// 点击事件产生后，会直接调用dispatchTouchEvent（）方法
public boolean dispatchTouchEvent(MotionEvent ev) {//代表是否消耗事件boolean consume = false;if (onInterceptTouchEvent(ev)) {//如果onInterceptTouchEvent()返回true则代表当前View拦截了点击事件//则该点击事件则会交给当前View进行处理//即调用onTouchEvent (）方法去处理点击事件consume = onTouchEvent (ev) ;} else {//如果onInterceptTouchEvent()返回false则代表当前View不拦截点击事件//则该点击事件则会继续传递给它的子元素//子元素的dispatchTouchEvent（）就会被调用，重复上述过程//直到点击事件被最终处理为止consume = child.dispatchTouchEvent (ev) ;}return consume;}

public boolean dispatchTouchEvent(MotionEvent ev) {//关注点1//一般事件列开始都是DOWN，所以这里基本是true if (ev.getAction() == MotionEvent.ACTION_DOWN) { //关注点2 onUserInteraction(); } //关注点3 if (getWindow().superDispatchTouchEvent(ev)) { return true; } return onTouchEvent(ev); }

  /**
     * Called whenever a key, touch, or trackball event is dispatched to the
     * activity.  Implement this method if you wish to know that the user has
     * interacted with the device in some way while your activity is running.
     * This callback and {@link #onUserLeaveHint} are intended to help  * activities manage status bar notifications intelligently; specifically,  * for helping activities determine the proper time to cancel a notfication.  *  * <p>All calls to your activity's {@link #onUserLeaveHint} callback will  * be accompanied by calls to {@link #onUserInteraction}. This  * ensures that your activity will be told of relevant user activity such  * as pulling down the notification pane and touching an item there.  *  * <p>Note that this callback will be invoked for the touch down action  * that begins a touch gesture, but may not be invoked for the touch-moved  * and touch-up actions that follow.  *  * @see #onUserLeaveHint()  */ public void onUserInteraction() { }

public boolean superDispatchTouchEvent(MotionEvent event) {return super.dispatchTouchEvent(event); //DecorView继承自FrameLayout //那么它的父类就是ViewGroup 而super.dispatchTouchEvent(event)方法，其实就应该是ViewGroup的dispatchTouchEvent() }

// 发生ACTION_DOWN事件或者已经发生过ACTION_DOWN,并且将mFirstTouchTarget赋值，才进入此区域，主要功能是拦截器final boolean intercepted;if (actionMasked == MotionEvent.ACTION_DOWN|| mFirstTouchTarget != null) {//disallowIntercept：是否禁用事件拦截的功能(默认是false),即不禁用//可以在子View通过调用requestDisallowInterceptTouchEvent方法对这个值进行修改，不让该View拦截事件final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;//默认情况下会进入该方法if (!disallowIntercept) {//调用拦截方法intercepted = onInterceptTouchEvent(ev); ev.setAction(action);} else {intercepted = false;}} else {// 当没有触摸targets，且不是down事件时，开始持续拦截触摸。intercepted = true;}

这一段的内容主要是为判断是否拦截。如果当前事件的MotionEvent.ACTION_DOWN，则进入判断，调用ViewGroup onInterceptTouchEvent()方法的值，判断是否拦截。如果mFirstTouchTarget != null，即已经发生过MotionEvent.ACTION_DOWN，并且该事件已经有ViewGroup的子View进行处理了，那么也进入判断，调用ViewGroup onInterceptTouchEvent()方法的值，判断是否拦截。如果不是以上两种情况，即已经是MOVE或UP事件了，并且之前的事件没有对象进行处理，则设置成true，开始拦截接下来的所有事件。这也就解释了如果子View的onTouchEvent()方法返回false，那么接下来的一些列事件都不会交给他处理。如果VieGroup的onInterceptTouchEvent()第一次执行为true，则mFirstTouchTarget = null，则也会使得接下来不会调用onInterceptTouchEvent()，直接将拦截设置为true。当ViewGroup不拦截事件的时候，事件会向下分发交由它的子View或ViewGroup进行处理。

