Android中onTouch事件传递机制 详细分析Android中onTouch事件传递机制

/**
 * 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 the event should be handled by accessibility focus first.
 if (event.isTargetAccessibilityFocus()) {
 // We don't have focus or no virtual descendant has it, do not handle the event.
 if (!isAccessibilityFocusedViewOrHost()) {
  return false;
 }
 // We have focus and got the event, then use normal event dispatch.
 event.setTargetAccessibilityFocus(false);
 }

 boolean result = false;

 if (mInputEventConsistencyVerifier != null) {
 mInputEventConsistencyVerifier.onTouchEvent(event, 0);
 }

 final int actionMasked = event.getActionMasked();
 if (actionMasked == MotionEvent.ACTION_DOWN) {
 // Defensive cleanup for new gesture
 stopNestedScroll();
 }

 if (onFilterTouchEventForSecurity(event)) {
 //noinspection SimplifiableIfStatement
 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;
 }
 }

 if (!result && mInputEventConsistencyVerifier != null) {
 mInputEventConsistencyVerifier.onUnhandledEvent(event, 0);
 }

 // Clean up after nested scrolls if this is the end of a gesture;
 // also cancel it if we tried an ACTION_DOWN but we didn't want the rest
 // of the gesture.
 if (actionMasked == MotionEvent.ACTION_UP ||
  actionMasked == MotionEvent.ACTION_CANCEL ||
  (actionMasked == MotionEvent.ACTION_DOWN && !result)) {
 stopNestedScroll();
 }

 return result;
}

ListenerInfo getListenerInfo() {
 if (mListenerInfo != null) {
 return mListenerInfo;
 }
 mListenerInfo = new ListenerInfo();
 return mListenerInfo;
}

/**
 * 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) {
 getListenerInfo().mOnTouchListener = l;
}

/**
 * Implement this method to handle touch screen motion events.
 * <p>
 * If this method is used to detect click actions, it is recommended that
 * the actions be performed by implementing and calling
 * {@link #performClick()}. This will ensure consistent system behavior,
 * including:
 * <ul>
 * <li>obeying click sound preferences
 * <li>dispatching OnClickListener calls
 * <li>handling {@link AccessibilityNodeInfo#ACTION_CLICK ACTION_CLICK} when
 * accessibility features are enabled
 * </ul>
 *
 * @param event The motion event.
 * @return True if the event was handled, false otherwise.
 */
public boolean onTouchEvent(MotionEvent event) {
 final float x = event.getX();
 final float y = event.getY();
 final int viewFlags = mViewFlags;
 final int action = event.getAction();

 if ((viewFlags & ENABLED_MASK) == DISABLED) {
 if (action == MotionEvent.ACTION_UP && (mPrivateFlags & PFLAG_PRESSED) != 0) {
  setPressed(false);
 }
 // 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)
  || (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE);
 }

 if (mTouchDelegate != null) {
 if (mTouchDelegate.onTouchEvent(event)) {
  return true;
 }
 }

 if (((viewFlags & CLICKABLE) == CLICKABLE ||
  (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) ||
  (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE) {
 switch (action) {
  case MotionEvent.ACTION_UP:
  boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != 0;
  if ((mPrivateFlags & PFLAG_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 (prepressed) {
   // The button is being released before we actually
   // showed it as pressed. Make it show the pressed
   // state now (before scheduling the click) to ensure
   // the user sees it.
   setPressed(true, x, y);
   }

   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) {
    // 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)) {
    performClick();
    }
   }
   }

   if (mUnsetPressedState == null) {
   mUnsetPressedState = new UnsetPressedState();
   }

   if (prepressed) {
   postDelayed(mUnsetPressedState,
    ViewConfiguration.getPressedStateDuration());
   } else if (!post(mUnsetPressedState)) {
   // If the post failed, unpress right now
   mUnsetPressedState.run();
   }

   removeTapCallback();
  }
  mIgnoreNextUpEvent = false;
  break;

  case MotionEvent.ACTION_DOWN:
  mHasPerformedLongPress = false;

  if (performButtonActionOnTouchDown(event)) {
   break;
  }

  // Walk up the hierarchy to determine if we're inside a scrolling container.
  boolean isInScrollingContainer = isInScrollingContainer();

  // For views inside a scrolling container, delay the pressed feedback for
  // a short period in case this is a scroll.
  if (isInScrollingContainer) {
   mPrivateFlags |= PFLAG_PREPRESSED;
   if (mPendingCheckForTap == null) {
   mPendingCheckForTap = new CheckForTap();
   }
   mPendingCheckForTap.x = event.getX();
   mPendingCheckForTap.y = event.getY();
   postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout());
  } else {
   // Not inside a scrolling container, so show the feedback right away
   setPressed(true, x, y);
   checkForLongClick(0);
  }
  break;

  case MotionEvent.ACTION_CANCEL:
  setPressed(false);
  removeTapCallback();
  removeLongPressCallback();
  mInContextButtonPress = false;
  mHasPerformedLongPress = false;
  mIgnoreNextUpEvent = false;
  break;

  case MotionEvent.ACTION_MOVE:
  drawableHotspotChanged(x, y);

  // Be lenient about moving outside of buttons
  if (!pointInView(x, y, mTouchSlop)) {
   // Outside button
   removeTapCallback();
   if ((mPrivateFlags & PFLAG_PRESSED) != 0) {
   // Remove any future long press/tap checks
   removeLongPressCallback();

   setPressed(false);
   }
  }
  break;
 }

 return true;
 }

 return false;
}

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;
 }

 sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);
 return result;
}

/**
 * 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(@Nullable OnClickListener l) {
 if (!isClickable()) {
 setClickable(true);
 }
 getListenerInfo().mOnClickListener = l;
}