当触摸事件发生时，Activity先接受到事件。
public boolean dispatchTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
//在Activity可以实现该方法，处理必要的逻辑
//当此activity在栈顶时，触屏点击按home，back，menu键等都会触发此方法
onUserInteraction();
}
// 若返回true
if (getWindow().superDispatchTouchEvent(ev)) {
//1. 获取到的是window的唯一实现类PhoneWindow;
//2.该方法由其唯一子类PhoneWindow类实现，
// 3.PhoneWindow内部有DecorWindow类，其继承自FrameLayout，是所有界面的父类，
//4.FrameLayout继承自ViewGroup类，最终调用到ViewGroup的super.dispatchTouchEvent(event);
//实现从Activity到内部View的传递，即内部可优先处理事件，若未true，再由Activity处理。
return true;
}
// 否则：继续往下调用Activity.onTouchEvent
return onTouchEvent(ev);
DecorView内的dispatchToucEvent（可以通过Activity内的onTouchEvent打开DecorView）
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
final Window.Callback cb = mWindow.getCallback();
//cb.dispatchTouchEvent(ev) :调用Activity的dispatchTouchEvent（）
// super.dispatchTouchEvent(ev):交给ViewGroup处理。
return cb != null && !mWindow.isDestroyed() && mFeatureId < 0
? cb.dispatchTouchEvent(ev) : super.dispatchTouchEvent(ev);
关于Activity的内的onTouchEvent
最后当触摸屏事件未被其下的任何视图处理时调用，这对于处理发生在窗口边界之外的触摸事件非常有用，因为在那里没有接收它的视图。
public boolean onTouchEvent(MotionEvent event) {
//处理发生在Window边界外的触摸事件。
if (mWindow.shouldCloseOnTouch(this, event)) {
finish();
return true;
}
return false;
}
// 主要是对于处理边界外点击事件的判断：是否是DOWN事件，event的坐标是否在边界内等
public boolean shouldCloseOnTouch(Context context, MotionEvent event) {
if (mCloseOnTouchOutside && event.getAction() == MotionEvent.ACTION_DOWN
&& isOutOfBounds(context, event) && peekDecorView() != null) {
//说明事件在边界外，消费事件
return true;
}
回到getWindow().superDispatchTouchEvent(ev)向内ViewGroup内传递的分析。
ViewGroup内dispatchTouchEvent
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onTouchEvent(ev, 1);
}
//如果事件以可访问且可聚焦的view为目标，则启动正常事件调度。否则交给子view处理点击。
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;
// Handle an initial down.
if (actionMasked == MotionEvent.ACTION_DOWN) {
//当开始一个新的触摸手势时，删除原先的状态。
//重置状态，（由于应用程序切换、ANR或其他一些状态改变，底层可能已经取消事件）
cancelAndClearTouchTargets(ev);
resetTouchState();
}
//判断是否被打断
final boolean intercepted;
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
//判断值1：disallowIntercept = 是否禁用事件拦截的功能(默认是false)，
//可通过调用requestDisallowInterceptTouchEvent（）修改
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
if (!disallowIntercept) {
// 对onInterceptTouchEvent()返回值取反
// a. 若在onInterceptTouchEvent()中返回false（即不拦截事件）,则为true
intercepted = onInterceptTouchEvent(ev);
ev.setAction(action);
} else {
// b. 若在onInterceptTouchEvent()中返回true（即拦截事件），则为false，
intercepted = false;
}
} else {
intercepted = true;
}
//.......此处省略部分代码
final boolean split = (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) != 0;
TouchTarget newTouchTarget = null;
boolean alreadyDispatchedToNewTouchTarget = false;
if (!canceled && !intercepted) {
View childWithAccessibilityFocus = ev.isTargetAccessibilityFocus()
? findChildWithAccessibilityFocus() : null;
if (actionMasked == MotionEvent.ACTION_DOWN
|| (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN)
|| actionMasked == MotionEvent.ACTION_HOVER_MOVE) {
//.......此处省略部分代码
final int childrenCount = mChildrenCount;
if (newTouchTarget == null && childrenCount != 0) {
final float x = ev.getX(actionIndex);
final float y = ev.getY(actionIndex);
final ArrayList<View> preorderedList = buildTouchDispatchChildList();
final boolean customOrder = preorderedList == null
&& isChildrenDrawingOrderEnabled();
final View[] children = mChildren;
