觸摸事件分發(fā)的源碼分析，base On aosp 25
Activity.java
/**
*處理觸摸屏幕事件。你可以覆寫該方法去截獲觸摸屏幕事件，在這些事件
*分發(fā)給窗口之前。確認這個調(diào)用可以使觸摸事件正常的被處理
*
* @param ev 屏幕觸摸事件
*
* @return boolean 返回true,代表事件被消費
*/
public boolean dispatchTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
onUserInteraction();
}
//window是PhoneWinow
//superDispatchTouchEvent(ev) 將調(diào)用 mDecor.dispatchTouchEvent
//調(diào)用后的結(jié)果掉膘事件消費的結(jié)果
if (getWindow().superDispatchTouchEvent(ev)) {
return true;
}
return onTouchEvent(ev);
}
以下是對上面的補充。
Activity.java
mWindow = new PhoneWindow(this, window);
PhoneWindow.java
@Override
public boolean superDispatchTouchEvent(MotionEvent event) {
//實際上是ViewGroup.dispatchTouchEvent(MotionEvent ev)
return mDecor.superDispatchTouchEvent(event);
}
ViewGourp.java
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
省去部分代碼
boolean handled = false;
if (onFilterTouchEventForSecurity(ev)) {
final int action = ev.getAction();
final int actionMasked = action & MotionEvent.ACTION_MASK;
//每個事件都是由down事件開始
// 處理開始的 down 事件
if (actionMasked == MotionEvent.ACTION_DOWN) {
// 當開始一個的手勢動作的時候 拋棄之前所有的狀態(tài)
// 拋棄之前 事件的 cancle 與 up 事件
cancelAndClearTouchTargets(ev);
resetTouchState();
}
//檢查攔截的情況
final boolean intercepted;
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
//如果disallowIntercept 為false;
if (!disallowIntercept) {
//調(diào)用攔截函數(shù)，獲取intercepted 狀態(tài)
intercepted = onInterceptTouchEvent(ev);
ev.setAction(action); // restore action in case it was changed
} else {
intercepted = false;
}
} else {
//沒有 touch targets 同時down 事件沒有初始化，ViewGroup繼續(xù)攔截觸摸
intercepted = true;
}
// 如果攔截了, 開始正常事件的分發(fā)。
// 同時如果有一個view已經(jīng)開始處理手勢，也開始正常事件的分發(fā)
if (intercepted || mFirstTouchTarget != null) {
//設置目標獲取焦點的狀態(tài)為 false, native 方法。
//AccessibilityFocus accessibility services 的一個東東
ev.setTargetAccessibilityFocus(false);
}
// 檢查取消的情況
final boolean canceled = resetCancelNextUpFlag(this)
|| actionMasked == MotionEvent.ACTION_CANCEL;
//如果有必要，更新 鏈表touch targets中poninter down。
final boolean split = (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) != 0;
TouchTarget newTouchTarget = null;
boolean alreadyDispatchedToNewTouchTarget = false;
// 下面是在 canceled 與 intercepted 為false的時候
if (!canceled && !intercepted) {
// If the event is targeting accessiiblity focus we give it to the
// view that has accessibility focus and if it does not handle it
// we clear the flag and dispatch the event to all children as usual.
// We are looking up the accessibility focused host to avoid keeping
// state since these events are very rare.
//AccessibilityFocus accessibility services 的一個東東
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(); // always 0 for down
final int idBitsToAssign = split ? 1 << ev.getPointerId(actionIndex)
: TouchTarget.ALL_POINTER_IDS;
// Clean up earlier touch targets for this pointer id in case they
// have become out of sync.
removePointersFromTouchTargets(idBitsToAssign);
final int childrenCount = mChildrenCount;
if (newTouchTarget == null && childrenCount != 0) {
final float x = ev.getX(actionIndex);
final float y = ev.getY(actionIndex);
// Find a child that can receive the event.
// Scan children from front to back.
final ArrayList<View> preorderedList = buildTouchDispatchChildList();
final boolean customOrder = preorderedList == null
&& isChildrenDrawingOrderEnabled();
final View[] children = mChildren;
for (int i = childrenCount - 1; i >= 0; i--) {
final int childIndex = getAndVerifyPreorderedIndex(
childrenCount, i, customOrder);
final View child = getAndVerifyPreorderedView(
preorderedList, children, childIndex);
// If there is a view that has accessibility focus we want it
// to get the event first and if not handled we will perform a
// normal dispatch. We may do a double iteration but this is
// safer given the timeframe.
if (childWithAccessibilityFocus != null) {
if (childWithAccessibilityFocus != child) {
continue;
}
childWithAccessibilityFocus = null;
i = childrenCount - 1;
}
if (!canViewReceivePointerEvents(child)
|| !isTransformedTouchPointInView(x, y, child, null)) {
ev.setTargetAccessibilityFocus(false);
continue;
}
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;
}
// The accessibility focus didn't handle the event, so clear
// the flag and do a normal dispatch to all children.
ev.setTargetAccessibilityFocus(false);
}
if (preorderedList != null) preorderedList.clear();
}
if (newTouchTarget == null && mFirstTouchTarget != null) {
// Did not find a child to receive the event.
// Assign the pointer to the least recently added target.
newTouchTarget = mFirstTouchTarget;
while (newTouchTarget.next != null) {
newTouchTarget = newTouchTarget.next;
}
newTouchTarget.pointerIdBits |= idBitsToAssign;
}
}
}
// 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;
}
}
// Update list of touch targets for pointer up or cancel, if needed.
