用戶觸摸屏幕后,會生成touch事件,之后應用可以在Looper中獲得當前應用需要處理的touch事件,接下來交給ViewRootImpl去處理,ViewRootImpl確定該事件是touch事件后,傳遞給當前activity的phoneWindow里的DecorView的dispatchTouchEvent方法
本文主要回答以下問題: 1. dispatchTouchEvent過程,怎么找到目標View來處理事件的? 2. onTouch超出View的范圍時,會發生什么? 3. View的onClick方法能否和onTouch方法共用? 4. View是按照什么順序獲得touch事件的?如果有View不處理時,又如何?
如果已經知道具體答案的童鞋,那么本篇文章就可以跳過了
先看decorView的
@Override public boolean dispatchTouchEvent(MotionEvent ev) { final Callback cb = getCallback();//cb即為Activity,也就是下面的代碼會調用Activity的dispatchTouchEvent return cb != null && !isDestroyed() && mFeatureId < 0 ? cb.dispatchTouchEvent(ev) : super.dispatchTouchEvent(ev); }解釋:decorView的getCallBack()為何為Activity,原因是Actyvity的attach方法中調用了以下兩行代碼,attach則會在Activity創建過程中被調用:
mWindow = new PhoneWindow(this); mWindow.setCallback(this);Activity的dispatchTouchEvent方法:
public boolean dispatchTouchEvent(MotionEvent ev) { if (ev.getAction() == MotionEvent.ACTION_DOWN) { onUserInteraction();//默認空方法,可重寫來查看事件 } if (getWindow().superDispatchTouchEvent(ev)) {//調用PhoneWindow的dispatchTouchEvent方法 return true; } //如果所有View都不處理touch事件,那么調用Activity的onTouchEvent return onTouchEvent(ev); }PhoneWindow的dispatchTouchEvent方法實際是ViewGroup的dispatchTouchEvent方法,源碼及解釋:
@Override public boolean dispatchTouchEvent(MotionEvent ev) { if (mInputEventConsistencyVerifier != null) {//檢查事件是否一致 mInputEventConsistencyVerifier.onTouchEvent(ev, 1); } if (ev.isTargetaccessibilityFocus() && isAccessibilityFocusedViewOrHost()) { ev.setTargetAccessibilityFocus(false); } boolean handled = false; if (onFilterTouchEventForSecurity(ev)) {//如果View被遮擋,返回false,不繼續分發(遮擋可能的方式:) final int action = ev.getAction(); final int actionMasked = action & MotionEvent.ACTION_MASK; if (actionMasked == MotionEvent.ACTION_DOWN) { //當開始一個ACTION_DOWN時,清除原先的狀態,因為當遇到ANR,切換APP等變化時,事件可能被丟棄或取消 cancelAndClearTouchTargets(ev); resetTouchState(); } final boolean intercepted; if (actionMasked == MotionEvent.ACTION_DOWN || mFirstTouchTarget != null) { final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0; if (!disallowIntercept) { intercepted = onInterceptTouchEvent(ev);//先看自己是否攔截該事件 ev.setAction(action); // restore action in case it was changed } else { intercepted = false; } } else { //事件不是touch_down事件(之前已經處理touch_down事件,現在還有其他事件,說明之前進行了攔截和處理) 或者 沒有處理這個事件的view(包含在mFirstTouchTarget中),那么繼續攔截事件 intercepted = true; } //如果被打斷了,或已經有View處理這個事件了,就將這個事件作為普通事件處理 if (intercepted || mFirstTouchTarget != null) { ev.setTargetAccessibilityFocus(false); } // 檢查是否取消事件 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) {//不是取消事件 并且當前view沒攔截 View childWithAccessibilityFocus = ev.isTargetAccessibilityFocus() ? findChildWithAccessibilityFocus() : null; 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 ArrayList<View> PReorderedList = buildOrderedChildList();//按照Z向量值由小到大 final boolean customOrder = preorderedList == null && isChildrenDrawingOrderEnabled(); final View[] children = mChildren; for (int i = childrenCount - 1; i >= 0; i--) {//這里是倒序 //所以以下基本上是先看獲得焦點的view(被點擊的view),如果被點擊的view,不處理,那么處理child的順序 : Z值大 -> 小 (android5.0后) 或 view重疊順序上層 -> 下層 final int childIndex = customOrder ? getChildDrawingOrder(childrenCount, i) : i; final View child = (preorderedList == null) ? children[childIndex] : preorderedList.get(childIndex); //優先讓焦點View處理這個事件 if (childWithAccessibilityFocus != null) { if (childWithAccessibilityFocus != child) { continue; } childWithAccessibilityFocus = null; i = childrenCount - 1; } //canViewReceivePointerEvents判斷view的狀態是可以接受點擊事件的 //isTransformedTouchPointInView判斷點擊事件在View的范圍內 if (!canViewReceivePointerEvents(child) || !isTransformedTouchPointInView(x, y, child, null)) { ev.setTargetAccessibilityFocus(false); continue; } newTouchTarget = getTouchTarget(child); if (newTouchTarget != null) {//已經處理過這個touch事件了,避免重復操作 newTouchTarget.pointerIdBits |= idBitsToAssign; break; } resetCancelNextUpFlag(child); if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) { //這個方法會對Event進行一些轉換,再調用child.dispatchTouchEvent方法,如果希望處理 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; } // 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(); } if (newTouchTarget == null && mFirstTouchTarget != null) { // 沒有找到View去處理這個event // 把指針交給最久添加的target newTouchTarget = mFirstTouchTarget; while (newTouchTarget.next != null) { newTouchTarget = newTouchTarget.next; } newTouchTarget.pointerIdBits |= idBitsToAssign; } } } // Dispatch to touch targets. if (mFirstTouchTarget == null) { // child沒有在點擊范圍時,或者都沒處理時,讓該View自己來處理 handled = dispatchTransformedTouchEvent(ev, canceled, null, TouchTarget.ALL_POINTER_IDS); } else { // 分發event給目標view,除了之前那些分發過的view 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; } } // 做一些重置操作 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) {//事件未處理時,作一些忽略操作 mInputEventConsistencyVerifier.onUnhandledEvent(ev, 1); } return handled; }該方法如果child不為null,就要把Event進行一些轉換,轉成適合child處理的Event,在讓child.dispatchTouchEvent,否則交給父類super.dispatchTouchEvent處理
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; }public boolean onTouchEvent(MotionEvent event) { final float x = event.getX(); final float y = event.getY(); final int viewFlags = mViewFlags; final int action = event.getAction(); if ((viewFlags & ENABLED_MASK) == DISABLED) { if (action == MotionEvent.ACTION_UP && (mPrivateFlags & PFLAG_PRESSED) != 0) { setPressed(false); } //一個disable的view但是是clickable時,也是可以接收事件的,只是不會做出xiang'ying響應 return (((viewFlags & CLICKABLE) == CLICKABLE || (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) || (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE); } if (mTouchDelegate != null) { if (mTouchDelegate.onTouchEvent(event)) { return true; } } if (((viewFlags & CLICKABLE) == CLICKABLE || (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) || (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE) {//如果有Clickable,longClickable、ContextClickable后續直接返回true switch (action) { case MotionEvent.ACTION_UP: boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != 0; if ((mPrivateFlags & PFLAG_PRESSED) != 0 || prepressed) { // take focus if we don't have it already and we should in // touch mode. boolean focusTaken = false; if (isFocusable() && isFocusableInTouchMode() && !isFocused()) { focusTaken = requestFocus(); } if (prepressed) { // 調用setPressed方法,該方法可重寫 setPressed(true, x, y); } if (!mHasperformedLongPress && !mIgnoreNextUpEvent) { // This is a tap, so remove the longpress check removeLongPressCallback(); // 只有在點擊狀態是調用onClick方法 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(); } if (!post(mPerformClick)) { performClick(); } } } if (mUnsetPressedState == null) { mUnsetPressedState = new UnsetPressedState(); } if (prepressed) { postDelayed(mUnsetPressedState, ViewConfiguration.getPressedStateDuration()); } else if (!post(mUnsetPressedState)) { // If the post failed, unpress right now mUnsetPressedState.run(); } removeTapCallback(); } mIgnoreNextUpEvent = false; break; case MotionEvent.ACTION_DOWN: mHasPerformedLongPress = false; if (performButtonActionOnTouchDown(event)) { break; } // 查看是否在可scroll的容器里 boolean isInScrollingContainer = isInScrollingContainer(); if (isInScrollingContainer) {//如果在可scroll的容器里時,延遲事件分發,以確定是scroll事件,還是其他事件 mPrivateFlags |= PFLAG_PREPRESSED; if (mPendingCheckForTap == null) { mPendingCheckForTap = new CheckForTap(); } mPendingCheckForTap.x = event.getX(); mPendingCheckForTap.y = event.getY(); postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout()); } else { setPressed(true, x, y); checkForLongClick(0); } break; case MotionEvent.ACTION_CANCEL: setPressed(false); removeTapCallback(); removeLongPressCallback(); mInContextButtonPress = false; mHasPerformedLongPress = false; mIgnoreNextUpEvent = false; break; case MotionEvent.ACTION_MOVE: drawableHotspotChanged(x, y); // Be lenient about moving outside of buttons if (!pointInView(x, y, mTouchSlop)) {//如果移動到View外面,則不為點擊狀態 // Outside button removeTapCallback(); if ((mPrivateFlags & PFLAG_PRESSED) != 0) { // Remove any future long press/tap checks removeLongPressCallback(); setPressed(false); } } break; } return true; } return false; }View是按照什么順序獲得touch事件的?如果有View不處理時,又如何?
本View的onInterceptTouchEvent()方法 > 容器中獲得焦點的View,一般就是被點擊的View > 覆蓋在上層的View/Z軸值更大的View > 覆蓋在下層的View/Z軸值更小的View > 本View的super.dispatchTouchEvent 如果有View不處理時,按照以上順序不斷傳遞,直到有View處理
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