public boolean dispatchTouchEvent(MotionEvent event) {
    ...
    boolean result = false;	// result 为返回值，主要作用是告诉调用者事件是否已经被消费。
    if (onFilterTouchEventForSecurity(event)) {
        ListenerInfo li = mListenerInfo;
        /** 
         * 如果设置了OnTouchListener，并且当前 View 可点击，就调用监听器的 onTouch 方法，
         * 如果 onTouch 方法返回值为 true，就设置 result 为 true。
         */
        if (li != null && li.mOnTouchListener != null
                && (mViewFlags & ENABLED_MASK) == ENABLED
                && li.mOnTouchListener.onTouch(this, event)) {
            result = true;
        }
      
        /** 
         * 如果 result 为 false，则调用自身的 onTouchEvent。
         * 如果 onTouchEvent 返回值为 true，则设置 result 为 true。
         */
        if (!result && onTouchEvent(event)) {
            result = true;
        }
    }
    ...
    return result;
}

public boolean onTouchEvent(MotionEvent event) {
    ...
    final int action = event.getAction();
  	// 检查各种 clickable
    if (((viewFlags & CLICKABLE) == CLICKABLE ||
            (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) ||
            (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE) {
        switch (action) {
            case MotionEvent.ACTION_UP:
                ...
                removeLongPressCallback();  // 移除长按
                ...
                performClick();             // 检查单击
                ...
                break;
            case MotionEvent.ACTION_DOWN:
                ...
                checkForLongClick(0);       // 检测长按
                ...
                break;
            ...
        }
        return true;                        // ◀︎表示事件被消费
    }
    return false;
}

public boolean dispatchTouchEvent(MotionEvent ev) {
    boolean result = false;             // 默认状态为没有消费过

    if (!onInterceptTouchEvent(ev)) {   // 如果没有拦截交给子View
        result = child.dispatchTouchEvent(ev);
    }

    if (!result) {                      // 如果事件没有被消费,询问自身onTouchEvent
        result = onTouchEvent(ev);
    }

    return result;
}

public boolean dispatchTouchEvent(MotionEvent ev) {
  	// 调试用
    if (mInputEventConsistencyVerifier != null) {
        mInputEventConsistencyVerifier.onTouchEvent(ev, 1);
    }

  	// 判断事件是否是针对可访问的焦点视图(很晚才添加的内容，个人猜测和屏幕辅助相关，方便盲人等使用设备)
    if (ev.isTargetAccessibilityFocus() && isAccessibilityFocusedViewOrHost()) {
        ev.setTargetAccessibilityFocus(false);
    }

    boolean handled = false;
    if (onFilterTouchEventForSecurity(ev)) {
        final int action = ev.getAction();
        final int actionMasked = action & MotionEvent.ACTION_MASK;

        // 处理第一次ACTION_DOWN.
        if (actionMasked == MotionEvent.ACTION_DOWN) {
            // 清除之前所有的状态
            cancelAndClearTouchTargets(ev);
            resetTouchState();
        }

        // 检查是否需要拦截.
        final boolean intercepted;
        if (actionMasked == MotionEvent.ACTION_DOWN || mFirstTouchTarget != null) {
            final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
            if (!disallowIntercept) {
                intercepted = onInterceptTouchEvent(ev);	// 询问是否拦截
                ev.setAction(action); 						// 恢复操作，防止被更改
            } else {
                intercepted = false;
            }
        } else {
          	// 没有目标来处理该事件，而且也不是一个新的事件事件(ACTION_DOWN), 进行拦截。
            intercepted = true;
        }

      	// 判断事件是否是针对可访问的焦点视图
        if (intercepted || mFirstTouchTarget != null) {
            ev.setTargetAccessibilityFocus(false);
        }

        // 检查事件是否被取消(ACTION_CANCEL).
        final boolean canceled = resetCancelNextUpFlag(this)
                || actionMasked == MotionEvent.ACTION_CANCEL;

        final boolean split = (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) != 0;
        TouchTarget newTouchTarget = null;
        boolean alreadyDispatchedToNewTouchTarget = false;
      	
      	// 如果没有取消也没有被拦截	(进入事件分发)
        if (!canceled && !intercepted) {

            // 如果事件是针对可访问性焦点视图，我们将其提供给具有可访问性焦点的视图。
          	// 如果它不处理它，我们清除该标志并像往常一样将事件分派给所有的 ChildView。 
            // 我们检测并避免保持这种状态，因为这些事非常罕见。
            View childWithAccessibilityFocus = ev.isTargetAccessibilityFocus()
                    ? findChildWithAccessibilityFocus() : null;

            if (actionMasked == MotionEvent.ACTION_DOWN
                    || (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN)
                    || actionMasked == MotionEvent.ACTION_HOVER_MOVE) {
                final int actionIndex = ev.getActionIndex();
                final int idBitsToAssign = split ? 1 << ev.getPointerId(actionIndex)
                        : TouchTarget.ALL_POINTER_IDS;

