Android 事件分发事件分发源码分析 ( ViewGroup 事件传递机制 二 )
Posted 韩曙亮
tags:
篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了Android 事件分发事件分发源码分析 ( ViewGroup 事件传递机制 二 )相关的知识，希望对你有一定的参考价值。
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 )
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 一 ) , 继续分析 ViewGroup 的事件分发机制后续代码 ;
一、获取触摸索引值
首先在 动作事件不是取消操作 , 且不拦截事件 , 的前提下 , 才能执行后续操作 , 判定代码如下 :
// 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) {
凡是涉及到 Accessibility 功能的 , 直接忽略 , 与当前分析的事件分发无关 ;
View childWithAccessibilityFocus = ev.isTargetAccessibilityFocus()
? findChildWithAccessibilityFocus() : null;
再次判定是否是按下操作 ;
// 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) {
如果是按下操作 , 则获取触摸索引值 , 从 0 开始计数 ;
// 获取触摸索引值
final int actionIndex = ev.getActionIndex(); // always 0 for down
ViewGroup | dispatchTouchEvent 方法相关源码 :
@UiThread
public abstract class ViewGroup extends View implements ViewParent, ViewManager {
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
...
// 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);
...
}
}
源码路径 : /frameworks/base/core/java/android/view/ViewGroup.java
二、按照 Z 轴深度排序组件
先计算 ViewGroup 父容器下面有多少个子 View 组件 ;
// 计算 ViewGroup 父容器下面有多少个子 View 组件 ;
final int childrenCount = mChildrenCount;
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 ;
在子组件个数不为 0 的情况下 , 继续向后执行 ;
获取手指触摸的 x, y 坐标值 ;
// 获取单个手指的 x,y 坐标
final float x = ev.getX(actionIndex);
final float y = ev.getY(actionIndex);
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 ;
// 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();
ViewGroup | buildTouchDispatchChildList 方法是排序的核心方法 ;
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 ;
下面的代码是组件遍历排序的核心逻辑 :
// 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);
}
ViewGroup | dispatchTouchEvent / buildOrderedChildList 方法相关源码 :
@UiThread
public abstract class ViewGroup extends View implements ViewParent, ViewManager {
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
...
// 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;
...
}
/**
* 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;
}
}
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;
...
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) 以上是关于Android 事件分发事件分发源码分析 ( ViewGroup 事件传递机制 二 )的主要内容，如果未能解决你的问题，请参考以下文章
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 一 )
Android 事件分发事件分发源码分析 ( ViewGroup 事件传递机制 七 )
Android 事件分发事件分发源码分析 ( ViewGroup 事件传递机制 六 )
Android 事件分发ItemTouchHelper 事件分发源码分析 ( 绑定 RecyclerView )
Android 事件分发ItemTouchHelper 源码分析 ( OnItemTouchListener 事件监听器源码分析 )