編輯:關於Android編程
先來說說我遇到的問題,這次測試使用的布局文件是:
也就是說布局圖是醬紫的:
具體就是我在MyRelativeLayout中攔截了MOVE事件,在MyLinearLayout中攔截並且消費了DOWN事件,也就是說我僅僅修改了MyRelativeLayout$onInterceptTouchEvent中case條件為MOVE的部分以及MyLinearLayout$onInterceptTouchEvent中case條件為DOWN的部分和MyLinearLayout$onTouchEvent中case條件為DOWN的部分;
最後查看Logcat輸出:
06-28 09:09:25.237: I/System.out(1643): MainActivity--->dispatchTouchEvent--->ACTION_DOWN 06-28 09:09:25.237: I/System.out(1643): MyRelativeLayout--->dispatchTouchEvent--->ACTION_DOWN 06-28 09:09:25.237: I/System.out(1643): MyRelativeLayout--->onInterceptTouchEvent--->ACTION_DOWN 06-28 09:09:25.237: I/System.out(1643): MyRelativeLayout--->onInterceptTouchEvent--->ACTION_DOWN--->false 06-28 09:09:25.237: I/System.out(1643): MyLinearLayout--->dispatchTouchEvent--->ACTION_DOWN 06-28 09:09:25.237: I/System.out(1643): MyLinearLayout--->onInterceptTouchEvent--->ACTION_DOWN 06-28 09:09:25.237: I/System.out(1643): MyLinearLayout--->onInterceptTouchEvent--->ACTION_DOWN--->true 06-28 09:09:25.246: I/System.out(1643): MyLinearLayout--->onTouchEvent--->ACTION_DOWN 06-28 09:09:25.246: I/System.out(1643): MyLinearLayout--->onTouchEvent--->ACTION_DOWN--->true 06-28 09:09:25.246: I/System.out(1643): MyLinearLayout--->dispatchTouchEvent--->ACTION_DOWN--->true 06-28 09:09:25.246: I/System.out(1643): MyRelativeLayout--->dispatchTouchEvent--->ACTION_DOWN--->true 06-28 09:09:25.246: I/System.out(1643): MainActivity--->dispatchTouchEvent--->ACTION_DOWN--->true 06-28 09:09:25.326: I/System.out(1643): MainActivity--->dispatchTouchEvent--->ACTION_MOVE 06-28 09:09:25.326: I/System.out(1643): MyRelativeLayout--->dispatchTouchEvent--->ACTION_MOVE 06-28 09:09:25.326: I/System.out(1643): MyRelativeLayout--->onInterceptTouchEvent--->ACTION_MOVE 06-28 09:09:25.326: I/System.out(1643): MyRelativeLayout--->onInterceptTouchEvent--->ACTION_MOVE--->true 06-28 09:09:25.326: I/System.out(1643): MyLinearLayout--->dispatchTouchEvent--->ACTION_CANCEL 06-28 09:09:25.326: I/System.out(1643): MyLinearLayout--->dispatchTouchEvent--->ACTION_CANCEL--->false 06-28 09:09:25.326: I/System.out(1643): MyRelativeLayout--->dispatchTouchEvent--->ACTION_MOVE--->false 06-28 09:09:25.326: I/System.out(1643): MainActivity--->onTouchEvent--->ACTION_MOVE 06-28 09:09:25.326: I/System.out(1643): MainActivity--->onTouchEvent--->ACTION_MOVE--->false 06-28 09:09:25.326: I/System.out(1643): MainActivity--->dispatchTouchEvent--->ACTION_MOVE--->false 06-28 09:09:25.336: I/System.out(1643): MainActivity--->dispatchTouchEvent--->ACTION_MOVE 06-28 