事件分發
入口點爲Activity中的dispatchTouchEvent(MotionEvent ev)
public boolean dispatchTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
onUserInteraction();
}
//這個window我們知道是PhoneWindow,那就直接去PhoneWindow吧
if (getWindow().superDispatchTouchEvent(ev)) {
return true;
}
//默認返回時false
return onTouchEvent(ev);
}
PhoneWindow
@Override
public boolean superDispatchTouchEvent(MotionEvent event) {
//調用了decorView的這個方法，我們知道，它一定開始要去View中開始搞事情了。
//最後調用了ViewGroup的dispatchTouchEvent(MotionEvent event)
return mDecor.superDispatchTouchEvent(event);
}
ViewGroup
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
if (onFilterTouchEventForSecurity(ev)) {
final int action = ev.getAction();
final int actionMasked = action & MotionEvent.ACTION_MASK;
//處理down事件
// Handle an initial down.
if (actionMasked == MotionEvent.ACTION_DOWN) {
//因爲是down事件，作爲一次新事件的開頭，清除上次的標誌、緩存
cancelAndClearTouchTargets(ev);
resetTouchState();
}
//檢測事件攔截
// Check for interception.
final boolean intercepted;
//Down事件發生的時候 mFirstTouchTarget == null
// Up和Move的時候，mFirstTouchTarget如果在down時找到了消費的那個，mFirstTouchTarget!=null
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
//是否不允許攔截？
//默認MGroupFlags值是0 ,disallowIntercept爲false ,表示允許攔截
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
if (!disallowIntercept) {
//允許攔截
intercepted = onInterceptTouchEvent(ev);
ev.setAction(action); // restore action in case it was changed
} else {
//不允許攔截
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;
}
########## down判斷完之後下面的這個if有點長
//非攔截也非取消信號
if (!canceled && !intercepted) {
//下面爲ACTION_DOWN的處理
##### ActionDown纔會執行的，找目標~~~
if (actionMasked == MotionEvent.ACTION_DOWN
|| (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN)
|| actionMasked == MotionEvent.ACTION_HOVER_MOVE) {
final int childrenCount = mChildrenCount;
if (newTouchTarget == null && childrenCount != 0) {
final float x = ev.getX(actionIndex);
final float y = ev.getY(actionIndex);
//更具view.getZ()的值，來創建這個View集合
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);
// canReceivePointerEvents檢測了當前這個View的可見性是否是Visible
// isTransformedTouchPointInView檢測了位置是否在該區域
if (!child.canReceivePointerEvents()
|| !isTransformedTouchPointInView(x, y, child, null)) {
ev.setTargetAccessibilityFocus(false);
//不可見及位置不合適都繼續尋找
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);
//當前View可見又在區域,View是否要處理這個事件？
//當然是分發給他
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;
//已經找到一個，並且返回了true消費了當前事件
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();
}
//上面如果找到了一個View並且在返回了true,那麼這裏不會執行
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;
}
}
#####
}
########## 非取消，也非攔截的邏輯
-
接着往下
// Dispatch to touch targets. if (mFirstTouchTarget == null) { //沒有找到孩子來搞事情 // No touch targets so treat this as an ordinary view. handled = dispatchTransformedTouchEvent(ev, canceled, null, TouchTarget.ALL_POINTER_IDS); } else { //分發事件到目標 // 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) { //up時重置mFirstTouchTarget等 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); } //返回handled,標緻結束 return handled;}
ACTION DOWN的時候，主要是要找到目標View(即位置在範圍內，並且可見性爲Visible的)，而且它的目標是找到一個消費事件的View,加入進mFirstTouchTarget這個鏈表，這樣，當下次事件：Move、Up事件來到的時候，就直接從mFirstTouchTaget取出這個目標View，直接調用dispatchTransformedTouchEvent進行事件分發。也就是一個View,如果在Down事件發生的時候，返回了false,不處理，那麼後續的Move和Up事件都不會接收到。
dispatchTransformedTouchEvent
private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,
View child, int desiredPointerIdBits) {
handled = child.dispatchTouchEvent(transformedEvent);
return handled;
}
火速進入View的dispatchTouchEvent
public boolean dispatchTouchEvent(MotionEvent event) {
final int actionMasked = event.getActionMasked();
if (actionMasked == MotionEvent.ACTION_DOWN) {
//如果是ActionDown那麼停下滾動
stopNestedScroll();
}
if (onFilterTouchEventForSecurity(event)) {
if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {
result = true;
}
// 調用了onTouch()
ListenerInfo li = mListenerInfo;
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
result = true;
}
//如果該View有設置onTouch事件，那麼onTouchEvent就不會被回調是這樣的嗎？我們試試就知道
###確實是這樣的，設置了onTouch那麼onTouchEvent就不會被調用了
if (!result && onTouchEvent(event)) {
result = true;
}
}
}
onTouchEvent()
switch (action) {
case MotionEvent.ACTION_UP:
if (prepressed) {
//擡起時設置動畫效果
setPressed(true, x, y);}
//沒有設置長按監聽
if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) {
// This is a tap, so remove the longpress check
removeLongPressCallback();
// Only perform take click actions if we were in the pressed state
if (!focusTaken) {
// Use a Runnable and post this rather than calling
// performClick directly. This lets other visual state
// of the view update before click actions start.
