福州正规网站建设公司报价,网站排名推广软件,个人网站开发的现状,上海到北京高铁最快几小时这篇主要是第一篇回顾之后#xff0c;补充一些上一篇没写到的两个点。 第一个的切入点是这个。【处理层叠的view#xff0c;想要执行下一层的view的点击事件】其背后的原理。
处理层叠的view#xff0c;要执行下一层的view的点击事件
我们知道#xff0c;方法是将上一层的…这篇主要是第一篇回顾之后补充一些上一篇没写到的两个点。 第一个的切入点是这个。【处理层叠的view想要执行下一层的view的点击事件】其背后的原理。
处理层叠的view要执行下一层的view的点击事件
我们知道方法是将上一层的view设置setOnTouchListener的onTouch() return false;
iv_right.setOnTouchListener { _, _ -false
}那么原理是啥其实看源码就可以了解。 首先viewGroup的 dispatchTouchEvent 在 onInterceptTouchEvent不拦截的情况下 传递Event到 view的 dispatchTouchEvent然后在 其方法体中实现原理如一下源代码
if (onFilterTouchEventForSecurity(event)) {if ((mViewFlags ENABLED_MASK) ENABLED handleScrollBarDragging(event)) {result true;}//noinspection SimplifiableIfStatementListenerInfo 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;}}//...return result;而onTouchEvent默认是false。因此最后的result就是返回了false。这个时候会回到ViewGroup层。再回过来看其 dispatchTouchEvent的这段代码
//...(此处省略部分源码)
final int childrenCount mChildrenCount;if (newTouchTarget null childrenCount ! 0) {final float x isMouseEvent ? ev.getXCursorPosition() : ev.getX(actionIndex);final float y isMouseEvent ? ev.getYCursorPosition() : ev.getY(actionIndex);// Find a child that can receive the event.// Scan children from front to back.final ArrayListView 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 (!child.canReceivePointerEvents()|| !isTransformedTouchPointInView(x, y, child, null)) {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 indexfor (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 didnt handle the event, so clear// the flag and do a normal dispatch to all children.ev.setTargetAccessibilityFocus(false);}由此可知viewgroup会在这个方法中遍历对应区域下的所有view。如果所有view都没消费掉这个Event的时候dispatchTouchEvent会继续执行接下来的代码 // 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);这这段代码中可以看到进入了if语句语句中执行了dispatchTransformedTouchEvent()方法。可以看到它的源码中它会在这个场景下回调super.dispatchTouchEvent(event);最终执行了viewGroup自身的onTouchEvent方法。 private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,View child, int desiredPointerIdBits) {final boolean handled;// Canceling motions is a special case. We dont need to perform any transformations// or filtering. The important part is the action, not the contents.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;}//...(此处省略部分源码)
}这样最终形成闭环。也就是上一篇文章所画的流程了。第一篇在这Android事件分发机制
click在整体流程中的哪个节点上
这个其实在第一篇的4.3节有提到过。但是没说得很多在这里补充一下。 这个问题的切入点我们从最常见的设置点击事件开始说起。
mTv.setOnClickListener(v - {});这里设置给了View的mOnClickListener。然后这个回调会在performClick中被调用。 public boolean performClick() {// We still need to call this method to handle the cases where performClick() was called// externally, instead of through performClickInternal()notifyAutofillManagerOnClick();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);notifyEnterOrExitForAutoFillIfNeeded(true);return result;}然后它会在onTouchEvent中被调用。具体是在MotionEvent.ACTION_UP中执行了performClickInternal()。 看部分源码如下
//...(此处省略部分源码)
if (clickable || (viewFlags TOOLTIP) TOOLTIP) {switch (action) {case MotionEvent.ACTION_UP:mPrivateFlags3 ~PFLAG3_FINGER_DOWN;if ((viewFlags TOOLTIP) TOOLTIP) {handleTooltipUp();}if (!clickable) {removeTapCallback();removeLongPressCallback();mInContextButtonPress false;mHasPerformedLongPress false;mIgnoreNextUpEvent false;break;}boolean prepressed (mPrivateFlags PFLAG_PREPRESSED) ! 0;if ((mPrivateFlags PFLAG_PRESSED) ! 0 || prepressed) {// take focus if we dont have it already and we should in// touch mode.boolean focusTaken false;if (isFocusable() isFocusableInTouchMode() !isFocused()) {focusTaken requestFocus();}if (prepressed) {// The button is being released before we actually// showed it as pressed. Make it show the pressed// state now (before scheduling the click) to ensure// the user sees it.setPressed(true, x, y);}if (!mHasPerformedLongPress !mIgnoreNextUpEvent) {// This is a tap, so remove the longpress checkremoveLongPressCallback();// Only perform take click actions if we were in the pressed stateif (!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();}if (!post(mPerformClick)) {performClickInternal();}}}//...(此处省略部分源码)