09:09:25.336: I/System.out(1643): MyRelativeLayout--->dispatchTouchEvent--->ACTION_MOVE 06-28 09:09:25.336: I/System.out(1643): MyRelativeLayout--->onTouchEvent--->ACTION_MOVE 06-28 09:09:25.336: I/System.out(1643): MyRelativeLayout--->onTouchEvent--->ACTION_MOVE--->false 06-28 09:09:25.336: I/System.out(1643): MyRelativeLayout--->dispatchTouchEvent--->ACTION_MOVE--->false 06-28 09:09:25.336: I/System.out(1643): MainActivity--->onTouchEvent--->ACTION_MOVE 06-28 09:09:25.336: I/System.out(1643): MainActivity--->onTouchEvent--->ACTION_MOVE--->false 06-28 09:09:25.336: I/System.out(1643): MainActivity--->dispatchTouchEvent--->ACTION_MOVE--->false 06-28 09:09:25.412: I/System.out(1643): MainActivity--->dispatchTouchEvent--->ACTION_UP 06-28 09:09:25.416: I/System.out(1643): MyRelativeLayout--->dispatchTouchEvent--->ACTION_UP 06-28 09:09:25.416: I/System.out(1643): MyRelativeLayout--->onTouchEvent--->ACTION_UP 06-28 09:09:25.416: I/System.out(1643): MyRelativeLayout--->onTouchEvent--->ACTION_UP--->false 06-28 09:09:25.416: I/System.out(1643): MyRelativeLayout--->dispatchTouchEvent--->ACTION_UP--->false 06-28 09:09:25.416: I/System.out(1643): MainActivity--->onTouchEvent--->ACTION_UP 06-28 09:09:25.416: I/System.out(1643): MainActivity--->onTouchEvent--->ACTION_UP--->false 06-28 09:09:25.416: I/System.out(1643): MainActivity--->dispatchTouchEvent--->ACTION_UP--->false
下面我們來分析下具體的輸出過程
為了便於分析,先來貼出此測試過程中用到的部分源碼:
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; }
具體分析過程:
注意:分發順序是:Activity----->ViewGroup----->View
消費順序是:View------>ViewGroup----->Activity
View中的事件方法執行流程是:dispatchTouchEvent----->onTouchEvent
ViewGroup中的事件方法執行流程是:dispatchTouchEvent----->onInterceptTouchEvent----->onTouchEvent
(1)先來看DOWN事件部分:
事件首先傳遞到MainActivity,調用它的dispatchTouchEvent分發到他的子View(MyRelativeLayout上),因為是DOWN事件,滿足ViewGroup$dispatchTouchEvent源碼的第23行if語句的第一個條件,進入if語句塊中,因為我們並沒有調用requestDisallowInterceptTouchEvent來干預事件的分發過程,所以會執行第27行的onInterceptTouchEvent方法,我們的測試中MyRelativeLayout沒有攔截DOWN事件,因而該方法默認返回值是false賦給intercepted,所以你有了Logcat第4行的輸出,接著執行第46行,滿足if語句條件,進入if語句塊中,這個裡面比較關鍵的代碼是第85行的dispatchTransformedTouchEvent方法,這個方法會遞歸的處理當前View的子View,所以你會發現Logcat第11行MyRelativeLayout的dispatchTouchEvent方法才算真正結束,這裡只需要知道第91行會調用addTouchTarget方法,該方法會在其子View的分發事件(dispatchTouchEvent)返回true的情況下執行,在它裡面會給mFirstTouchTarget賦值即可,因為MyRelativeLayout子View是MyLinearLayout,所以執行MyLinearLayout的dispatchTouchEvent方法,接著執行MyLinearLayout的onInterceptTouchEvent方法,因為MyLinearLayout攔截了DOWN事件,因而onInterceptTouchEvent返回true,那麼這時候ViewGroup$dispatchTouchEvent的第46---108行代碼將不再執行,因為此時mFirstTouchTarget還是null的,所以會執行第111行的if語句塊,調用dispatchTransformedTouchEvent方法,傳入的第三個參數是null,查看ViewGroup$dispatchTransformedTouchEvent源碼的第11行,發現他會執行super的dispatchTouchEvent方法,因為我們沒有為MyLinearLayout設置onTouch監聽事件,所以他直接執行了onTouchEvent方法,並且我們消費了這個DOWN事件,所以有了Logcat第9行的輸出,接下來就是遞歸返回過程了,即Logcat第10--12行的輸出部分;