//遍历所有的子view，寻找可以传递事件的view
for (int i = childrenCount - 1; i >= 0; i--) {
final int childIndex = getAndVerifyPreorderedIndex(
childrenCount, i, customOrder);
final View child = getAndVerifyPreorderedView(
preorderedList, children, childIndex);
//如果找到一个可达且可获取焦点的view，让其先获得事件，
//如果没有处理，执行异常调度。在在给定的时间范围内，进行双重迭代，这是比较安全的。
if (childWithAccessibilityFocus != null) {
if (childWithAccessibilityFocus != child) {
continue;
}
childWithAccessibilityFocus = null;
i = childrenCount - 1;
}
if (!canViewReceivePointerEvents(child)
|| !isTransformedTouchPointInView(x, y, child, null)) {
ev.setTargetAccessibilityFocus(false);
continue;
}
//.......此处省略部分代码
resetCancelNextUpFlag(child);
//将事件转换成特定子view的坐标空间，过滤掉无关的指针ID，并在必要时重写其事件。
//如果子view为空，事件将转交给其父类处理。
if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {
//将事件分发给子view
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;
}
//此处省略N行........
}
if (preorderedList != null) preorderedList.clear();
}
//mFirstTouchTarget:触摸目标链表中的第一次触摸目标。
if (newTouchTarget == null && mFirstTouchTarget != null) {
//若没有找到可以传递事件的子view，将指针分配到最近最少添加的view。
newTouchTarget = mFirstTouchTarget;
while (newTouchTarget.next != null) {
newTouchTarget = newTouchTarget.next;
}
newTouchTarget.pointerIdBits |= idBitsToAssign;
}
}
}
if (mFirstTouchTarget == null) {
// No touch targets so treat this as an ordinary view.
handled = dispatchTransformedTouchEvent(ev, canceled, null,
TouchTarget.ALL_POINTER_IDS);
} else {
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;
}
//此处省略N行........
}
predecessor = target;
target = next;
}
}
// Update list of touch targets for pointer up or cancel, if needed.
//此处省略N行........
return handled;
}
前面判断完分发条件后，对可以获取的view分发事件，主要是通过以下方法：
private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,
View child, int desiredPointerIdBits) {
final boolean handled;
final int oldAction = event.getAction();
if (cancel || oldAction == MotionEvent.ACTION_CANCEL) {
event.setAction(MotionEvent.ACTION_CANCEL);
if (child == null) {
//若子view为null，执行其父view的dispatchTouchEvent
handled = super.dispatchTouchEvent(event);
} else {
//若不为null，则传递事件。
handled = child.dispatchTouchEvent(event);
}
event.setAction(oldAction);
return handled;
}
// 计算要传递的指针的数量。
final int oldPointerIdBits = event.getPointerIdBits();
final int newPointerIdBits = oldPointerIdBits & desiredPointerIdBits;
//可能会产生一个没有指针数的事件,那么放弃该事件。
if (newPointerIdBits == 0) {
return false;
}
//如果指针的数目是相同的，并且不需要执行任何不可逆的转换，
//则恢复之前所做的更改，以重用这个调度的事件。
//否则需要复印一份。
final MotionEvent transformedEvent;
if (newPointerIdBits == oldPointerIdBits) {
if (child == null || child.hasIdentityMatrix()) {
if (child == null) {
handled = super.dispatchTouchEvent(event);
} else {
final float offsetX = mScrollX - child.mLeft;
final float offsetY = mScrollY - child.mTop;
event.offsetLocation(offsetX, offsetY);
handled = child.dispatchTouchEvent(event);
event.offsetLocation(-offsetX, -offsetY);
}
return handled;
}
transformedEvent = MotionEvent.obtain(event);
} else {
transformedEvent = event.split(newPointerIdBits);
}
if (child == null) {
handled = super.dispatchTouchEvent(transformedEvent);
} else {
final float offsetX = mScrollX - child.mLeft;
final float offsetY = mScrollY - child.mTop;
transformedEvent.offsetLocation(offsetX, offsetY);
if (! child.hasIdentityMatrix()) {
transformedEvent.transform(child.getInverseMatrix());
}
handled = child.dispatchTouchEvent(transformedEvent);
}
// Done.