 /* 从最底层的父视图开始遍历，** 找寻newTouchTarget，即上面的mFirstTouchTarget** 如果已经存在找寻newTouchTarget，说明正在接收触摸事件，则跳出循环。*/
for (int i = childrenCount - 1; i >= 0; i--) {final int childIndex = customOrder? getChildDrawingOrder(childrenCount, i) : i;final View child = (preorderedList == null)? children[childIndex] : preorderedList.get(childIndex);// 如果当前视图无法获取用户焦点，则跳过本次循环if (childWithAccessibilityFocus != null) {if (childWithAccessibilityFocus != child) {continue;}childWithAccessibilityFocus = null;i = childrenCount - 1;}//如果view不可见，或者触摸的坐标点不在view的范围内，则跳过本次循环if (!canViewReceivePointerEvents(child) || !isTransformedTouchPointInView(x, y, child, null)) {ev.setTargetAccessibilityFocus(false);continue;}newTouchTarget = getTouchTarget(child);// 已经开始接收触摸事件,并退出整个循环。if (newTouchTarget != null) {newTouchTarget.pointerIdBits |= idBitsToAssign;break;}//重置取消或抬起标志位//如果触摸位置在child的区域内，则把事件分发给子View或ViewGroupif (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {// 获取TouchDown的时间点mLastTouchDownTime = ev.getDownTime();// 获取TouchDown的Indexif (preorderedList != null) {for (int j = 0; j < childrenCount; j++) {if (children[childIndex] == mChildren[j]) {mLastTouchDownIndex = j;break;}}} else {mLastTouchDownIndex = childIndex;}//获取TouchDown的x,y坐标mLastTouchDownX = ev.getX();mLastTouchDownY = ev.getY();//添加TouchTarget,则mFirstTouchTarget != null。newTouchTarget = addTouchTarget(child, idBitsToAssign);//表示以及分发给NewTouchTargetalreadyDispatchedToNewTouchTarget = true;break;
}

dispatchTransformedTouchEvent()方法实际就是调用子元素的dispatchTouchEvent()方法。 其中dispatchTransformedTouchEvent()方法的重要逻辑如下：if (child == null) {handled = super.dispatchTouchEvent(event);} else {handled = child.dispatchTouchEvent(event);}
由于其中传递的child不为空，所以就会调用子元素的dispatchTouchEvent()。 如果子元素的dispatchTouchEvent()方法返回true，那么mFirstTouchTarget就会被赋值，同时跳出for循环。//添加TouchTarget,则mFirstTouchTarget != null。
newTouchTarget = addTouchTarget(child, idBitsToAssign);//表示以及分发给NewTouchTargetalreadyDispatchedToNewTouchTarget = true;
其中在addTouchTarget(child, idBitsToAssign);内部完成mFirstTouchTarget被赋值。 如果mFirstTouchTarget为空，将会让ViewGroup默认拦截所有操作。 如果遍历所有子View或ViewGroup，都没有消费事件。ViewGroup会自己处理事件。

public boolean dispatchTouchEvent(MotionEvent event) {  if (mOnTouchListener != null && (mViewFlags & ENABLED_MASK) == ENABLED &&  mOnTouchListener.onTouch(this, event)) {  return true;  }  return onTouchEvent(event);
}

