二、当前遍历的子组件的事件分发
首先提取当前的子组件 , 第一次执行 getTouchTarget 代码时 , 是没有 mFirstTouchTarget 的 , 此时第一次返回 null ;
newTouchTarget = getTouchTarget(child);getTouchTarget 方法 , 判断 mFirstTouchTarget 中的 child 字段 , 是否是当前遍历的 子组件 View ;
如果是 , 则返回该 TouchTarget ;
如果不是 , 则返回空 ;
此时默认返回 null ;
调用 dispatchTransformedTouchEvent 正式开始分发触摸事件 , 返回值只有两种情况 ,
① 情况一 : 子控件触摸事件返回 true
② 情况二 : 子控件触摸事件返回 false
dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)dispatchTransformedTouchEvent 方法 , 是正式分发触摸事件的方法 , 注意参数中传入了当前正在被遍历的 child 子组件 ;
首先处理取消状态 , 暂时不用分析 ;
// 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. // 处理取消状态 , 暂时不分析 ; 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; }
如果被遍历的子组件为空 , 则调用父类的分发方法 , handled = super.dispatchTouchEvent(event); , 该分支很少执行 ;
如果被遍历的子组件不为空 , 则调用子组件的分发方法 , handled = child.dispatchTouchEvent(event); , 子组件分发触摸事件 , 此处调用的是 View 组件的 dispatchTouchEvent 方法 ;
// 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) { // 被遍历的 child 子组件为空 // 调用父类的分发方法 handled = super.dispatchTouchEvent(event); } else { // 被遍历的 child 子组件不为空 final float offsetX = mScrollX - child.mLeft; final float offsetY = mScrollY - child.mTop; event.offsetLocation(offsetX, offsetY); // 子组件分发触摸事件 // 此处调用的是 View 组件的 dispatchTouchEvent 方法 ; handled = child.dispatchTouchEvent(event); event.offsetLocation(-offsetX, -offsetY); } return handled; } transformedEvent = MotionEvent.obtain(event); } else { transformedEvent = event.split(newPointerIdBits); }
ViewGroup | dispatchTouchEvent | dispatchTransformedTouchEvent 方法相关源码 :
@UiThread public abstract class ViewGroup extends View implements ViewParent, ViewManager { @Override public boolean dispatchTouchEvent(MotionEvent ev) { ... // 提取当前的子组件 // 第一次执行 getTouchTarget 代码时 , 是没有 mFirstTouchTarget 的 // 此时第一次返回 null newTouchTarget = getTouchTarget(child); // 该分支操作第一次不执行 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); // 正式开始分发触摸事件 // 处理以下两种情况 : // ① 情况一 : 子控件触摸事件返回 true // ② 情况二 : 子控件触摸事件返回 false if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) { ... } /** * Gets the touch target for specified child view. * Returns null if not found. * */ private TouchTarget getTouchTarget(@NonNull View child) { // 判断 mFirstTouchTarget 中的 child 字段 , 是否是当前遍历的 子组件 View // 如果是 , 则返回该 TouchTarget // 如果不是 , 则返回空 for (TouchTarget target = mFirstTouchTarget; target != null; target = target.next) { if (target.child == child) { return target; } } return null; } /** * Transforms a motion event into the coordinate space of a particular child view, * filters out irrelevant pointer ids, and overrides its action if necessary. * If child is null, assumes the MotionEvent will be sent to this ViewGroup instead. * 该方法是正式分发触摸事件的方法 * 注意参数中传入了当前正在被遍历的 child 子组件 */ 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. // 处理取消状态 , 暂时不分析 ; 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) { // 被遍历的 child 子组件为空 // 调用父类的分发方法 handled = super.dispatchTouchEvent(event); } else { // 被遍历的 child 子组件不为空 final float offsetX = mScrollX - child.mLeft; final float offsetY = mScrollY - child.mTop; event.offsetLocation(offsetX, offsetY); // 子组件分发触摸事件 // 此处调用的是 View 组件的 dispatchTouchEvent 方法 ; 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; } }
源码路径 : /frameworks/base/core/java/android/view/ViewGroup.java
三、ViewGroup 事件分发相关源码
ViewGroup 事件分发相关源码 : 下面的代码中 , 逐行注释分析了 ViewGroup 的 dispatchTouchEvent 事件分发操作 ;