(2)接下來分析第一次MOVE事件
和上面一樣,事件首先到了MainActivity,調用他的dispatchTouchEvent方法進行分發,接著事件分發到了MyRelativeLayout上面,調用他的dispatchTouchEvent方法,因為第一次DOWN事件中,我們已經將mFirstTouchTarget的值設置為非null,所以ViewGroup$dispatchTouchEvent方法走到第23行的時候仍然滿足if判斷條件,執行第27行的onInterceptTouchEvent方法,所以有了第15行的Logcat輸出,因為我們在MyRelativeLayout中攔截了MOVE事件,所以intercepted的值將會被賦值為true,因而ViewGroup$dispatchTouchEvent的第46--108行的代碼將不會執行,到了第111行判斷mFirstTouchTarget不為null,執行else語句部分,這裡比較關鍵的在於第125行,因為此時的intercepted值為true,所以cancelChild值將為true,在執行第127行dispatchTransformedTouchEvent的時候將cancelChild值傳入,查看ViewGroup$dispatchTransformedTouchEvent的源碼第9行,你會發現他執行了ACTION_CANCEL,所以出現了我們Logcat輸出的第17/18行,因而第127行的if條件內容將為false,所以handled的值此時仍然是false,因為cancelChild值是true,所以執行第131行,並且此時的predecessor等於null,因而修改mFirstTouchTarget的值為next,這裡就比較重要了,此處的next是null,為什麼呢?因為之前mFirstTouchTarget的值是MyLinearLayout,雖然MyLinearLayout有子View(MyButton),但是MyLinearLayout把DOWN時間消費了,所以MyButton根本就沒有加入到事件處理的鏈表中,所以對mFirstTouchTarget的值進行了修改,ViewGroup$dispatchTouchEvent的第148--161行不再會修改handled的值,那麼我們可以認為MyRelativeLayout的dispatchTouchEvent方法執行結束,因為此時事件還沒有被消費,那麼只能由MainActivity來進行處理了,所以有了Logcat第20--22行的輸出;
(3)接下來分析第二次以後的MOVE事件
同樣事件首先由MainActivity的dispatchTouchEvent分發到MyRelativeLayout上,執行他的dispatchTouchEvent方法,這時候判斷ViewGroup$dispatchTouchEvent第23行的if語句部分,發現部門組條件,那麼會執行第35行的else語句部分,設置intercepted的值為true,同樣的不會執行第46--108行部分,在判斷第111行的mFirstTouchTarget是否為null時,滿足條件,執行dispatchTransformedTouchEvent方法,傳入的第3個參數是null,那麼會執行super的dispatchTouchEvent方法,這屬於View的事件分發過程,同樣我們沒有為MyRelativeLayout設置onTouch方法,所以他會直接執行onTouchEvent方法,所以有了Logcat第25行的輸出,接下來在onTouchEvent執行結束之後返回false,因為我們沒有在MyRelativeLayout中消費MOVE事件,因為該事件沒有處理完,因而會回傳給MainActivity來進行處理;
(4)接下來就是UP事件了:
UP事件的分析和第二次以後的MOVE事件過程一致,就不再贅述了;
從上面的分析中,我們可以得出結論:
某一個View一旦決定攔截,那麼這個事件序列以後的部分只能由他來處理,前提條件是以後的事件是可以到達該View的,就像上面的例子,DOWN事件是由MyLinearLayout來攔截消費的,但是MOVE事件卻不是他處理的,原因在於MyRelativeLayout對MOVE事件進行了攔截,事件根本就不會到達MyLinearLayout;
有時候用到Android模擬器來模擬SD卡相關操作,在Eclipse中可以直接查看SD卡目錄; 首先,新建模擬器的時候要創建SD卡,存儲的大小根據需要創建; 啟動模擬
最近的項目中給ListView 加入了一個Header View之後,發現Header View的下方也有了分割線,很難看,UI要求將Header View的分割器去掉
作者 : 韓曙亮轉載請著名出處 : http://blog.csdn.net/shulianghan/article/details/38064191本博客代碼地址 :
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