Android事件的分发机制详解

btn.setOnClickListener(new View.OnClickListener() {      @Override      public void onClick(View v) {        Log.i("Tag", "This is button onClick event");      }    });    btn.setOnTouchListener(new View.OnTouchListener() {      @Override      public boolean onTouch(View v, MotionEvent event) {        Log.i("Tag", "This is button onTouch action" + event.getAction());        return false;      }    });

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;  }

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;  }

public void setOnClickListener(@Nullable OnClickListener l) {    if (!isClickable()) {      setClickable(true);    }    getListenerInfo().mOnClickListener = l;  }