【转】Android事件分发机制完全解析，带你从源码的角度彻底理解(下)

1 public class MyLayout extends LinearLayout {
2 
3     public MyLayout(Context context, AttributeSet attrs) {
4         super(context, attrs);
5     }
6 
7 }

 1 <com.example.viewgrouptouchevent.MyLayout xmlns:android="http://schemas.android.com/apk/res/android"
 2     xmlns:tools="http://schemas.android.com/tools"
 3     android:id="@+id/my_layout"
 4     android:layout_width="match_parent"
 5     android:layout_height="match_parent"
 6     android:orientation="vertical" >
 7 
 8     <Button
 9         android:id="@+id/button1"
10         android:layout_width="match_parent"
11         android:layout_height="wrap_content"
12         android:text="Button1" />
13 
14     <Button
15         android:id="@+id/button2"
16         android:layout_width="match_parent"
17         android:layout_height="wrap_content"
18         android:text="Button2" />
19 
20 </com.example.viewgrouptouchevent.MyLayout>

 1 myLayout.setOnTouchListener(new OnTouchListener() {
 2     @Override
 3     public boolean onTouch(View v, MotionEvent event) {
 4         Log.d("TAG", "myLayout on touch");
 5         return false;
 6     }
 7 });
 8 button1.setOnClickListener(new OnClickListener() {
 9     @Override
10     public void onClick(View v) {
11         Log.d("TAG", "You clicked button1");
12     }
13 });
14 button2.setOnClickListener(new OnClickListener() {
15     @Override
16     public void onClick(View v) {
17         Log.d("TAG", "You clicked button2");
18     }
19 });

 1 /**
 2  * Implement this method to intercept all touch screen motion events.  This
 3  * allows you to watch events as they are dispatched to your children, and
 4  * take ownership of the current gesture at any point.
 5  *
 6  * <p>Using this function takes some care, as it has a fairly complicated
 7  * interaction with {@link View#onTouchEvent(MotionEvent)
 8  * View.onTouchEvent(MotionEvent)}, and using it requires implementing
 9  * that method as well as this one in the correct way.  Events will be
10  * received in the following order:
11  *
12  * <ol>
13  * <li> You will receive the down event here.
14  * <li> The down event will be handled either by a child of this view
15  * group, or given to your own onTouchEvent() method to handle; this means
16  * you should implement onTouchEvent() to return true, so you will
17  * continue to see the rest of the gesture (instead of looking for
18  * a parent view to handle it).  Also, by returning true from
19  * onTouchEvent(), you will not receive any following
20  * events in onInterceptTouchEvent() and all touch processing must
21  * happen in onTouchEvent() like normal.
22  * <li> For as long as you return false from this function, each following
23  * event (up to and including the final up) will be delivered first here
24  * and then to the target‘s onTouchEvent().
25  * <li> If you return true from here, you will not receive any
26  * following events: the target view will receive the same event but
27  * with the action {@link MotionEvent#ACTION_CANCEL}, and all further
28  * events will be delivered to your onTouchEvent() method and no longer
29  * appear here.
30  * </ol>
31  *
32  * @param ev The motion event being dispatched down the hierarchy.
33  * @return Return true to steal motion events from the children and have
34  * them dispatched to this ViewGroup through onTouchEvent().
35  * The current target will receive an ACTION_CANCEL event, and no further
36  * messages will be delivered here.
37  */
38 public boolean onInterceptTouchEvent(MotionEvent ev) {
39     return false;
40 }

 1 public class MyLayout extends LinearLayout {
 2 
 3     public MyLayout(Context context, AttributeSet attrs) {
 4         super(context, attrs);
 5     }
 6     
 7     @Override
 8     public boolean onInterceptTouchEvent(MotionEvent ev) {
 9         return true;
10     }
11     
12 }

 1 public boolean dispatchTouchEvent(MotionEvent ev) {
 2     final int action = ev.getAction();
 3     final float xf = ev.getX();
 4     final float yf = ev.getY();
 5     final float scrolledXFloat = xf + mScrollX;
 6     final float scrolledYFloat = yf + mScrollY;
 7     final Rect frame = mTempRect;
 8     boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
 9     if (action == MotionEvent.ACTION_DOWN) {
10         if (mMotionTarget != null) {
11             mMotionTarget = null;
12         }
13         if (disallowIntercept || !onInterceptTouchEvent(ev)) {
14             ev.setAction(MotionEvent.ACTION_DOWN);
15             final int scrolledXInt = (int) scrolledXFloat;
16             final int scrolledYInt = (int) scrolledYFloat;
17             final View[] children = mChildren;
18             final int count = mChildrenCount;
19             for (int i = count - 1; i >= 0; i--) {
20                 final View child = children[i];
21                 if ((child.mViewFlags & VISIBILITY_MASK) == VISIBLE
22                         || child.getAnimation() != null) {
23                     child.getHitRect(frame);
24                     if (frame.contains(scrolledXInt, scrolledYInt)) {
25                         final float xc = scrolledXFloat - child.mLeft;
26                         final float yc = scrolledYFloat - child.mTop;
27                         ev.setLocation(xc, yc);
28                         child.mPrivateFlags &= ~CANCEL_NEXT_UP_EVENT;
29                         if (child.dispatchTouchEvent(ev))  {
30                             mMotionTarget = child;
31                             return true;
32                         }
33                     }
34                 }
35             }
36         }
37     }
38     boolean isUpOrCancel = (action == MotionEvent.ACTION_UP) ||
39             (action == MotionEvent.ACTION_CANCEL);
40     if (isUpOrCancel) {
41         mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT;
42     }
43     final View target = mMotionTarget;
44     if (target == null) {
45         ev.setLocation(xf, yf);
46         if ((mPrivateFlags & CANCEL_NEXT_UP_EVENT) != 0) {
47             ev.setAction(MotionEvent.ACTION_CANCEL);
48             mPrivateFlags &= ~CANCEL_NEXT_UP_EVENT;
49         }
50         return super.dispatchTouchEvent(ev);
51     }
52     if (!disallowIntercept && onInterceptTouchEvent(ev)) {
53         final float xc = scrolledXFloat - (float) target.mLeft;
54         final float yc = scrolledYFloat - (float) target.mTop;
55         mPrivateFlags &= ~CANCEL_NEXT_UP_EVENT;
56         ev.setAction(MotionEvent.ACTION_CANCEL);
57         ev.setLocation(xc, yc);
58         if (!target.dispatchTouchEvent(ev)) {
59         }
60         mMotionTarget = null;
61         return true;
62     }
63     if (isUpOrCancel) {
64         mMotionTarget = null;
65     }
66     final float xc = scrolledXFloat - (float) target.mLeft;
67     final float yc = scrolledYFloat - (float) target.mTop;
68     ev.setLocation(xc, yc);
69     if ((target.mPrivateFlags & CANCEL_NEXT_UP_EVENT) != 0) {
70         ev.setAction(MotionEvent.ACTION_CANCEL);
71         target.mPrivateFlags &= ~CANCEL_NEXT_UP_EVENT;
72         mMotionTarget = null;
73     }
74     return target.dispatchTouchEvent(ev);
75 }