事件传递
Activity
public boolean dispatchTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
onUserInteraction();
}
//事件交给window分发处理,如果window没有消耗事件,则activity的onTouchEvent处理事件
if (getWindow().superDispatchTouchEvent(ev)) {
return true;
}
return onTouchEvent(ev);
}
public boolean onTouchEvent(MotionEvent event) {
if (mWindow.shouldCloseOnTouch(this, event)) {
finish();
return true;
}
return false;
}
window的实体PhoneWindow
@Override
public boolean superDispatchTouchEvent(MotionEvent event) {
//事件交给了DecorView,我们知道DecorView是一个FrameLayout,即事件交给了ViewGroup
return mDecor.superDispatchTouchEvent(event);
}
View系统
viewGroup
public boolean dispatchTouchEvent(MotionEvent ev) {
if (onFilterTouchEventForSecurity(ev)) {
//只有down事件才走流程判断(因为一个事件的开始就是down),
//FLAG_DISALLOW_INTERCEPT是子view requestDisallowInterceptTouchEvent()控制的,即子view请求父类是否拦截
if (actionMasked == MotionEvent.ACTION_DOWN || mFirstTouchTarget != null) {
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
if (!disallowIntercept) {
**//先判断是否拦截**
intercepted = onInterceptTouchEvent(ev);
ev.setAction(action); // restore action in case it was changed
} else {
intercepted = false;
}
} else {
intercepted = true;
}
}
}
//子view请求父类是否拦截
public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) {
if (disallowIntercept == ((mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0)) {
// We're already in this state, assume our ancestors are too
return;
}
if (disallowIntercept) {
mGroupFlags |= FLAG_DISALLOW_INTERCEPT;
} else {
mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT;
}
//递归父类
if (mParent != null) {
mParent.requestDisallowInterceptTouchEvent(disallowIntercept);
}
}
public boolean dispatchTouchEvent(MotionEvent ev) {
if (!canceled && !intercepted) {
final int childrenCount = mChildrenCount;
if (newTouchTarget == null && childrenCount != 0) {
//这里api注释说,在vg里从前到后查询能接收事件的child
//即有俩个关键点1:从前到后,说明是vg中view是有顺序的
//2.能接收事件,说明不是所有child都能接收,那么这个能力怎么来的
final ArrayList<View> preorderedList = buildTouchDispatchChildList();
final boolean customOrder = preorderedList == null && isChildrenDrawingOrderEnabled();
//1.vg中child的顺序,我们知道我们addview的时候可以添加index
final View[] children = mChildren;
for (int i = childrenCount - 1; i >= 0; i--) {
//2.接收能力
final int childIndex = getAndVerifyPreorderedIndex(childrenCount, i, customOrder);
final View child = getAndVerifyPreorderedView(preorderedList, children, childIndex);
**vg不拦截,然后传给child分发**
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;
}
}
}
}
vg中
private View[] mChildren;成员变量,保存所有child
private int mChildrenCount;保存所有child数量
mChildren的创建和添加
addView()-->addViewInner()-->addInArray()
private void addInArray(View child, int index) {
View[] children = mChildren;
final int count = mChildrenCount;
final int size = children.length;
//索引从0开始,即 索引 = 数量 -1
//当前要添加的child索引是最后一个,直接add到最后一个
if (index == count) {
if (size == count) {
//扩容
mChildren = new View[size + ARRAY_CAPACITY_INCREMENT];
System.arraycopy(children, 0, mChildren, 0, size);
children = mChildren;
}
children[mChildrenCount++] = child;
//当前要添加的child索引是不最后一个,证明是插入
} else if (index < count) {
if (size == count) {
mChildren = new View[size + ARRAY_CAPACITY_INCREMENT];
System.arraycopy(children, 0, mChildren, 0, index);
System.arraycopy(children, index, mChildren, index + 1, count - index);
children = mChildren;
} else {
System.arraycopy(children, index, children, index + 1, count - index);
