Android Touch事件分发过程详解

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" 
  xmlns:tools="http://schemas.android.com/tools" 
  android:id="@+id/container" 
  android:layout_width="match_parent" 
  android:layout_height="match_parent" 
  android:layout_gravity="center" 
  tools:context="com.example.touch_event.MainActivity" 
  tools:ignore="MergeRootFrame" > 
 
  <Button 
    android:id="@+id/my_button" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/hello_world" /> 
 
</FrameLayout> 

public class MainActivity extends Activity { 
 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
 
    Button mBtn = (Button) findViewById(R.id.my_button); 
    mBtn.setOnTouchListener(new OnTouchListener() { 
 
      @Override 
      public boolean onTouch(View v, MotionEvent event) { 
        Log.d("", "### onTouch : " + event.getAction()); 
        return false; 
      } 
    }); 
    mBtn.setOnClickListener(new OnClickListener() { 
 
      @Override 
      public void onClick(View v) { 
        Log.d("", "### onClick : " + v); 
      } 
    }); 
 
  } 
 
  @Override 
  public boolean dispatchTouchEvent(MotionEvent ev) { 
    Log.d("", "### activity dispatchTouchEvent"); 
    return super.dispatchTouchEvent(ev); 
  } 
} 

08-31 03:03:56.116: D/(1560): ### activity dispatchTouchEvent 
08-31 03:03:56.116: D/(1560): ### onTouch : 0 
08-31 03:03:56.196: D/(1560): ### activity dispatchTouchEvent 
08-31 03:03:56.196: D/(1560): ### onTouch : 1 
08-31 03:03:56.196: D/(1560): ### onClick : android.widget.Button{52860d98 VFED..C. ...PH... 0,0-1080,144 #7f05003d app:id/my_button} 

public final class MotionEvent extends InputEvent implements Parcelable { 
// 代码省略 
  public static final int ACTION_DOWN       = 0;  // 按下事件 
  public static final int ACTION_UP        = 1;  // 抬起事件  
  public static final int ACTION_MOVE       = 2;  // 手势移动事件 
  public static final int ACTION_CANCEL      = 3;  // 取消 
 // 代码省略 
} 

08-31 03:04:45.408: D/(1560): ### activity dispatchTouchEvent08-31  
03:04:45.512: D/(1560): ### activity dispatchTouchEvent 

08-31 03:06:04.764: D/(1612): ### activity dispatchTouchEvent 
08-31 03:06:04.764: D/(1612): ### onTouch : 0 
08-31 03:06:04.868: D/(1612): ### activity dispatchTouchEvent 
08-31 03:06:04.868: D/(1612): ### onTouch : 1 

public final class ViewRoot extends Handler implements ViewParent, 
    View.AttachInfo.Callbacks { 
      // 代码省略 
  private final InputHandler mInputHandler = new InputHandler() { 
    public void handleKey(KeyEvent event, Runnable finishedCallback) { 
      startInputEvent(finishedCallback); 
      dispatchKey(event, true); 
    } 
    public void handleMotion(MotionEvent event, Runnable finishedCallback) { 
      startInputEvent(finishedCallback); 
      dispatchMotion(event, true);   // 1、handle 触摸消息 
    } 
  }; 
    // 代码省略 
  // 2、分发触摸消息 
  private void dispatchMotion(MotionEvent event, boolean sendDone) { 
    int source = event.getSource(); 
    if ((source & InputDevice.SOURCE_CLASS_POINTER) != 0) { 
      dispatchPointer(event, sendDone);   // 分发触摸消息 
    } else if ((source & InputDevice.SOURCE_CLASS_TRACKBALL) != 0) { 
      dispatchTrackball(event, sendDone); 
    } else { 
      // TODO 
      Log.v(TAG, "Dropping unsupported motion event (unimplemented): " + event); 
      if (sendDone) { 
        finishInputEvent(); 
      } 
    } 
  } 
  // 3、通过Handler投递消息 
  private void dispatchPointer(MotionEvent event, boolean sendDone) { 
    Message msg = obtainMessage(DISPATCH_POINTER); 
    msg.obj = event; 
    msg.arg1 = sendDone ? 1 : 0; 
    sendMessageAtTime(msg, event.getEventTime()); 
  } 
  @Override 
  public void handleMessage(Message msg) {      // ViewRoot覆写handlerMessage来处理各种消息 
    switch (msg.what) { 
      // 代码省略 
    case DO_TRAVERSAL: 
      if (mProfile) { 
        Debug.startMethodTracing("ViewRoot"); 
      } 
 
      performTraversals(); 
 