if (mPerformClick == null) {
mPerformClick = new PerformClick();
}
//使用Handler發消息的方式觸發onClick,而非直接調用，相當於就是留一些時間
if (!post(mPerformClick)) {
performClickInternal();
}
}
上面就在Up事件裏面主要調用了onclick的回調(使用Handler進行)，同時還有Down事件，主要時判斷有沒有監聽長按事件，如果有，發送一個延時的消息，看了下默認時500ms，根據配置來獲得。
事件攔截問題：
- 幾個方法：
- dispatchTouchEvent() View和ViewGroup共有
- onInterceptTouchEvent() ViewGroup特有
- requestDisallowInterceptTouchEvent() 用於子View 這個方法名的意思： 不攔截！！不攔截！！記住
down事件很重要，是否能找到可以分發的子View，完全是在Down事件中進行查找，如果當前ViewGroup的包含的View都返回false,那麼mFistTouchTarget爲空，遊戲結束。後續傳來的Move和Up都不會收到。該次事件分發給ViewGroup的onTouchEvent處理。如果有子View的Down返回的是true,那麼mFirstTouchTarget指向該View,遊戲繼續進行，後續Move和Up進入：是否有請求不攔截，
沒有例子的學習都是耍流氓，ok
//繼承LinearLayout
<com.yp.deepstudy.MyLinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/colorPrimary"
android:gravity="center"
android:orientation="vertical">
//繼承自View
<com.yp.deepstudy.MyView
android:layout_width="120dp"
android:layout_height="120dp"
android:background="@color/colorAccent" />
</com.yp.deepstudy.MyLinearLayout>
-
按下擡起、按下移動擡起，因爲down事件都返回的是false，沒人處理，所以後續Move和Up都接收不到
// 0代表 down事件 MyLinearLayout: dispatchTouchEvent0 MyLinearLayout: onInterceptTouchEvent0 MyView: dispatchTouchEvent0 MyView: onTouchEvent0 MyLinearLayout: onTouchEvent0 -
現在將MyView，的dispatchTouchEvent改成返回true:下面的log表明有控件進行消費（Down中返回true，如果在move中返回true,也是然並卵的）,那麼後續事件就將會收到。
MyLinearLayout: dispatchTouchEvent0 MyLinearLayout: onInterceptTouchEvent0 MyView: dispatchTouchEvent0 MyLinearLayout: dispatchTouchEvent2 MyLinearLayout: onInterceptTouchEvent2 MyView: dispatchTouchEvent2 MyLinearLayout: dispatchTouchEvent1 MyLinearLayout: onInterceptTouchEvent1 MyView: dispatchTouchEvent1
下一步開始攔截
-
onInterceptTouchEvent中Action_Move的時候返回true
MyLinearLayout: dispatchTouchEvent_ACTION_DOWN MyLinearLayout: onInterceptTouchEvent_ACTION_DOWN MyView: dispatchTouchEvent_ACTION_DOWN MyView: onTouchEvent_ACTION_DOWN MyLinearLayout: dispatchTouchEvent_ACTION_MOVE MyLinearLayout: onInterceptTouchEvent_ACTION_MOVE MyLinearLayout: 開始攔截 //注意下面MyView中收到的事件是：Cancel MyView: dispatchTouchEvent_ACTION_CANCEL MyView: onTouchEvent_ACTION_CANCEL MyLinearLayout: dispatchTouchEvent_ACTION_MOVE MyLinearLayout: onTouchEvent_ACTION_MOVE MyLinearLayout: dispatchTouchEvent_ACTION_MOVE MyLinearLayout: onTouchEvent_ACTION_MOVE MyLinearLayout: dispatchTouchEvent_ACTION_UP MyLinearLayout: onTouchEvent_ACTION_UP //對上面的log進行代碼分析 final boolean cancelChild = resetCancelNextUpFlag(target.child) || intercepted; //intercepted爲true if (dispatchTransformedTouchEvent(ev, cancelChild, target.child, target.pointerIdBits)) { handled = true;} //注意上面第二個參數，因爲攔截了，傳來是true dispatchTransformedTouchEvent final int oldAction = event.getAction(); //cancel爲true if (cancel || oldAction == MotionEvent.ACTION_CANCEL) { //在這設置了爲Cancel,所以父類攔截，子View收到的事件的Cancel, //當連續的下一次事件進入，mFirstTouchTarget爲空，又不是down事件，因此，onInterceptTouchEvent根本不會執行，直接執行父類的dispatchTouchEvent,分發給onTouchEvent event.setAction(MotionEvent.ACTION_CANCEL); if (child == null) { handled = super.dispatchTouchEvent(event); } else { //孩子收到cancel事件 handled = child.dispatchTouchEvent(event); } event.setAction(oldAction); return handled; } -
注意，一旦父類onInteceptTouchEvent就是完全進行了，不能在這個事件流中分發給子View了。
俗話說的好， 任何不配圖的分析都是耍流氓因此：