                // 清除此指针ID的早期触摸目标，防止不同步。
                removePointersFromTouchTargets(idBitsToAssign);

                final int childrenCount = mChildrenCount;
                if (newTouchTarget == null && childrenCount != 0) {
                    final float x = ev.getX(actionIndex);	// 获取触摸位置坐标
                    final float y = ev.getY(actionIndex);
                    // 查找可以接受事件的 ChildView
                    final ArrayList<View> preorderedList = buildOrderedChildList();
                    final boolean customOrder = preorderedList == null
                            && isChildrenDrawingOrderEnabled();
                    final View[] children = mChildren;
                  	// ▼注意，从最后向前扫描
                    for (int i = childrenCount - 1; i >= 0; i--) {
                        final int childIndex = customOrder
                                ? getChildDrawingOrder(childrenCount, i) : i;
                        final View child = (preorderedList == null)
                                ? children[childIndex] : preorderedList.get(childIndex);

                        // 如果有一个视图具有可访问性焦点，我们希望它首先获取事件，
                      	// 如果不处理，我们将执行正常的分派。 
                      	// 尽管这可能会分发两次，但它能保证在给定的时间内更安全的执行。
                        if (childWithAccessibilityFocus != null) {
                            if (childWithAccessibilityFocus != child) {
                                continue;
                            }
                            childWithAccessibilityFocus = null;
                            i = childrenCount - 1;
                        }

                      	// 检查View是否允许接受事件(即处于显示状态(VISIBLE)或者正在播放动画)
                      	// 检查触摸位置是否在View区域内
                        if (!canViewReceivePointerEvents(child)
                                || !isTransformedTouchPointInView(x, y, child, null)) {
                            ev.setTargetAccessibilityFocus(false);
                            continue;
                        }

                      	// getTouchTarget 中判断了 child 是否包含在 mFirstTouchTarget 中
                      	// 如果有返回 target，如果没有返回 null 
                        newTouchTarget = getTouchTarget(child);
                        if (newTouchTarget != null) {
                            // ChildView 已经准备好接受在其区域内的事件。
                            newTouchTarget.pointerIdBits |= idBitsToAssign;
                            break;	// ◀︎已经找到目标View，跳出循环
                        }

                        resetCancelNextUpFlag(child);
                        if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {
                            mLastTouchDownTime = ev.getDownTime();
                            if (preorderedList != null) {
                                for (int j = 0; j < childrenCount; j++) {
                                    if (children[childIndex] == mChildren[j]) {
                                        mLastTouchDownIndex = j;
                                        break;
                                    }
                                }
                            } else {
                                mLastTouchDownIndex = childIndex;
                            }
                            mLastTouchDownX = ev.getX();
                            mLastTouchDownY = ev.getY();
                            newTouchTarget = addTouchTarget(child, idBitsToAssign);
                            alreadyDispatchedToNewTouchTarget = true;
                            break;
                        }
                      
                        ev.setTargetAccessibilityFocus(false);
                    }
                    if (preorderedList != null) preorderedList.clear();
                }

                if (newTouchTarget == null && mFirstTouchTarget != null) {
                    // 没有找到 ChildView 接收事件
                    newTouchTarget = mFirstTouchTarget;
                    while (newTouchTarget.next != null) {
                        newTouchTarget = newTouchTarget.next;
                    }
                    newTouchTarget.pointerIdBits |= idBitsToAssign;
                }
            }
        }

        // 分发 TouchTarget
        if (mFirstTouchTarget == null) {
            // 没有 TouchTarget，将当前 ViewGroup 当作普通的 View 处理。
            handled = dispatchTransformedTouchEvent(ev, canceled, null,
                    TouchTarget.ALL_POINTER_IDS);
        } else {
            // 分发TouchTarget，如果我们已经分发过，则避免分配给新的目标。 
          	// 如有必要，取消分发。
            TouchTarget predecessor = null;
            TouchTarget target = mFirstTouchTarget;
            while (target != null) {
                final TouchTarget next = target.next;
                if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {
                    handled = true;
                } else {
                    final boolean cancelChild = resetCancelNextUpFlag(target.child)
                            || intercepted;
                    if (dispatchTransformedTouchEvent(ev, cancelChild,
                            target.child, target.pointerIdBits)) {
                        handled = true;
                    }
                    if (cancelChild) {
                        if (predecessor == null) {
                            mFirstTouchTarget = next;
                        } else {
                            predecessor.next = next;
                        }
                        target.recycle();
                        target = next;
                        continue;
                    }
                }
                predecessor = target;
                target = next;
            }
        }

        // 如果需要，更新指针的触摸目标列表或取消。
        if (canceled
                || actionMasked == MotionEvent.ACTION_UP
                || actionMasked == MotionEvent.ACTION_HOVER_MOVE) {
            resetTouchState();
        } else if (split && actionMasked == MotionEvent.ACTION_POINTER_UP) {
            final int actionIndex = ev.getActionIndex();
            final int idBitsToRemove = 1 << ev.getPointerId(actionIndex);
            removePointersFromTouchTargets(idBitsToRemove);
        }
    }

    if (!handled && mInputEventConsistencyVerifier != null) {
        mInputEventConsistencyVerifier.onUnhandledEvent(ev, 1);
    }
    return handled;
}