Android 事件分发 系列文章目录
【Android 事件分发】事件分发源码分析 ( 驱动层通过中断传递事件 | WindowManagerService 向 View 层传递事件 )
【Android 事件分发】事件分发源码分析 ( Activity 中各层级的事件传递 | Activity -＞ PhoneWindow -＞ DecorView -＞ ViewGroup )
【Android 事件分发】事件分发源码分析 ( ViewGroup 事件传递机制 一 )
【Android 事件分发】事件分发源码分析 ( ViewGroup 事件传递机制 二 )
【Android 事件分发】事件分发源码分析 ( ViewGroup 事件传递机制 三 )
文章目录
Android 事件分发 系列文章目录前言一、获取子组件二、当前遍历的子组件的事件分发三、ViewGroup 事件分发相关源码前言
接上一篇博客 【Android 事件分发】事件分发源码分析 ( ViewGroup 事件传递机制 二 ) , 继续分析 ViewGroup 的事件分发机制后续代码 ;
一、获取子组件
之前已经按照 Z 轴深度 , 将组件进行排序 , 放在集合中 ;
倒序遍历排列好的组件 , 按照 Z 轴的上下顺序 , 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--) {
先获取组件索引 , 然后获取索引对应的子组件 ;
// 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);
然后判定组件是否符合要求 :
调用 canViewReceivePointerEvents 方法 , 判定组件是否可见 , 会否处于动画中 ;
/*** 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;}
调用 isTransformedTouchPointInView 判定手指是否在控件上面 ;
/*** 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;}
如果上面 333 个条件只要存在 111 个不满足 , 则不传递触摸事件 , 在遍历时直接 continue , 越过该控件 , 遍历下一个控件 ;
// 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;}
ViewGroup | dispatchTouchEvent 方法相关源码 :
@UiThreadpublic abstract class ViewGroup extends View implements ViewParent, ViewManager {@Overridepublic boolean dispatchTouchEvent(MotionEvent ev) {...// 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 ...}/*** 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;}}
源码路径 :/frameworks/base/core/java/android/view/ViewGroup.java
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 :
@UiThreadpublic abstract class ViewGroup extends View implements ViewParent, ViewManager {@Overridepublic 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 ;
@UiThreadpublic abstract class ViewGroup extends View implements ViewParent, ViewManager {// First touch target in the linked list of touch targets.private TouchTarget mFirstTouchTarget;@Overridepublic 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 downfinal 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 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 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;}@Overridepublic 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 tooreturn;}// 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 parentif (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 listfinal 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
