreView.java
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
final Window.Callback cb = mWindow.getCallback();
return cb != null && !mWindow.isDestroyed() && mFeatureId < 0
? cb.dispatchTouchEvent(ev) : super.dispatchTouchEvent(ev);
}
前面分析到，mWindow.getCallback()为activity，mFeatureId为-1，所以最终执行的是cb.dispatchTouchEvent(ev)，即Activity的dispatchTouchEvent(ev)：
//Activity.java
public boolean dispatchTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
onUserInteraction();
}
if (getWindow().superDispatchTouchEvent(ev)) {
return true;
}
return onTouchEvent(ev);
}
可以看到，先执行getWindow().superDispatchTouchEvent(ev)，如果返回false会执行onTouchEvent()，先看一下PhoneWindow的superDispatchTouchEvent(ev)方法：
//PhoneWindow.java
@Override
public boolean superDispatchTouchEvent(MotionEvent event) {
return mDecor.superDispatchTouchEvent(event);
}
在PhoneWindow内部的superDispatchTouchEvent()执行了DecorView的superDispatchTouchEvent()，又回到DecorView：
//DecorView.java
public boolean superDispatchTouchEvent(MotionEvent event) {
return super.dispatchTouchEvent(event);
}
在DecorView内部调用父类的dispatchTouchEvent，即ViewGroup的dispatchTouchEvent()：
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
......
boolean handled = false;
if (onFilterTouchEventForSecurity(ev)) {
final int action = ev.getAction();
final int actionMasked = action & MotionEvent.ACTION_MASK;
.......
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 {
// There are no touch targets and this action is not an initial down
// so this view group continues to intercept touches.
intercepted = true;
}
.......
if (!canceled && !intercepted) {
.......
dispatchTransformedTouchEvent(en, false, child, x)；
}
.....
return handled;
}
该方法逻辑实现比较长，本文就只拿关键的地方来进行分析，主要有两点：
1.通过onInterceptTouchEvent()来判断是否对事件进行拦截，比如：如果ViewGroup想拦截事件，可以重写onInterceptTouchEvent()来返回true，默认返回false；
2.如果ViewGroup没有对事件进行拦截，那么会从ViewGroup的所有child View里面找到匹配的目标view执行dispatchTransformedTouchEvent()来对事件进行处理，在dispatchTransformedTouchEvent()内部会调用child的dispatchTouchEvent()来对Event进行处理；
//View.java
public boolean dispatchTouchEvent(MotionEvent event) {
.......
boolean result = false;
if (onFilterTouchEventForSecurity(event)) {
......
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;
}
该方法内部主要有两项重点：
1.先判断View(控件)是否实现了mOnTouchListener，如果没实现，直接跳过；否则判断onTouch()返回值，如果返回true，则result为true，如果返回false，则result为false；
2.如果满足result为false，则执行onTouchEvent(event)；
public boolean onTouchEvent(MotionEvent event) {
final float x = event.getX();
final float y = event.getY();
final int viewFlags = mViewFlags;
final int action = event.getAction();
final boolean clickable = ((viewFlags & CLICKABLE) == CLICKABLE
|| (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)
|| (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE;
.......
if (clickable || (viewFlags & TOOLTIP) == TOOLTIP) {
switch (action) {
case MotionEvent.ACTION_UP:
......
if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) {
// This is a tap, so remove the longpress check
removeLongPressCallback();
// Only perform take click actions if we were in the pressed state
if (!focusTaken) {
if (mPerformClick == null) {
mPerformClick = new PerformClick();
}
if (!post(mPerformClick)) {
performClick();
}
}
}
......
break;
case MotionEvent.ACTION_DOWN:
mHasPerformedLongPress = false;
.......
checkForLongClick(0, x, y);
break;
.........
