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android-----事件分发机制测试系列

来源:程序员人生   发布时间:2016-07-18 08:29:51 阅读次数:1614次

        先来讲说我遇到的问题,这次测试使用的布局文件是:

<com.hzw.eventtest.MyRelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" > <com.hzw.eventtest.MyLinearLayout android:layout_width="match_parent" android:layout_height="match_parent"> <com.hzw.eventtest.MyButton android:id="@+id/mybutton" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="我的按钮" /> </com.hzw.eventtest.MyLinearLayout> </com.hzw.eventtest.MyRelativeLayout>

        也就是说布局图是酱紫的:

                                                      

        具体就是我在MyRelativeLayout中拦截了MOVE事件,在MyLinearLayout中拦截并且消费了DOWN事件,也就是说我仅仅修改了MyRelativeLayout$onInterceptTouchEvent中case条件为MOVE的部份和MyLinearLayout$onInterceptTouchEvent中case条件为DOWN的部份和MyLinearLayout$onTouchEvent中case条件为DOWN的部份;

        具体测试代码:点击下载

        最后查看Logcat输出:

06⑵8 09:09:25.237: I/System.out(1643): MainActivity--->dispatchTouchEvent--->ACTION_DOWN 06⑵8 09:09:25.237: I/System.out(1643): MyRelativeLayout--->dispatchTouchEvent--->ACTION_DOWN 06⑵8 09:09:25.237: I/System.out(1643): MyRelativeLayout--->onInterceptTouchEvent--->ACTION_DOWN 06⑵8 09:09:25.237: I/System.out(1643): MyRelativeLayout--->onInterceptTouchEvent--->ACTION_DOWN--->false 06⑵8 09:09:25.237: I/System.out(1643): MyLinearLayout--->dispatchTouchEvent--->ACTION_DOWN 06⑵8 09:09:25.237: I/System.out(1643): MyLinearLayout--->onInterceptTouchEvent--->ACTION_DOWN 06⑵8 09:09:25.237: I/System.out(1643): MyLinearLayout--->onInterceptTouchEvent--->ACTION_DOWN--->true 06⑵8 09:09:25.246: I/System.out(1643): MyLinearLayout--->onTouchEvent--->ACTION_DOWN 06⑵8 09:09:25.246: I/System.out(1643): MyLinearLayout--->onTouchEvent--->ACTION_DOWN--->true 06⑵8 09:09:25.246: I/System.out(1643): MyLinearLayout--->dispatchTouchEvent--->ACTION_DOWN--->true 06⑵8 09:09:25.246: I/System.out(1643): MyRelativeLayout--->dispatchTouchEvent--->ACTION_DOWN--->true 06⑵8 09:09:25.246: I/System.out(1643): MainActivity--->dispatchTouchEvent--->ACTION_DOWN--->true 06⑵8 09:09:25.326: I/System.out(1643): MainActivity--->dispatchTouchEvent--->ACTION_MOVE 06⑵8 09:09:25.326: I/System.out(1643): MyRelativeLayout--->dispatchTouchEvent--->ACTION_MOVE 06⑵8 09:09:25.326: I/System.out(1643): MyRelativeLayout--->onInterceptTouchEvent--->ACTION_MOVE 06⑵8 09:09:25.326: I/System.out(1643): MyRelativeLayout--->onInterceptTouchEvent--->ACTION_MOVE--->true 06⑵8 09:09:25.326: I/System.out(1643): MyLinearLayout--->dispatchTouchEvent--->ACTION_CANCEL 06⑵8 09:09:25.326: I/System.out(1643): MyLinearLayout--->dispatchTouchEvent--->ACTION_CANCEL--->false 06⑵8 09:09:25.326: I/System.out(1643): MyRelativeLayout--->dispatchTouchEvent--->ACTION_MOVE--->false 06⑵8 09:09:25.326: I/System.out(1643): MainActivity--->onTouchEvent--->ACTION_MOVE 06⑵8 09:09:25.326: I/System.out(1643): MainActivity--->onTouchEvent--->ACTION_MOVE--->false 06⑵8 09:09:25.326: I/System.out(1643): MainActivity--->dispatchTouchEvent--->ACTION_MOVE--->false 06⑵8 09:09:25.336: I/System.out(1643): MainActivity--->dispatchTouchEvent--->ACTION_MOVE 06⑵8 09:09:25.336: I/System.out(1643): MyRelativeLayout--->dispatchTouchEvent--->ACTION_MOVE 06⑵8 09:09:25.336: I/System.out(1643): MyRelativeLayout--->onTouchEvent--->ACTION_MOVE 06⑵8 09:09:25.336: I/System.out(1643): MyRelativeLayout--->onTouchEvent--->ACTION_MOVE--->false 06⑵8 09:09:25.336: I/System.out(1643): MyRelativeLayout--->dispatchTouchEvent--->ACTION_MOVE--->false 06⑵8 09:09:25.336: I/System.out(1643): MainActivity--->onTouchEvent--->ACTION_MOVE 06⑵8 09:09:25.336: I/System.out(1643): MainActivity--->onTouchEvent--->ACTION_MOVE--->false 06⑵8 09:09:25.336: I/System.out(1643): MainActivity--->dispatchTouchEvent--->ACTION_MOVE--->false 06⑵8 09:09:25.412: I/System.out(1643): MainActivity--->dispatchTouchEvent--->ACTION_UP 06⑵8 09:09:25.416: I/System.out(1643): MyRelativeLayout--->dispatchTouchEvent--->ACTION_UP 06⑵8 09:09:25.416: I/System.out(1643): MyRelativeLayout--->onTouchEvent--->ACTION_UP 06⑵8 09:09:25.416: I/System.out(1643): MyRelativeLayout--->onTouchEvent--->ACTION_UP--->false 06⑵8 09:09:25.416: I/System.out(1643): MyRelativeLayout--->dispatchTouchEvent--->ACTION_UP--->false 06⑵8 09:09:25.416: I/System.out(1643): MainActivity--->onTouchEvent--->ACTION_UP 06⑵8 09:09:25.416: I/System.out(1643): MainActivity--->onTouchEvent--->ACTION_UP--->false 06⑵8 09:09:25.416: I/System.out(1643): MainActivity--->dispatchTouchEvent--->ACTION_UP--->false