//mOnTouchListener是在View类下setOnTouchListener方法里赋值的
public void setOnTouchListener(OnTouchListener l) { //即只要我们给控件注册了Touch事件，mOnTouchListener就一定被赋值（不为空） mOnTouchListener = l; }

public boolean onTouchEvent(MotionEvent event) {  final int viewFlags = mViewFlags;  if ((viewFlags & ENABLED_MASK) == DISABLED) {  // A disabled view that is clickable still consumes the touch  // events, it just doesn't respond to them.  return (((viewFlags & CLICKABLE) == CLICKABLE ||  (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE));  }  if (mTouchDelegate != null) {  if (mTouchDelegate.onTouchEvent(event)) {  return true;  }  }  //如果该控件是可以点击的就会进入到下两行的switch判断中去；if (((viewFlags & CLICKABLE) == CLICKABLE ||  (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)) {  //如果当前的事件是抬起手指，则会进入到MotionEvent.ACTION_UP这个case当中。switch (event.getAction()) {  case MotionEvent.ACTION_UP:  boolean prepressed = (mPrivateFlags & PREPRESSED) != 0;  // 在经过种种判断之后，会执行到关注点1的performClick()方法。//请往下看关注点1if ((mPrivateFlags & PRESSED) != 0 || prepressed) {  // take focus if we don't have it already and we should in  // touch mode.  boolean focusTaken = false;  if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {  focusTaken = requestFocus();  }  if (!mHasPerformedLongPress) {  // This is a tap, so remove the longpress check  removeLongPressCallback();  // Only perform take click actions if we were in the pressed state  if (!focusTaken) {  // Use a Runnable and post this rather than calling  // performClick directly. This lets other visual state  // of the view update before click actions start.  if (mPerformClick == null) {  mPerformClick = new PerformClick();  }  if (!post(mPerformClick)) {  //关注点1//请往下看performClick()的源码分析performClick();  }  }  }  if (mUnsetPressedState == null) {  mUnsetPressedState = new UnsetPressedState();  }  if (prepressed) {  mPrivateFlags |= PRESSED;  refreshDrawableState();  postDelayed(mUnsetPressedState,  ViewConfiguration.getPressedStateDuration());  } else if (!post(mUnsetPressedState)) {  // If the post failed, unpress right now  mUnsetPressedState.run();  }  removeTapCallback();  }  break;  case MotionEvent.ACTION_DOWN:  if (mPendingCheckForTap == null) {  mPendingCheckForTap = new CheckForTap();  }  mPrivateFlags |= PREPRESSED;  mHasPerformedLongPress = false;  postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout());  break;  case MotionEvent.ACTION_CANCEL:  mPrivateFlags &= ~PRESSED;  refreshDrawableState();  removeTapCallback();  break;  case MotionEvent.ACTION_MOVE:  final int x = (int) event.getX();  final int y = (int) event.getY();  // Be lenient about moving outside of buttons  int slop = mTouchSlop;  if ((x < 0 - slop) || (x >= getWidth() + slop) ||  (y < 0 - slop) || (y >= getHeight() + slop)) {  // Outside button  removeTapCallback();  if ((mPrivateFlags & PRESSED) != 0) {  // Remove any future long press/tap checks  removeLongPressCallback();  // Need to switch from pressed to not pressed  mPrivateFlags &= ~PRESSED;  refreshDrawableState();  }  }  break;  }
//如果该控件是可以点击的，就一定会返回truereturn true;  }
//如果该控件是不可以点击的，就一定会返回falsereturn false;
}

public boolean performClick() {  sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);  if (mOnClickListener != null) {  playSoundEffect(SoundEffectConstants.CLICK);  mOnClickListener.onClick(this);  return true;  }  return false;
}

public void setOnClickListener(OnClickListener l) {  if (!isClickable()) {  setClickable(true);  }  mOnClickListener = l;
}

//设置OnTouchListener()button.setOnTouchListener(new View.OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { System.out.println("执行了onTouch(), 动作是:" + event.getAction()); return true; } }); //设置OnClickListener button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { System.out.println("执行了onClick()"); } });

//设置OnTouchListener()button.setOnTouchListener(new View.OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { System.out.println("执行了onTouch(), 动作是:" + event.getAction()); return false; } }); //设置OnClickListener button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { System.out.println("执行了onClick()"); } });