@UiThread public abstract class ViewGroup extends View implements ViewParent, ViewManager { // First touch target in the linked list of touch targets. private TouchTarget mFirstTouchTarget; @Override public boolean dispatchTouchEvent(MotionEvent ev) { // 辅助功能 , 残疾人相关辅助 , 跨进程调用 无障碍 功能 if (mInputEventConsistencyVerifier != null) { mInputEventConsistencyVerifier.onTouchEvent(ev, 1); } // If the event targets the accessibility focused view and this is it, start // normal event dispatch. Maybe a descendant is what will handle the click. // 判断产生事件的目标组件是可访问性的 , 那么按照普通的事件分发进行处理 ; // 可能由其子类处理点击事件 ; // 判断当前是否正在使用 无障碍 相关功能产生事件 if (ev.isTargetAccessibilityFocus() && isAccessibilityFocusedViewOrHost()) { ev.setTargetAccessibilityFocus(false); } // 是否按下操作 , 最终的对外返回结果 , 该方法的最终返回值 boolean handled = false; if (onFilterTouchEventForSecurity(ev)) { final int action = ev.getAction(); final int actionMasked = action & MotionEvent.ACTION_MASK; // Handle an initial down. // 判断是否是第一次按下 , 如果是第一次按下 , 则执行下面的业务逻辑 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); // 如果是第一次按下 , 那么重置触摸状态 resetTouchState(); } // Check for interception. // 判定是否拦截 // 用于多点触控按下操作的判定 final boolean intercepted; if (actionMasked == MotionEvent.ACTION_DOWN || mFirstTouchTarget != null) { // 判断是否需要拦截 , 可以使用 requestDisallowInterceptTouchEvent 方法进行设置 final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0; if (!disallowIntercept) { // 进行事件拦截 // 该 onInterceptTouchEvent 方法只返回是否进行事件拦截 , 返回一个布尔值 , 没有进行具体的事件拦截 // 是否进行拦截 , 赋值给了 intercepted 局部变量 // 该值决定是否进行拦截 intercepted = onInterceptTouchEvent(ev); ev.setAction(action); // restore action in case it was changed } else { // 不进行事件拦截 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; } // If intercepted, start normal event dispatch. Also if there is already // a view that is handling the gesture, do normal event dispatch. if (intercepted || mFirstTouchTarget != null) { ev.setTargetAccessibilityFocus(false); } // Check for cancelation. // 检查是否取消操作 , 手指是否移除了组件便捷 ; // 一般情况默认该值是 false ; 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; // 注意此处 newTouchTarget 为空 TouchTarget newTouchTarget = null; boolean alreadyDispatchedToNewTouchTarget = false; // 此处判定 , 是否拦截 // 假定不取消 , 也不拦截 // canceled 和 intercepted 二者都是 false , 才不能拦截 ; if (!canceled && !intercepted) { // If the event is targeting accessibility focus we give it to the // view that has accessibility focus and if it does not handle it // we clear the flag and dispatch the event to all children as usual. // We are looking up the accessibility focused host to avoid keeping // state since these events are very rare. // 无障碍 辅助功能 View childWithAccessibilityFocus = ev.isTargetAccessibilityFocus() ? findChildWithAccessibilityFocus() : null; // 判断是否是按下操作 if (actionMasked == MotionEvent.ACTION_DOWN || (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN) || actionMasked == MotionEvent.ACTION_HOVER_MOVE) { // 获取触摸索引值 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); // 计算 ViewGroup 父容器下面有多少个子 View 组件 ; final int childrenCount = mChildrenCount; // TouchTarget newTouchTarget = null; 在上面声明为空 , 此处肯定为 null ; // childrenCount 子组件个数不为 0 // 如果子组件个数为 0 , 则不走下一段代码 , 如果子组件个数大于 0 , 则执行下一段代码 ; // 说明下面的代码块中处理的是 ViewGroup 中子组件的事件分发功能 ; if (newTouchTarget == null && childrenCount != 0) { // 获取单个手指的 x,y 坐标 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. // 子组件排序 , 按照 Z 轴排列的层级 , 从上到下进行排序 , // 控件会相互重叠 , Z 轴的排列次序上 , // 顶层的组件优先获取到触摸事件 final ArrayList<View> preorderedList = buildTouchDispatchChildList(); final boolean customOrder = preorderedList == null && isChildrenDrawingOrderEnabled(); final View[] children = mChildren; // 倒序遍历 按照 Z 轴的上下顺序 , 排列好的组件 // 先遍历的 Z 轴方向上 , 放在最上面的组件 , 也就是顶层组件 for (int i = childrenCount - 1; i >= 0; i--) { // 