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 ;
代码语言：javascript复制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 ;
代码语言：javascript复制 // 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 ;
代码语言：javascript复制 /**
* 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 ;
代码语言：javascript复制 /**
* 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
个条件只要存在
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 ;
代码语言：javascript复制 // 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 :
代码语言：javascript复制@UiThread
public abstract class ViewGroup extends View implements ViewParent, ViewManager {
@Override
public 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 ;
代码语言：javascript复制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
代码语言：javascript复制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 ;
代码语言：javascript复制 // 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 :
代码语言：javascript复制@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 ;
代码语言：javascript复制@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
