1.1 dispatchTouchEvent onInterceptTouchEvent onTouchEvent 关系
public boolean dispatchTouchEvent(MotionEvent ev) {
boolean consume = false;
if(onInterceptTouchEvent(ev)) { // 当前view拦截
consume = onTouchEvent(ev);
} else { // 子view分发
child.dispatchTouchEvent(ev);
}
return consume;
}
1.2 PhoneWindow分发到DecorView流程
PhoneWindow2DecorView
2.1 ViewGroup::dispatchTouchEvent
dispatchTouchEvent(MotionEvent ev) {
// 当ACTION_DOWN时，将要重置FLAG_DISALLOW_INTERCEPT标记位；
if (actionMasked == MotionEvent.ACTION_DOWN) {
// 发生ACTION_DOWN事件, 则取消并清除之前所有的触摸targets
cancelAndClearTouchTargets(ev);
resetTouchState(); // 重置触摸状态
}
...
// Check for interception.
final boolean intercepted;
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) { // mFirstTouchTarget 处理事件的子元素
/*
mFirstTouchTarget != null , 则由子元素处理，
否则，需要由 当前group处理，
*/
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
// 滑动冲突 内部拦截法：通过改变 FLAG_DISALLOW_INTERCEPT 设置ViewGroup是否拦截事件；
if (!disallowIntercept) {
intercepted = onInterceptTouchEvent(ev);
ev.setAction(action); // restore action in case it was changed
} else {
intercepted = false;
}
} else {
// There are no touch targets and this action is not an initial down
// so this view group continues to intercept touches.
intercepted = true;
}
....
// 当前viewgrop不拦截，且Action未取消
if (!canceled && !intercepted) {
...
// 遍历子元素分发
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);
// 如果当前视图无法获取用户焦点，则跳过本次循环
if (childWithAccessibilityFocus != null) {...}
//如果view不可见，或者触摸的坐标点不在view的范围内，则跳过本次循环
if (!canViewReceivePointerEvents(child)
|| !isTransformedTouchPointInView(x, y, child, null)) {
...
}
// 已经开始接收触摸事件,并退出整个循环
newTouchTarget = getTouchTarget(child);
if (newTouchTarget != null) {
...
}
//重置取消或抬起标志位
//如果触摸位置在child的区域内，则把事件分发给子View或ViewGroup
resetCancelNextUpFlag(child);
// 递归调用子view的dispatchTouchEvent
if (dispatchTransformedTouchEvent(ev, false, child/*存在子元素*/, idBitsToAssign)) { //2.2
// Child wants to receive touch within its bounds.
mLastTouchDownTime = ev.getDownTime();
if (preorderedList != null) {
// childIndex points into presorted list, find original index
for (int j = 0; j < childrenCount; j++) {
if (children[childIndex] == mChildren[j]) {
mLastTouchDownIndex = j;
break;
}
}
} else {
mLastTouchDownIndex = childIndex;
}
mLastTouchDownX = ev.getX();
mLastTouchDownY = ev.getY();
//如果child处理事件，则添加到mFirstTouchTarget单链表
newTouchTarget = addTouchTarget(child, idBitsToAssign); //2.3
alreadyDispatchedToNewTouchTarget = true;
break;
}
...
}
...
//
if (mFirstTouchTarget == null) {
//子view未消耗事件，则mFirstTouchTarget null, 由当前ViewGroup来处理
handled = dispatchTransformedTouchEvent(ev, canceled, null, TouchTarget.ALL_POINTER_IDS); //2.2
} else {
...
if (dispatchTransformedTouchEvent(ev, cancelChild, target.child, target.pointerIdBits)) {
handled = true; // 2.2 target.child处理
}
...
}
}
if (mFirstTouchTarget == null) { // 无子元素处理事件时；
handled = dispatchTransformedTouchEvent(ev, canceled, null/*会调用view.dispatchTouchEvent*/, TouchTarget.ALL_POINTER_IDS); //2.2
} else {
...//如果View消费ACTION_DOWN事件，那么MOVE,UP等事件相继开始执行
}
}
2.2 ViewGroup::dispatchTransformedTouchEvent
private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,
View child, int desiredPointerIdBits) {
...
if (child == null) {
handled = super.dispatchTouchEvent(event); // 返回父组件继续dispatchTouchEvent
// 最终传递给View处理 参考 View 对事件的处理过程
// 不存在子视图时，ViewGroup调用View.dispatchTouchEvent分发事件，再调用ViewGroup.onTouchEvent来处理事件
} else {
handled = child.dispatchTouchEvent(event); // 子节点 (View //2.4 ViewGroup//2.1) 分发事件
}
...
}
2.3 ViewGroup::addTouchTarget
只有处理ActionDown事件，才会进入addTouchTarget, mFirstTouchTarget被赋值；
private TouchTarget addTouchTarget(View child, int pointerIdBits) {
TouchTarget target = TouchTarget.obtain(child, pointerIdBits);
target.next = mFirstTouchTarget;
mFirstTouchTarget = target; // mFirstTouchTarget 获取 TouchTarget
return target;
}
2.4 View::dispatchTouchEvent
public boolean dispatchTouchEvent(MotionEvent event) {
...
if (onFilterTouchEventForSecurity(event)) {
//noinspection SimplifiableIfStatement
ListenerInfo li = mListenerInfo;
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) { //onTouch 优先处理
result = true;
}
if (!result && onTouchEvent(event)) { //onTouchEvent
result = true; // onTouchEvent
}
...
}
2.5 ViewGroup::dispatchTouchEvent 概览
ViewGroup_dispatchTouchEvent
3.1 Android 滑动冲突
3.1.1 外部拦截法
viewgrop 中重写 onInterceptTouchEvent
public boolean onInterceptTouchEvent(MotionEvent ev) {
boolean result = false;
detector.onTouchEvent(ev); // 事件传递给 GestureDetector
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
downX = ev.getX();
downY = ev.getY();
break;
case MotionEvent.ACTION_MOVE:
// 新坐标
float newdownX = ev.getX();
float newdownY = ev.getY();
// 计算距离
int distanceX = (int) Math.abs(newdownX - downX);
int distanceY = (int) Math.abs(newdownY - downY);
// distanceX 防止抖动
if(distanceX > distanceY && distanceX > 10) // 根据dx dy判断水平 垂直方向滑动
result = true;
else
scrollToPager(currentIndex);
break;
case MotionEvent.ACTION_UP:
break;
}
return result;
}
3.1.2 内部拦截法
public boolean onTouchEvent(MotionEvent event) {
getParent().requestDisallowInterceptTouchEvent(true); // 设置父组件(listview)不拦截事件
}