      if (mProfile) { 
        Debug.stopMethodTracing(); 
        mProfile = false; 
      } 
      break; 
 
    case DISPATCH_POINTER: {    // 4、处理DISPATCH_POINTER类型的消息，即触摸屏幕的消息 
      MotionEvent event = (MotionEvent) msg.obj; 
      try { 
        deliverPointerEvent(event); // 5、处理触摸消息 
      } finally { 
        event.recycle(); 
        if (msg.arg1 != 0) { 
          finishInputEvent(); 
        } 
        if (LOCAL_LOGV || WATCH_POINTER) Log.i(TAG, "Done dispatching!"); 
      } 
    } break; 
    // 代码省略 
  } 
  // 6、真正的处理事件 
  private void deliverPointerEvent(MotionEvent event) { 
    if (mTranslator != null) { 
      mTranslator.translateEventInScreenToAppWindow(event); 
    } 
    boolean handled; 
    if (mView != null && mAdded) { 
      // enter touch mode on the down 
      boolean isDown = event.getAction() == MotionEvent.ACTION_DOWN; 
      if (isDown) { 
        ensureTouchMode(true);  // 如果是ACTION_DOWN事件则进入触摸模式，否则为按键模式。 
      } 
      if(Config.LOGV) { 
        captureMotionLog("captureDispatchPointer", event); 
      } 
      if (mCurScrollY != 0) { 
        event.offsetLocation(0, mCurScrollY);  // 物理坐标向逻辑坐标的转换 
      } 
      if (MEASURE_LATENCY) { 
        lt.sample("A Dispatching TouchEvents", System.nanoTime() - event.getEventTimeNano()); 
      } 
      // 7、分发事件，如果是窗口类型，则这里的mView对应的就是PhonwWindow中的DecorView，否则为根视图的ViewGroup。 
      handled = mView.dispatchTouchEvent(event); 
      // 代码省略   
    } 
  } 
  // 代码省略 
}  

public boolean dispatchTouchEvent(MotionEvent ev) { 
   if (ev.getAction() == MotionEvent.ACTION_DOWN) { 
     onUserInteraction(); 
   } 
   if (getWindow().superDispatchTouchEvent(ev)) {   // 1、调用的是PhoneWindow的superDispatchTouchEvent(ev) 
 
     return true; 
   } 
   return onTouchEvent(ev); 
 } 
 
 public void onUserInteraction() { 
 } 

Log.d("", "### Activiti中getWindow()获取的类型是 : " + this.getWindow()) ; 

08-31 03:40:17.036: D/(1688): ### Activiti中getWindow()获取的类型是 : com.android.internal.policy.impl.PhoneWindow@5287fe38 

@Override 
public boolean superDispatchTouchEvent(MotionEvent event) { 
  return mDecor.superDispatchTouchEvent(event); 
} 

// This is the top-level view of the window, containing the window decor. 
private DecorView mDecor; 

  private final class DecorView extends FrameLayout implements RootViewSurfaceTaker { 
    /* package */int mDefaultOpacity = PixelFormat.OPAQUE; 
 
    /** The feature ID of the panel, or -1 if this is the application's DecorView */ 
    private final int mFeatureId; 
 
    private final Rect mDrawingBounds = new Rect(); 
 
    private final Rect mBackgroundPadding = new Rect(); 
 
    private final Rect mFramePadding = new Rect(); 
 
    private final Rect mFrameOffsets = new Rect(); 
 
    private boolean mChanging; 
 
    private Drawable mMenuBackground; 
    private boolean mWatchingForMenu; 
    private int mDownY; 
 
    public DecorView(Context context, int featureId) { 
      super(context); 
      mFeatureId = featureId; 
    } 
 
    @Override 
    public boolean dispatchKeyEvent(KeyEvent event) { 
      final int keyCode = event.getKeyCode(); 
      // 代码省略 
      return isDown ? PhoneWindow.this.onKeyDown(mFeatureId, event.getKeyCode(), event) 
          : PhoneWindow.this.onKeyUp(mFeatureId, event.getKeyCode(), event); 
    } 
 
    @Override 
    public boolean dispatchTouchEvent(MotionEvent ev) { 
      final Callback cb = getCallback(); 
      return cb != null && mFeatureId < 0 ? cb.dispatchTouchEvent(ev) : super 
          .dispatchTouchEvent(ev); 
    } 
 