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;
}
/**
* 取消與清除 touch targets 這個單鏈表數(shù)據(jù)
* Cancels and clears all touch targets. 將mFirstTouchTarget設置為null
*/
private void cancelAndClearTouchTargets(MotionEvent event) {
//如果是第一次觸發(fā)down mFirstTouchTarget == null
if (mFirstTouchTarget != null) {
boolean syntheticEvent = false;
if (event == null) {
final long now = SystemClock.uptimeMillis();
event = MotionEvent.obtain(now, now,
MotionEvent.ACTION_CANCEL, 0.0f, 0.0f, 0);
event.setSource(InputDevice.SOURCE_TOUCHSCREEN);
syntheticEvent = true;
}
for (TouchTarget target = mFirstTouchTarget; target != null; target = target.next) {
resetCancelNextUpFlag(target.child);
dispatchTransformedTouchEvent(event, true, target.child, target.pointerIdBits);
}
clearTouchTargets();
if (syntheticEvent) {
event.recycle();
}
}
}
傳遞（遍歷） 觸摸事件
/**
* 傳遞觸摸事件給子控件
* 去掉無效點的ID, 有必要的話覆些事件處理.
*如果child 是空的,MotionEvent 會被發(fā)給 這個 ViewGroup 替代處理.
*/
private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,
View child, int desiredPointerIdBits) {
final boolean handled;
// 取消action是一個特別的案例。不必處理傳遞與過濾。重要的分時是action
//不是內(nèi)容。
//簡單的說當傳入 cancle 是true 或者action is MotionEvent.ACTION_CANCEL
//的時候我們處理掉，然后return。
final int oldAction = event.getAction();
if (cancel || oldAction == MotionEvent.ACTION_CANCEL) {
event.setAction(MotionEvent.ACTION_CANCEL);
if (child == null) {
handled = super.dispatchTouchEvent(event);
} else {
handled = child.dispatchTouchEvent(event);
}
event.setAction(oldAction);
return handled;
}
// 計算需要投遞的 pointer 的個數(shù)
final int oldPointerIdBits = event.getPointerIdBits();
final int newPointerIdBits = oldPointerIdBits & desiredPointerIdBits;
// 如果由于一些原因我們結(jié)束了一個不可靠的狀態(tài)，
//這個狀態(tài)看起來可能產(chǎn)生一個觸摸事件但是又沒觸摸點
//我們將丟掉這個事件。就是return false
if (newPointerIdBits == 0) {
return false;
}
//如果觸摸點數(shù)是一樣的并且我們沒有必要去處理任何不可逆轉(zhuǎn)的傳遞，
//然后我們可以重用運動事件，對于本次事件分發(fā)，我們竟可能的小心revert任何我們做出改變
//否者我們需要創(chuàng)建一個副本。
//分發(fā)事件
final MotionEvent transformedEvent;
if (newPointerIdBits == oldPointerIdBits) {
if (child == null || child.hasIdentityMatrix()) {
if (child == null) {
//如果沒有子View，調(diào)用view. dispatchTouchEvent 來處理自己dispatchTouchEvent
handled = super.dispatchTouchEvent(event);
} else {
//存在子View
//坐標系的變化
//算出子view相對于左上角的位移
final float offsetX = mScrollX - child.mLeft;
final float offsetY = mScrollY - child.mTop;
event.offsetLocation(offsetX, offsetY);
//調(diào)用子view的dispatchTouchEvent
handled = child.dispatchTouchEvent(event);
event.offsetLocation(-offsetX, -offsetY);
}
return handled;
}
transformedEvent = MotionEvent.obtain(event);
} else {
transformedEvent = event.split(newPointerIdBits);
}
//處理必要的轉(zhuǎn)移與分發(fā)
// Perform any necessary transformations and dispatch.
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.java
/**
* Pass the touch screen motion event down to the target view, or this
* view if it is the target.
*
* @param event The motion event to be dispatched.
* @return True if the event was handled by the view, false otherwise.
*/
public boolean dispatchTouchEvent(MotionEvent event) {
// If the event should be handled by accessibility focus first.
if (event.isTargetAccessibilityFocus()) {
// We don't have focus or no virtual descendant has it, do not handle the event.
if (!isAccessibilityFocusedViewOrHost()) {
return false;
}
// We have focus and got the event, then use normal event dispatch.
event.setTargetAccessibilityFocus(false);
}
boolean result = false;
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onTouchEvent(event, 0);
}
final int actionMasked = event.getActionMasked();
if (actionMasked == MotionEvent.ACTION_DOWN) {
// Defensive cleanup for new gesture
stopNestedScroll();
}
if (onFilterTouchEventForSecurity(event)) {
if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {
result = true;
}
//noinspection SimplifiableIfStatement
ListenerInfo li = mListenerInfo;
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
result = true;
}
if (!result && onTouchEvent(event)) {
result = true;
}
}
if (!result && mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onUnhandledEvent(event, 0);
}
// Clean up after nested scrolls if this is the end of a gesture;
// also cancel it if we tried an ACTION_DOWN but we didn't want the rest
// of the gesture.
if (actionMasked == MotionEvent.ACTION_UP ||
actionMasked == MotionEvent.ACTION_CANCEL ||
(actionMasked == MotionEvent.ACTION_DOWN && !result)) {
stopNestedScroll();
}
return result;
}