        下面我们来分析下具体的输出进程

        为了便于分析,先来贴出此测试进程中用到的部份源码:

        ViewGroup$dispatchTouchEvent

@Override public boolean dispatchTouchEvent(MotionEvent ev) { if (mInputEventConsistencyVerifier != null) { mInputEventConsistencyVerifier.onTouchEvent(ev, 1); } 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) { // 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(); } // Check for interception. final boolean intercepted; if (actionMasked == MotionEvent.ACTION_DOWN || mFirstTouchTarget != null) { final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0; if (!disallowIntercept) { intercepted = onInterceptTouchEvent(ev); ev.setAction(action); // restore action in case it was changed } else { 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; } // Check for cancelation. final boolean canceled = resetCancelNextUpFlag(this) || actionMasked == MotionEvent.ACTION_CANCEL; // Update list of touch targets for pointer down, if needed. final boolean split = (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) != 0; TouchTarget newTouchTarget = null; boolean alreadyDispatchedToNewTouchTarget = false; if (!canceled && !intercepted) { 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 View[] children = mChildren; final boolean customOrder = isChildrenDrawingOrderEnabled(); for (int i = childrenCount - 1; i >= 0; i--) { final int childIndex = customOrder ? getChildDrawingOrder(childrenCount, i) : i; final View child = children[childIndex]; if (!canViewReceivePointerEvents(child) || !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(); mLastTouchDownIndex = childIndex; mLastTouchDownX = ev.getX(); mLastTouchDownY = ev.getY(); newTouchTarget = addTouchTarget(child, idBitsToAssign); alreadyDispatchedToNewTouchTarget = true; break; } } } 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; }
        ViewGroup$dispatchTransformedTouchEvent

private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel, View child, int desiredPointerIdBits) { final boolean handled; // Canceling motions is a special case. We don't 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; } // Calculate the number of pointers to deliver. final int oldPointerIdBits = event.getPointerIdBits(); final int newPointerIdBits = oldPointerIdBits & desiredPointerIdBits; // If for some reason we ended up in an inconsistent state where it looks like we // might produce a motion event with no pointers in it, then drop the event. if (newPointerIdBits == 0) { return false; } // If the number of pointers is the same and we don't need to perform any fancy // irreversible transformations, then we can reuse the motion event for this // dispatch as long as we are careful to revert any changes we make. // Otherwise we need to make a copy. 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); } // 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; }

        具体分析进程:

        注意:分发顺序是:Activity----->ViewGroup----->View

                    消费顺序是:View------>ViewGroup----->Activity

                    View中的事件方法履行流程是:dispatchTouchEvent----->onTouchEvent

                    ViewGroup中的事件方法履行流程是:dispatchTouchEvent----->onInterceptTouchEvent----->onTouchEvent

        (1)先来看DOWN事件部份:

            事件首先传递到MainActivity,调用它的dispatchTouchEvent分发到他的子View(MyRelativeLayout上),由于是DOWN事件,满足ViewGroup$dispatchTouchEvent源码的第23行if语句的第1个条件,进入if语句块中,由于我们并没有调用requestDisallowInterceptTouchEvent来干预事件的分发进程,所以会履行第27行的onInterceptTouchEvent方法,我们的测试中MyRelativeLayout没有拦截DOWN事件,因此该方法默许返回值是false赋给intercepted,所以你有了Logcat第4行的输出,接着履行第46行,满足if语句条件,进入if语句块中,这个里面比较关键的代码是第85行的dispatchTransformedTouchEvent方法,这个方法会递归的处应当前View的子View,所以你会发现Logcat第11行MyRelativeLayoutdispatchTouchEvent方法才算真正结束,这里只需要知道第91行会调用addTouchTarget方法,该方法会在其子View的分发事件(dispatchTouchEvent)返回true的情况下履行,在它里面会给mFirstTouchTarget赋值便可,由于MyRelativeLayout子View是MyLinearLayout,所以履行MyLinearLayoutdispatchTouchEvent方法,接着履行MyLinearLayoutonInterceptTouchEvent方法,由于MyLinearLayout拦截了DOWN事件,因此onInterceptTouchEvent返回true,那末这时候候ViewGroup$dispatchTouchEvent的第46--⑴08行代码将不再履行,由于此时mFirstTouchTarget还是null的,所以会履行第111行的if语句块,调用dispatchTransformedTouchEvent方法,传入的第3个参数是null,查看ViewGroup$dispatchTransformedTouchEvent源码的第11行,发现他会履行super的dispatchTouchEvent方法,由于我们没有为MyLinearLayout设置onTouch监听事件,所以他直接履行了onTouchEvent方法,并且我们消费了这个DOWN事件,所以有了Logcat第9行的输出,接下来就是递归返回进程了,即Logcat第10-⑴2行的输出部份;

        (2)接下来分析第1次MOVE事件

            和上面1样,事件首先到了MainActivity,调用他的dispatchTouchEvent方法进行分发,接着事件分发到了MyRelativeLayout上面,调用他的dispatchTouchEvent方法,由于第1次DOWN事件中,我们已将mFirstTouchTarget的值设置为非null,所以ViewGroup$dispatchTouchEvent方法走到第23行的时候依然满足if判断条件,履行第27行的onInterceptTouchEvent方法,所以有了第15行的Logcat输出,由于我们在MyRelativeLayout中拦截了MOVE事件,所以intercepted的值将会被赋值为true,因此ViewGroup$dispatchTouchEvent的第46-⑴08行的代码将不会履行,到了第111行判断mFirstTouchTarget不为null,履行else语句部份,这里比较关键的在于第125行,由于此时的intercepted值为true,所以cancelChild值将为true,在履行第127行dispatchTransformedTouchEvent的时候将cancelChild值传入,查看ViewGroup$dispatchTransformedTouchEvent的源码第9行,你会发现他履行了ACTION_CANCEL,所以出现了我们Logcat输出的第17/18行,因此第127行的if条件内容将为false,所以handled的值此时依然是false,由于cancelChild值是true,所以履行第131行,并且此时的predecessor等于null,因此修改mFirstTouchTarget的值为next,这里就比较重要了,此处的next是null,为何呢?由于之前mFirstTouchTarget的值是MyLinearLayout,虽然MyLinearLayout有子View(MyButton),但是MyLinearLayout把DOWN时间消费了,所以MyButton根本就没有加入到事件处理的链表中,所以对mFirstTouchTarget的值进行了修改,ViewGroup$dispatchTouchEvent的第148-⑴61行不再会修改handled的值,那末我们可以认为MyRelativeLayoutdispatchTouchEvent方法履行结束,由于此时事件还没有被消费,那末只能由MainActivity来进行处理了,所以有了Logcat第20-⑵2行的输出;

        (3)接下来分析第2次以后的MOVE事件

           一样事件首先由MainActivitydispatchTouchEvent分发到MyRelativeLayout上,履行他的dispatchTouchEvent方法,这时候候判断ViewGroup$dispatchTouchEvent第23行的if语句部份,发现部门组条件,那末会履行第35行的else语句部份,设置intercepted的值为true,一样的不会履行第46-⑴08行部份,在判断第111行的mFirstTouchTarget是不是为null时,满足条件,履行dispatchTransformedTouchEvent方法,传入的第3个参数是null,那末会履行super的dispatchTouchEvent方法,这属于View的事件分发进程,一样我们没有为MyRelativeLayout设置onTouch方法,所以他会直接履行onTouchEvent方法,所以有了Logcat第25行的输出,接下来在onTouchEvent履行结束以后返回false,由于我们没有在MyRelativeLayout中消费MOVE事件,由于该事件没有处理完,因此会回传给MainActivity来进行处理;

        (4)接下来就是UP事件了:

           UP事件的分析和第2次以后的MOVE事件进程1致,就不再赘述了;

        从上面的分析中,我们可以得出结论:

        某1个View1旦决定拦截,那末这个事件序列以后的部份只能由他来处理,条件条件是以后的事件是可以到达该View的,就像上面的例子,DOWN事件是由MyLinearLayout来拦截消费的,但是MOVE事件却不是他处理的,缘由在于MyRelativeLayout对MOVE事件进行了拦截,事件根本就不会到达MyLinearLayout;





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