    @Override 
    public boolean dispatchTrackballEvent(MotionEvent ev) { 
      final Callback cb = getCallback(); 
      return cb != null && mFeatureId < 0 ? cb.dispatchTrackballEvent(ev) : super 
          .dispatchTrackballEvent(ev); 
    } 
 
    public boolean superDispatchKeyEvent(KeyEvent event) { 
      return super.dispatchKeyEvent(event); 
    } 
 
    public boolean superDispatchTouchEvent(MotionEvent event) { 
      return super.dispatchTouchEvent(event); 
    } 
 
    public boolean superDispatchTrackballEvent(MotionEvent event) { 
      return super.dispatchTrackballEvent(event); 
    } 
 
    @Override 
    public boolean onTouchEvent(MotionEvent event) { 
      return onInterceptTouchEvent(event); 
    } 
// 代码省略 
} 

/** 
 * {@inheritDoc} 
 */ 
@Override 
public boolean dispatchTouchEvent(MotionEvent ev) { 
  if (!onFilterTouchEventForSecurity(ev)) { 
    return false; 
  } 
 
  final int action = ev.getAction(); 
  final float xf = ev.getX(); 
  final float yf = ev.getY(); 
  final float scrolledXFloat = xf + mScrollX; 
  final float scrolledYFloat = yf + mScrollY; 
  final Rect frame = mTempRect; 
 
  boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0; 
 
  if (action == MotionEvent.ACTION_DOWN) { 
    if (mMotionTarget != null) { 
      // this is weird, we got a pen down, but we thought it was 
      // already down! 
      // XXX: We should probably send an ACTION_UP to the current 
      // target. 
      mMotionTarget = null; 
    } 
    // If we're disallowing intercept or if we're allowing and we didn't 
    // intercept 
    if (disallowIntercept || !onInterceptTouchEvent(ev))     // 1、是否禁用拦截、是否拦截事件 
      // reset this event's action (just to protect ourselves) 
      ev.setAction(MotionEvent.ACTION_DOWN); 
      // We know we want to dispatch the event down, find a child 
      // who can handle it, start with the front-most child. 
      final int scrolledXInt = (int) scrolledXFloat; 
      final int scrolledYInt = (int) scrolledYFloat; 
      final View[] children = mChildren; 
      final int count = mChildrenCount; 
 
      for (int i = count - 1; i >= 0; i--)    // 2、迭代所有子view，查找触摸事件在哪个子view的坐标范围内 
        final View child = children[i]; 
        if ((child.mViewFlags & VISIBILITY_MASK) == VISIBLE 
            || child.getAnimation() != null) { 
          child.getHitRect(frame);        // 3、获取child的坐标范围 
          if (frame.contains(scrolledXInt, scrolledYInt))  // 4、判断发生该事件坐标是否在该child坐标范围内 
            // offset the event to the view's coordinate system 
            final float xc = scrolledXFloat - child.mLeft; 
            final float yc = scrolledYFloat - child.mTop; 
            ev.setLocation(xc, yc); 
            child.mPrivateFlags &= ~CANCEL_NEXT_UP_EVENT; 
            if (child.dispatchTouchEvent(ev))   // 5、child处理该事件 
              // Event handled, we have a target now. 
              mMotionTarget = child; 
              return true; 
            } 
            // The event didn't get handled, try the next view. 
            // Don't reset the event's location, it's not 
            // necessary here. 
          } 
        } 
      } 
    } 
  } 
 
  boolean isUpOrCancel = (action == MotionEvent.ACTION_UP) || 
      (action == MotionEvent.ACTION_CANCEL); 
 
  if (isUpOrCancel) { 
    // Note, we've already copied the previous state to our local 
    // variable, so this takes effect on the next event 
    mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT; 
  } 
 
  // The event wasn't an ACTION_DOWN, dispatch it to our target if 
  // we have one. 
  final View target = mMotionTarget; 
  if (target == null) { 
    // We don't have a target, this means we're handling the 
    // event as a regular view. 
    ev.setLocation(xf, yf); 
    if ((mPrivateFlags & CANCEL_NEXT_UP_EVENT) != 0) { 
      ev.setAction(MotionEvent.ACTION_CANCEL); 
      mPrivateFlags &= ~CANCEL_NEXT_UP_EVENT; 
    } 
    return super.dispatchTouchEvent(ev); 
  } 
 
