View.onTouchEvent

public boolean onTouchEvent(MotionEvent event) {
    //获取基本信息(没考虑多点，仅考虑单点)	坐标&action  
    final float x = event.getX();
    final float y = event.getY();
    final int viewFlags = mViewFlags;
    final int action = event.getAction();

    //判断是否可点击，长按和上下文点击（上下文菜单，鼠标右键）
    final boolean clickable = ((viewFlags & CLICKABLE) == CLICKABLE
            || (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)
            || (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE;

    //如果是不可用的，直接把事件消费掉，不再向下传递
    if ((viewFlags & ENABLED_MASK) == DISABLED) {
        if (action == MotionEvent.ACTION_UP && (mPrivateFlags & PFLAG_PRESSED) != 0) {
            setPressed(false);
        }
        mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
        // A disabled view that is clickable still consumes the touch
        // events, it just doesn't respond to them.
        return clickable;
    }
    //是否有TouchDelegate，有就消费  -TouchDelegate：点击代理
    if (mTouchDelegate != null) {
        if (mTouchDelegate.onTouchEvent(event)) {
            return true;
        }
    }
   
   //TOOLTIP：解释文本
    if (clickable || (viewFlags & TOOLTIP) == TOOLTIP) {
        switch (action) {
            case MotionEvent.ACTION_UP:
                //手触摸到屏幕标记置空
                mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
                //抬手后 tooltip延迟一会消失
                if ((viewFlags & TOOLTIP) == TOOLTIP) {
                    handleTooltipUp();
                }
                //不可点 各种清空还原
                if (!clickable) {
                    removeTapCallback();
                    removeLongPressCallback();
                    mInContextButtonPress = false;
                    mHasPerformedLongPress = false;
                    mIgnoreNextUpEvent = false;
                    break;
                }
                //是否是点下 &预按下
                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;
		   //如果可以获取焦点  可在实体按键中获取焦点 && 当前没有焦点	
                    if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {
                        focusTaken = requestFocus(); //请求焦点
                    }
                   //如果是预按下 up时设置按下
                    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);
                    }
                   //回调点击
                    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)) {
                                performClickInternal();
                            }
                        }
                    }

                    if (mUnsetPressedState == null) {
                        mUnsetPressedState = new UnsetPressedState();
                    }
 		   //如果是预按下 抬起 效果等4帧
                    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:
		//判断是否触摸到屏幕：存在实体按键->标记为手指按下
                if (event.getSource() == InputDevice.SOURCE_TOUCHSCREEN) {
                    mPrivateFlags3 |= PFLAG3_FINGER_DOWN;
                }
                mHasPerformedLongPress = false;
		//不可点的话，设置长按等待器：为了TOOLTIP，显示提示文字
                if (!clickable) {
                    checkForLongClick(0, x, y); //
                    break;
                }
                //是否是鼠标右键点击，是就显示上下文菜单
                if (performButtonActionOnTouchDown(event)) {
                    break;
                }
		//是否存在在滑动控件中  如果在滑动控件中就 存在触摸延迟
                // 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) { //在滑动控件中
                    mPrivateFlags |= PFLAG_PREPRESSED; //设置预按下状态 在滑动控件中，第一时间判断不了是按下还是滑动
                    if (mPendingCheckForTap == null) {
                        mPendingCheckForTap = new CheckForTap(); //CheckForTap run:还原预按下状态，设置为按下状态，设置一个长按等待器
                    }
                    mPendingCheckForTap.x = event.getX();
                    mPendingCheckForTap.y = event.getY();
                    postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout());
                } else { //不在滑动控件中 置为按下状态，设置一个长按等待器
                    // Not inside a scrolling container, so show the feedback right away
                    setPressed(true, x, y);
                    checkForLongClick(0, x, y);  //0减去已等待
                }
                break;

            case MotionEvent.ACTION_CANCEL: //纯粹各种清空还原
                if (clickable) {
                    setPressed(false);
                }
                removeTapCallback();
                removeLongPressCallback();
                mInContextButtonPress = false;
                mHasPerformedLongPress = false;
                mIgnoreNextUpEvent = false;
                mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
                break;

            case MotionEvent.ACTION_MOVE:
                if (clickable) {
		  //热点改变：如水波纹中心	
                    drawableHotspotChanged(x, y);
                }

                // Be lenient about moving outside of buttons
                //手指移出了控件区域
                if (!pointInView(x, y, mTouchSlop)) { //mTouchSlop：溢出宽容距离
                    // Outside button
                    // Remove any future long press/tap checks
                    //监听移除和flag清除
                    removeTapCallback();
                    removeLongPressCallback();
                    if ((mPrivateFlags & PFLAG_PRESSED) != 0) {
                        setPressed(false);
                    }
                    mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
                }
                break;
        }

        return true;
    }

    return false;
}

 

本文地址：https://blog.csdn.net/rui_yi/article/details/107212489