Android View的Touch事件分发

/**
    * 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)) {
           if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {
               result = true;
           }
           //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;
   }

static class ListenerInfo {
        /**
         * Listener used to dispatch focus change events.
         * This field should be made private, so it is hidden from the SDK.
         * {@hide}
         */
        protected OnFocusChangeListener mOnFocusChangeListener;
        /**
         * Listeners for layout change events.
         */
        private ArrayList<OnLayoutChangeListener> mOnLayoutChangeListeners;
        protected OnScrollChangeListener mOnScrollChangeListener;
        /**
         * Listeners for attach events.
         */
        private CopyOnWriteArrayList<OnAttachStateChangeListener> mOnAttachStateChangeListeners;
        /**
         * Listener used to dispatch click events.
         * This field should be made private, so it is hidden from the SDK.
         * {@hide}
         */
        public OnClickListener mOnClickListener;
        /**
         * Listener used to dispatch long click events.
         * This field should be made private, so it is hidden from the SDK.
         * {@hide}
         */
        protected OnLongClickListener mOnLongClickListener;
        /**
         * Listener used to dispatch context click events. This field should be made private, so it
         * is hidden from the SDK.
         * {@hide}
         */
        protected OnContextClickListener mOnContextClickListener;
        /**
         * Listener used to build the context menu.
         * This field should be made private, so it is hidden from the SDK.
         * {@hide}
         */
        protected OnCreateContextMenuListener mOnCreateContextMenuListener;
        private OnKeyListener mOnKeyListener;
        private OnTouchListener mOnTouchListener;
        private OnHoverListener mOnHoverListener;
        private OnGenericMotionListener mOnGenericMotionListener;
        private OnDragListener mOnDragListener;
        private OnSystemUiVisibilityChangeListener mOnSystemUiVisibilityChangeListener;
        OnApplyWindowInsetsListener mOnApplyWindowInsetsListener;
    }

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;
}

public boolean onTouchEvent(MotionEvent event) {
          //......代码太长  省略
           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, x, y);
                   }
                   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;
   }

/**
    * Call this view's OnClickListener, if it is defined.  Performs all normal
    * actions associated with clicking: reporting accessibility event, playing
    * a sound, etc.
    *
    * @return True there was an assigned OnClickListener that was called, false
    *         otherwise is returned.
    */
   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;
   }

      case MotionEvent.ACTION_DOWN:
         //...
         checkForLongClick(0, x, y);
         break;

//检测长按事件
private void checkForLongClick(int delayOffset, float x, float y) {
        if ((mViewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) {
            mHasPerformedLongPress = false;

            if (mPendingCheckForLongPress == null) {
                mPendingCheckForLongPress = new CheckForLongPress();
            }
            mPendingCheckForLongPress.setAnchor(x, y);
            mPendingCheckForLongPress.rememberWindowAttachCount();
            postDelayed(mPendingCheckForLongPress,
                    ViewConfiguration.getLongPressTimeout() - delayOffset);
        }
    }

 private final class CheckForLongPress implements Runnable {
        private int mOriginalWindowAttachCount;
        private float mX;
        private float mY;

        @Override
        public void run() {
            if (isPressed() && (mParent != null)
                    && mOriginalWindowAttachCount == mWindowAttachCount) {
              //触发长按事件
                if (performLongClick(mX, mY)) {
                    mHasPerformedLongPress = true;
                }
            }
        }

        public void setAnchor(float x, float y) {
            mX = x;
            mY = y;
        }

        public void rememberWindowAttachCount() {
            mOriginalWindowAttachCount = mWindowAttachCount;
        }
    }



public boolean performLongClick(float x, float y) {
        mLongClickX = x;
        mLongClickY = y;
        final boolean handled = performLongClick();
        mLongClickX = Float.NaN;
        mLongClickY = Float.NaN;
        return handled;
    }

public boolean performLongClick() {
        return performLongClickInternal(mLongClickX, mLongClickY);
    }

 private boolean performLongClickInternal(float x, float y) {
        sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_LONG_CLICKED);

        boolean handled = false;
        final ListenerInfo li = mListenerInfo;
        if (li != null && li.mOnLongClickListener != null) {
            handled = li.mOnLongClickListener.onLongClick(View.this);
        }
        if (!handled) {
            final boolean isAnchored = !Float.isNaN(x) && !Float.isNaN(y);
            handled = isAnchored ? showContextMenu(x, y) : showContextMenu();
        }
        if (handled) {
            performHapticFeedback(HapticFeedbackConstants.LONG_PRESS);
        }
        return handled;
    }