Explication détaillée du processus de distribution d'événements Android Touch

<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;
 }