transformedEvent.recycle();
return handled;
}
View内的dispatchTouchEvent
public boolean dispatchTouchEvent(MotionEvent event) {
// 如果事件可被可达到且的焦点view处理
if (event.isTargetAccessibilityFocus()) {
if (!isAccessibilityFocusedViewOrHost()) {
return false;
}
// view有焦点，且获得到事件处理
event.setTargetAccessibilityFocus(false);
}
boolean result = false;
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onTouchEvent(event, 0);
}
final int actionMasked = event.getActionMasked();
if (actionMasked == MotionEvent.ACTION_DOWN) {
stopNestedScroll();
}
if (onFilterTouchEventForSecurity(event)) {
//条件1：(mViewFlags & ENABLED_MASK) == ENABLED
//a. 该条件是判断当前点击的view是否enable
// b. 由于很多View默认enable，故该条件恒定为true
//条件2：handleScrollBarDragging(event)，事件是否是拖动滚动条
if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {
result = true;
}
// 说明：只有以下3个条件都为真，dispatchTouchEvent()才返回true；否则执行onTouchEvent()
// 1. mOnTouchListener != null： 是否注册触摸监听
// 2. (mViewFlags & ENABLED_MASK) == ENABLED： 当前被点击的view是否enable
// 3. mOnTouchListener.onTouch(this, event) ：监听的boolean类型回调值是否是true
ListenerInfo li = mListenerInfo;
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
//符合条件，未被打断，则事件分发结束
result = true;
}
//若为fasle，调用view的onTouchEvent（）方法处理事件。
if (!result && onTouchEvent(event)) {
result = true;
}
}
//此处省略N行代码..........
return result;
}
再看onTouchEvent方法()
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) {
//如当前view的状态是disable的
if (action == MotionEvent.ACTION_UP && (mPrivateFlags & PFLAG_PRESSED) != 0) {
setPressed(false);
}
return (((viewFlags & CLICKABLE) == CLICKABLE
|| (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)
|| (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE);
}
if (mTouchDelegate != null) {
//如果TouchDelegate对象不为空，将事件传递给它处理，不再往下。
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:
//手指抬起action
boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != 0;
if ((mPrivateFlags & PFLAG_PRESSED) != 0 || prepressed) {
//如果view没有获取焦点，为其请求焦点
boolean focusTaken = false;
if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {
focusTaken = requestFocus();
}
if (prepressed) {
setPressed(true, x, y);
}
if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) {
removeLongPressCallback();
if (!focusTaken) {
if (mPerformClick == null) {
mPerformClick = new PerformClick();
}
//执行点击事件
if (!post(mPerformClick)) {
performClick();
}
}
}
//此处省略N行代码......
break;
case MotionEvent.ACTION_DOWN:
mHasPerformedLongPress = false;
if (performButtonActionOnTouchDown(event)) {
break;
}
//此处省略N行........
if (isInScrollingContainer) {
//此处省略N行........
postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout());
} else {
setPressed(true, x, y);
//判断是不是长按
checkForLongClick(0, x, y);
}
break;
case MotionEvent.ACTION_CANCEL:
//此处省略N行........
break;
case MotionEvent.ACTION_MOVE:
//此处省略N行........
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;
}
网友评论