在Android-27中查看源码：
在看完View源码的触摸事件(View源码-Touch事件)后，我们接着来看看容器类View的触摸事件。因为容器类的View都继承自ViewGroup，所以我们在ViewGroup的源码中来看看是如何处理触摸事件的。
同样的先来看ViewGroup源码中的dispatchTouchEvent方法：
final boolean intercepted;
if (actionMasked == MotionEvent.ACTION_DOWN || mFirstTouchTarget != null) {
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
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;
}首先，会判断是否不允许拦截，可以通过requestDisallowInterceptTouchEvent进行设置，默认允许拦截。如果允许拦截，会调用onInterceptTouchEvent，看看该View是否拦截了触摸事件，默认不拦截即可以将触摸事件向子View传递。
接下来，如果触摸事件没有取消并且没有拦截，在手指按下的时候：
final ArrayList<View> preorderedList = buildTouchDispatchChildList();
...
for (int i = childrenCount - 1; i >= 0; i--){
...
newTouchTarget = getTouchTarget(child);
if (newTouchTarget != null) {
// Child is already receiving touch within its bounds.
// Give it the new pointer in addition to the ones it is handling.
newTouchTarget.pointerIdBits |= idBitsToAssign;
break;
}
resetCancelNextUpFlag(child);
if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {
// 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();
newTouchTarget = addTouchTarget(child, idBitsToAssign);
alreadyDispatchedToNewTouchTarget = true;
break;
}
...
}- 按照绘制子View的顺序，找到该ViewGoup的所有子view，并保存到ArrayList中。
- 根据视图顺序依次遍历子View。判断当前子view是否是TouchTarget，若是则跳出循环。否则调用dispatchTransformedTouchEvent方法，如果当前子View的dispatchTouchEvent返回为true,找到该子View在ViewGroup中的index,并将该子View作为新的TouchTarget。
- 清楚保存了所有子View的ArrayList。
然后在TouchTarget形成的链式结构中，处理触摸事件：
// Dispatch to touch targets.
if (mFirstTouchTarget == null) {
// No touch targets so treat this as an ordinary view.
handled = dispatchTransformedTouchEvent(ev, canceled, null,TouchTarget.ALL_POINTER_IDS);
} else {
// Dispatch to touch targets, excluding the new touch target if we already
// dispatched to it. Cancel touch targets if necessary.
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;
}
}- 如果子View没有处理触摸事件，则由当前的ViewGroup处理，然后返回处理结果。因为ViewGroup是View的子类，所以还是由View的dispatchTouchEvent处理。
- 如果子View中处理了触摸事件，根据TouchTarget生成的链式结构，不断循环，分别调用里面View的dispatchTouchEvent方法。
从上面的分析可以看出整个ViewGroup的Touch事件的整个传递过程如下：
- 是否调用了requestDisallowInterceptTouchEvent方法设置不允许拦截，默认允许拦截。若允许拦截，则再调用onInterceptTouchEvent,看是否拦截。
- 如果触摸事件被拦截，则调用ViewGroup的dispatchTransformedTouchEvent方法，其实是调用View的dispatchTouchEvent方法。否则继续向下。
-
当触摸事件为MotionEvent.ACTION_DOWN时，首先获取根据绘制顺序保存了所有子View的ArrayLsit，然后再根据视图顺序去遍历子View。
- 如果从TouchTarget形成的链表中发现该View,则跳出循环，即找到了TouchTarget。否则继续向下。
- 在子View中寻找，当子View的dispatchTouchEvent方法返回为true时,则找到了新的TouchTarget，并将其添加到TouchTarget形成的链表中。
- 遍历TouchTarget形成的链表，然后对链表里面的子View分别调用dispatchTouchEvent，最后将处理结果返回。