  // if have a target, see if we're allowed to and want to intercept its 
  // events 
  if (!disallowIntercept && onInterceptTouchEvent(ev)) { 
    final float xc = scrolledXFloat - (float) target.mLeft; 
    final float yc = scrolledYFloat - (float) target.mTop; 
    mPrivateFlags &= ~CANCEL_NEXT_UP_EVENT; 
    ev.setAction(MotionEvent.ACTION_CANCEL); 
    ev.setLocation(xc, yc); 
    if (!target.dispatchTouchEvent(ev)) { 
      // target didn't handle ACTION_CANCEL. not much we can do 
      // but they should have. 
    } 
    // clear the target 
    mMotionTarget = null; 
    // Don't dispatch this event to our own view, because we already 
    // saw it when intercepting; we just want to give the following 
    // event to the normal onTouchEvent(). 
    return true; 
  } 
 
  if (isUpOrCancel) { 
    mMotionTarget = null; 
  } 
 
  // finally offset the event to the target's coordinate system and 
  // dispatch the event. 
  final float xc = scrolledXFloat - (float) target.mLeft; 
  final float yc = scrolledYFloat - (float) target.mTop; 
  ev.setLocation(xc, yc); 
 
  if ((target.mPrivateFlags & CANCEL_NEXT_UP_EVENT) != 0) { 
    ev.setAction(MotionEvent.ACTION_CANCEL); 
    target.mPrivateFlags &= ~CANCEL_NEXT_UP_EVENT; 
    mMotionTarget = null; 
  } 
 
  return target.dispatchTouchEvent(ev); 
} 

/** 
 * Pass the touch screen motion event down to the target view, or this 
 * view if it is the target. 
 * 
 * @param event The motion event to be dispatched. 
 * @return True if the event was handled by the view, false otherwise. 
 */ 
public boolean dispatchTouchEvent(MotionEvent event) { 
  if (!onFilterTouchEventForSecurity(event)) { 
    return false; 
  } 
 
  if (mOnTouchListener != null && (mViewFlags & ENABLED_MASK) == ENABLED && 
      mOnTouchListener.onTouch(this, event)) { 
    return true; 
  } 
  return onTouchEvent(event); 
} 

/** 
 * Register a callback to be invoked when a touch event is sent to this view. 
 * @param l the touch listener to attach to this view 
 */ 
public void setOnTouchListener(OnTouchListener l) { 
  mOnTouchListener = l; 
} 

/** 
 * Implement this method to handle touch screen motion events. 
 * 
 * @param event The motion event. 
 * @return True if the event was handled, false otherwise. 
 */ 
public boolean onTouchEvent(MotionEvent event) { 
  final int viewFlags = mViewFlags; 
 
  if ((viewFlags & ENABLED_MASK) == DISABLED)    // 1、判断该view是否enable 
    // 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; 
    } 
  } 
 
  if (((viewFlags & CLICKABLE) == CLICKABLE || 
      (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)) // 2、是否是clickable或者long clickable 
    switch (event.getAction()) { 
      case MotionEvent.ACTION_UP:          // 抬起事件 
        boolean prepressed = (mPrivateFlags & PREPRESSED) != 0; 
        if ((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();    // 获取焦点 
          } 
 
          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))   // post 
                performClick();     // 3、点击事件处理 
              } 
            } 
          } 
 
          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; 
    } 
    return true; 
  } 
 
  return false; 
} 

/** 
 * Causes the Runnable to be added to the message queue. 
 * The runnable will be run on the user interface thread. 
 * 
 * @param action The Runnable that will be executed. 
 * 
 * @return Returns true if the Runnable was successfully placed in to the 
 *     message queue. Returns false on failure, usually because the 
 *     looper processing the message queue is exiting. 
 */ 
public boolean post(Runnable action) { 
  Handler handler; 
  if (mAttachInfo != null) { 
    handler = mAttachInfo.mHandler; 
  } else { 
    // Assume that post will succeed later 
    ViewRoot.getRunQueue().post(action); 
    return true; 
  } 
 
  return handler.post(action); 
} 

private final class PerformClick implements Runnable { 
  public void run() { 
    performClick(); 
  } 
} 

/** 
 * Register a callback to be invoked when this view is clicked. If this view is not 
 * clickable, it becomes clickable. 
 * 
 * @param l The callback that will run 
 * 
 * @see #setClickable(boolean) 
 */ 
 public void setOnClickListener(OnClickListener l) { 
   if (!isClickable()) { 
     setClickable(true); 
   } 
   mOnClickListener = l; 
 } 
 
 /** 
 * Call this view's OnClickListener, if it is defined. 
 * 
 * @return True there was an assigned OnClickListener that was called, false 
 *     otherwise is returned. 
 */ 
 public boolean performClick() { 
   sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED); 
 
   if (mOnClickListener != null) { 
     playSoundEffect(SoundEffectConstants.CLICK); 
     mOnClickListener.onClick(this); 
     return true; 
   } 
 
   return false; 
 }