}
return true;
}
return false;
}
在onTouchEvent()内部逻辑处理如下，只分析DOWN和UP事件，先看DOWN事件：
因为在DOWN时，可能会出现长按不放的情况，那么就会触发LongClick事件，执行checkForLongClick(0, x, y)来进行判断：
private void checkForLongClick(int delayOffset, float x, float y) {
if ((mViewFlags & LONG_CLICKABLE) == LONG_CLICKABLE || (mViewFlags & TOOLTIP) == TOOLTIP) {
mHasPerformedLongPress = false;
if (mPendingCheckForLongPress == null) {
mPendingCheckForLongPress = new CheckForLongPress();
}
mPendingCheckForLongPress.setAnchor(x, y);
mPendingCheckForLongPress.rememberWindowAttachCount();
mPendingCheckForLongPress.rememberPressedState();
postDelayed(mPendingCheckForLongPress,
ViewConfiguration.getLongPressTimeout() - delayOffset);
}
}
private final class CheckForLongPress implements Runnable {
@Override
public void run() {
if ((mOriginalPressedState == isPressed()) && (mParent != null)
&& mOriginalWindowAttachCount == mWindowAttachCount) {
if (performLongClick(mX, mY)) {
mHasPerformedLongPress = true;
}
}
}
......
}
public boolean performLongClick(float x, float y) {
mLongClickX = x;
mLongClickY = y;
final boolean handled = performLongClick();
mLongClickX = Float.NaN;
mLongClickY = Float.NaN;
return handled;
}
public boolean performLongClick() {
return performLongClickInternal(mLongClickX, mLongClickY);
}
private boolean performLongClickInternal(float x, float y) {
sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_LONG_CLICKED);
boolean handled = false;
final ListenerInfo li = mListenerInfo;
if (li != null && li.mOnLongClickListener != null) {
handled = li.mOnLongClickListener.onLongClick(View.this);
}
......
if (handled) {
performHapticFeedback(HapticFeedbackConstants.LONG_PRESS);
}
return handled;
}
通过以上调用流程可以看到，最终返回的值由是OnLongClickListener的onLongClick()来决定，如果返回true的话，那么在CheckForLongPress里面会设置mHasPerformedLongPress为true，如果返回false的话，那么mHasPerformedLongPress还是false；
接下来分析Up事件，我们知道onClick()就是在Up后进行处理的，一起看一下UP事件处理：
case MotionEvent.ACTION_UP:
if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) {
// This is a tap, so remove the longpress check
removeLongPressCallback();
// Only perform take click actions if we were in the pressed state
if (!focusTaken) {
if (mPerformClick == null) {
mPerformClick = new PerformClick();
}
if (!post(mPerformClick)) {
performClick();
}
}
}
如果先处理的onLongClick()且返回true，那么mHasPerformedLongPress值为true，那么就不会处理后续事件了，如果返回false，那么mHasPerformedLongPress为false，那么就会执行post(mPerformClick)，一起看一下执行逻辑：
private final class PerformClick implements Runnable {
@Override
public void run() {
performClick();
}
}
public boolean performClick() {
final boolean result;
final ListenerInfo li = mListenerInfo;
if (li != null && li.mOnClickListener != null) {
playSoundEffect(SoundEffectConstants.CLICK);
li.mOnClickListener.onClick(this);
result = true;
} else {
result = false;
}
return result;
}
通过上面可以看到，在performClick()里面会执行OnClickListener的onClick()方法，onClick事件也就分析完了；
用一张流程图总结一下：
MotionEvent处理流程.png
简单总结：
1.在Motion事件传递时，传递顺序为：DecorView-->Activity-->PhoneWindow-->DecorView-->ViewGroup-->Child View；
2.在ViewGroup可以对事件进行拦截，如果不拦截的话，会遍历所有子view来找到目标view执行dispatchTouchEvent()响应事件；
3.在dispatchTouchEvent()内部执行顺序为：OnTouchListenter.onTouch()-->onTouchEvent()；
4.在onTouchEvent()内部处理DOWN和UP事件，DOWN事件里面会最终执行onLongClick()回调，UP事件里面会最终执行onClick()回调，如果onLongClick()返回true，那么onClick()就不会回调了，反之回调；
至此，IMS从事件接收到发送到处理就完成了。
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