获取索引 final int childIndex = getAndVerifyPreorderedIndex( childrenCount, i, customOrder); // 获取索引对应组件 final View child = getAndVerifyPreorderedView( preorderedList, children, childIndex); // If there is a view that has accessibility focus we want it // to get the event first and if not handled we will perform a // normal dispatch. We may do a double iteration but this is // safer given the timeframe. // 无障碍 辅助功能 if (childWithAccessibilityFocus != null) { if (childWithAccessibilityFocus != child) { continue; } childWithAccessibilityFocus = null; i = childrenCount - 1; } // X 控件范围 A , 如果手指按在 B 范围 , 不会触发 X 控件的事件 // 判定当前的组件是否可见 , 是否处于动画过程中 // ① canViewReceivePointerEvents 判定组件是否可见 , 会否处于动画 // ② isTransformedTouchPointInView 判定手指是否在控件上面 ; // 上述两种情况 , 不触发事件 if (!canViewReceivePointerEvents(child) || !isTransformedTouchPointInView(x, y, child, null)) { ev.setTargetAccessibilityFocus(false); // 不触发事件 continue; } // 截止到此处 , 可以获取子组件进行操作 // 提取当前的子组件 // 第一次执行 getTouchTarget 代码时 , 是没有 mFirstTouchTarget 的 // 此时第一次返回 null newTouchTarget = getTouchTarget(child); // 该分支操作第一次不执行 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); // 正式开始分发触摸事件 // 处理以下两种情况 : // ① 情况一 : 子控件触摸事件返回 true // ② 情况二 : 子控件触摸事件返回 false 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 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) { // 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; } @Override public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) { // disallowIntercept 存在一个默认值 , 如果值为默认值 , 直接退出 if (disallowIntercept == ((mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0)) { // We're already in this state, assume our ancestors are too return; } // 如果不是默认值 , 则进行相应更改 // 最终的值影响 mGroupFlags 是 true 还是 false if (disallowIntercept) { mGroupFlags |= FLAG_DISALLOW_INTERCEPT; } else { mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT; } // Pass it up to our parent if (mParent != null) { mParent.requestDisallowInterceptTouchEvent(disallowIntercept); } } public boolean onInterceptTouchEvent(MotionEvent ev) { // 该方法只返回是否进行事件拦截 , 返回一个布尔值 , 没有进行具体的事件拦截 if (ev.isFromSource(InputDevice.SOURCE_MOUSE) && ev.getAction() == MotionEvent.ACTION_DOWN && ev.isButtonPressed(MotionEvent.BUTTON_PRIMARY) && isOnScrollbarThumb(ev.getX(), ev.getY())) { return true; } return false; } /** * Provide custom ordering of views in which the touch will be dispatched. * 按照事件传递的顺序进行组件排序 * * This is called within a tight loop, so you are not allowed to allocate objects, including * the return array. Instead, you should return a pre-allocated list that will be cleared * after the dispatch is finished. * @hide */ public ArrayList<View> buildTouchDispatchChildList() { return buildOrderedChildList(); } /** * Populates (and returns) mPreSortedChildren with a pre-ordered list of the View's children, * sorted first by Z, then by child drawing order (if applicable). This list must be cleared * after use to avoid leaking child Views. * * Uses a stable, insertion sort which is commonly O(n) for ViewGroups with very few elevated * children. */ ArrayList<View> buildOrderedChildList() { final int childrenCount = mChildrenCount; if (childrenCount <= 1 || !hasChildWithZ()) return null; if (mPreSortedChildren == null) { mPreSortedChildren = new ArrayList<>(childrenCount); } else { // callers should clear, so clear shouldn't be necessary, but for safety... mPreSortedChildren.clear(); mPreSortedChildren.ensureCapacity(childrenCount); } final boolean customOrder = isChildrenDrawingOrderEnabled(); // 下面的组件排序的核心逻辑 // 获取当前所有组件的子组件的 Z 轴的深度 // 按照 Z 轴深度进行排序 // Z 轴方向上 , 对于事件传递 , 上面的组件优先级高于被覆盖的下面的组件优先级 for (int i = 0; i < childrenCount; i++) { // add next child (in child order) to end of list final int childIndex = getAndVerifyPreorderedIndex(childrenCount, i, customOrder); final View nextChild = mChildren[childIndex]; final float currentZ = nextChild.getZ(); // insert ahead of any Views with greater Z // 计算当前遍历的组件应该被放到的索引位置 int insertIndex = i; while (insertIndex > 0 && mPreSortedChildren.get(insertIndex - 1).getZ() > currentZ) { insertIndex--; } // 将当前遍历的组件插入到指定索引位置上 mPreSortedChildren.add(insertIndex, nextChild); } return mPreSortedChildren; } // 获取排序后的子组件的索引值 private int getAndVerifyPreorderedIndex(int childrenCount, int i, boolean customOrder) { final int childIndex; if (customOrder) { final int childIndex1 = getChildDrawingOrder(childrenCount, i); if (childIndex1 >= childrenCount) { throw new IndexOutOfBoundsException("getChildDrawingOrder() " + "returned invalid index " + childIndex1 + " (child count is " + childrenCount + ")"); } childIndex = childIndex1; } else { childIndex = i; } return childIndex; } // 获取索引值对应的组件 private static View getAndVerifyPreorderedView(ArrayList<View> preorderedList, View[] children, int childIndex) { final View child; if (preorderedList != null) { child = preorderedList.get(childIndex); if (child == null) { throw new RuntimeException("Invalid preorderedList contained null child at index " + childIndex); } } else { child = children[childIndex]; } return child; } /** * Returns true if a child view can receive pointer events. * 判定控件是否可见 / 是否处于动画中 * @hide */ private static boolean canViewReceivePointerEvents(@NonNull View child) { return (child.mViewFlags & VISIBILITY_MASK) == VISIBLE || child.getAnimation() != null; } /** * Returns true if a child view contains the specified point when transformed * into its coordinate space. * Child must not be null. * 判定手指是否触摸到了组件 , 是否在组件区域范围内 * @hide */ protected boolean isTransformedTouchPointInView(float x, float y, View child, PointF outLocalPoint) { // 获取当前坐标 final float[] point = getTempPoint(); point[0] = x; point[1] = y; transformPointToViewLocal(point, child); final boolean isInView = child.pointInView(point[0], point[1]); if (isInView && outLocalPoint != null) { outLocalPoint.set(point[0], point[1]); } return isInView; } /** * Gets the touch target for specified child view. * Returns null if not found. * */ private TouchTarget getTouchTarget(@NonNull View child) { // 判断 mFirstTouchTarget 中的 child 字段 , 是否是当前遍历的 子组件 View // 如果是 , 则返回该 TouchTarget // 如果不是 , 则返回空 for (TouchTarget target = mFirstTouchTarget; target != null; target = target.next) { if (target.child == child) { return target; } } return null; } /** * Transforms a motion event into the coordinate space of a particular child view, * filters out irrelevant pointer ids, and overrides its action if necessary. * If child is null, assumes the MotionEvent will be sent to this ViewGroup instead. * 该方法是正式分发触摸事件的方法 * 注意参数中传入了当前正在被遍历的 child 子组件 */ 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. // 处理取消状态 , 暂时不分析 ; 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) { // 被遍历的 child 子组件为空 // 调用父类的分发方法 handled = super.dispatchTouchEvent(event); } else { // 被遍历的 child 子组件不为空 final float offsetX = mScrollX - child.mLeft; final float offsetY = mScrollY - child.mTop; event.offsetLocation(offsetX, offsetY); // 子组件分发触摸事件 // 此处调用的是 View 组件的 dispatchTouchEvent 方法 ; 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; } }
源码路径 : /frameworks/base/core/java/android/view/ViewGroup.java