上文已經(jīng)分析了 View 的事件分發(fā)衔蹲，View 事件分發(fā)的流程為 onTouch -> onTouchEvent -> onClick，而且一定會(huì)執(zhí)行 dispatchTouchEvent 方法
下面還是通過(guò)例子來(lái)分析
public class TouchViewGroup extends RelativeLayout {
public TouchViewGroup(Context context) {
super(context);
}
public TouchViewGroup(Context context, AttributeSet attrs) {
super(context, attrs);
}
public TouchViewGroup(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
Log.d("V10Activity", "onTouchEvent -> TouchViewGroup" + event.getAction());
return super.onTouchEvent(event);
}
@Override
public boolean dispatchTouchEvent(MotionEvent event) {
Log.d("V10Activity", "dispatchTouchEvent -> TouchViewGroup" + event.getAction());
return super.dispatchTouchEvent(event);
}
}
在 Activity 中注冊(cè)監(jiān)聽(tīng)事件
v10Binding.touchGroup.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
Log.d("V10Activity", "onTouch -> TouchGroup" + event.getAction());
return false;
}
});
v10Binding.btn1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d("V10Activity", "btn1 onClick");
}
});
v10Binding.btn2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d("V10Activity", "btn2 onClick");
}
});
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點(diǎn)擊 Button1
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點(diǎn)擊 Button2
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點(diǎn)擊空白區(qū)域
空白點(diǎn)擊.png
雖然執(zhí)行了 ViewGroup 的 dispatchTouchEvent 方法，但是并沒(méi)有執(zhí)行 onTouch 方法，所以咋們從 dispatchTouchEvent 源碼分析
ViewGroup -> dispatchTouchEvent
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
...
//當(dāng)執(zhí)行 DOWN 事件會(huì)去清除重置 Touch 狀態(tài)
if (actionMasked == MotionEvent.ACTION_DOWN) {
// Throw away all previous state when starting a new touch gesture.
// The framework may have dropped the up or cancel event for the previous gesture
// due to an app switch, ANR, or some other state change.
cancelAndClearTouchTargets(ev);
resetTouchState();
}
final boolean intercepted;
//DOWN 會(huì)進(jìn)行攔截
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
if (!disallowIntercept) {
//onInterceptTouchEvent 默認(rèn)返回 false,不攔截
intercepted = onInterceptTouchEvent(ev);
ev.setAction(action); // restore action in case it was changed
} else {
//不攔截
intercepted = false;
}
} else {
intercepted = true;
}
final boolean canceled = resetCancelNextUpFlag(this)
|| actionMasked == MotionEvent.ACTION_CANCEL;
final boolean split = (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) != 0;
//初始化新的 Touch 狀態(tài)
TouchTarget newTouchTarget = null;
boolean alreadyDispatchedToNewTouchTarget = false;
//沒(méi)有取消也沒(méi)有攔截赡磅，則分發(fā)給子View
if (!canceled && !intercepted) {
if (actionMasked == MotionEvent.ACTION_DOWN
|| (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN)
|| actionMasked == MotionEvent.ACTION_HOVER_MOVE) {
//如果 Touch 狀態(tài)為空并且子 View 個(gè)數(shù)不為 0
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();
//循環(huán)查找
for (int i = childrenCount - 1; i >= 0; i--) {
//分發(fā)事件涡驮，記錄狀態(tài)
if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {
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;
}
}
}
}
}
...
}
dispatchTransformedTouchEvent
private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,
View child, int desiredPointerIdBits) {
...
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;
...
}
ViewGroup 的 dispatchTouchEven 首先會(huì)判斷事件類型暗甥，如果為 DOWN 事件則不進(jìn)行攔截，將事件分發(fā)給子 View捉捅。如果子View 為 0 則自己處理撤防，否則通過(guò)循環(huán)便利。
所以我們修改 onInterceptTouchEvent 返回值
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
return true;
}
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點(diǎn)擊 Button1
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點(diǎn)擊 Button2
-
點(diǎn)擊空白區(qū)域
最終都被 ViewGroup 消費(fèi)了
ViewGroup 事件分發(fā)流程圖
ViewGroup 事件分發(fā)總結(jié)
- 事件分發(fā)首先會(huì)調(diào)用 ViewGroup 的 dispatchTouchEvent 方法
- 接著會(huì)判斷 onInterceptTouchEvent 的返回值
- 當(dāng) onInterceptTouchEvent 返回 false 時(shí)棒口，會(huì)分發(fā)給子View寄月，當(dāng) onInterceptTouchEvent 返回 true 時(shí)，會(huì)將事件攔截交給 ViewGroup 處理
ViewGroup 事件分發(fā)大致就介紹到這里了无牵，如果有什么寫得不對(duì)的漾肮，可以在下方評(píng)論留言，我會(huì)第一時(shí)間改正茎毁。