}
children[index] = child;
mChildrenCount++;
if (mLastTouchDownIndex >= index) {
mLastTouchDownIndex++;
}
} else {
//索引越界
throw new IndexOutOfBoundsException("index=" + index + " count=" + count);
}
}
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();
}
} else {
child = children[childIndex];
}
return child;
}
关键在于preorderedList
ArrayList<View> buildOrderedChildList() {
final int childrenCount = mChildrenCount;
if (childrenCount <= 1 || !hasChildWithZ()) return null;
//不存在创建
if (mPreSortedChildren == null) {
mPreSortedChildren = new ArrayList<>(childrenCount);
} else {
//存在为了安全起见,扩容
mPreSortedChildren.clear();
mPreSortedChildren.ensureCapacity(childrenCount);
}
final boolean customOrder = isChildrenDrawingOrderEnabled();
//按照顺寻添加到临时托儿所中
for (int i = 0; i < childrenCount; i++) {
//获取具备接收事件的child
final int childIndex = getAndVerifyPreorderedIndex(childrenCount, i, customOrder);
final View nextChild = mChildren[childIndex];
final float currentZ = nextChild.getZ();
//按照的这个z轴排序,前面我们分析activity和window都有z轴概念,即图层
int insertIndex = i;
while (insertIndex > 0 && mPreSortedChildren.get(insertIndex - 1).getZ() > currentZ) {
insertIndex--;
}
mPreSortedChildren.add(insertIndex, nextChild);
}
return mPreSortedChildren;
}
//临时托儿所,专门管理vg中child的
private ArrayList<View> mPreSortedChildren;
/**
* 指示ViewGroup是否按定义的顺序绘制其子元素 false otherwise
*
* @see #setChildrenDrawingOrderEnabled(boolean)
* @see #getChildDrawingOrder(int, int)
*/
@ViewDebug.ExportedProperty(category = "drawing")
protected boolean isChildrenDrawingOrderEnabled() {
return (mGroupFlags & FLAG_USE_CHILD_DRAWING_ORDER) == FLAG_USE_CHILD_DRAWING_ORDER;
}
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();
}
childIndex = childIndex1;
} else {
childIndex = i;
}
return childIndex;
}
public boolean dispatchTouchEvent(MotionEvent ev) {
**拦截事件,自己处理**
if (mFirstTouchTarget == null) {
handled = dispatchTransformedTouchEvent(ev, canceled, null,TouchTarget.ALL_POINTER_IDS);
} else {
dispatchTransformedTouchEvent(ev, cancelChild,target.child, target.pointerIdBits)
}
}
因为vg拦截事件自己处理,和不拦截事件child处理都会走这个方法,只能通过参数看不同了
其中参数View child是重点
private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,
View child, int desiredPointerIdBits) {
final boolean handled;
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;
}
final int oldPointerIdBits = event.getPointerIdBits();
final int newPointerIdBits = oldPointerIdBits & desiredPointerIdBits;
if (newPointerIdBits == 0) {
return false;
}
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);
}
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;
}
上面方法,可见如果Child存在,就把事件传给child做,否则就传给super(View,vg继承自View,即传给自己处理)
除此之外还有一个如果是cancel事件,直接处理,其他事件还要进行一次处理,介于MotionEvent都是native的方法,等我有能力再说
但是不管怎么说,都是把事件传给了childView,或者selfView的分发
view
public boolean dispatchTouchEvent(MotionEvent event) {
...稍后
if (onFilterTouchEventForSecurity(event)) {
if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {
result = true;
}
ListenerInfo li = mListenerInfo;
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
result = true;
}
if (!result && onTouchEvent(event)) {
result = true;
}
}
...稍后
}
对事件进行过滤,判断是窗体是否被遮盖,如果没有被遮盖即可以进行事件处理流程
判断enable属性和是否设置了onTouchListener,以及OnTouchListener.onTouch的返回值
如果enable=true,OnTouchListener.onTouch=true,则不会调用该view的onTouchEvent处理事件
否则事件交给view的onTouchEvent处理
理解分发的逻辑流程,需要先了解一下内容:
1.view的属性enable,可以在布局中设置,也可以在代码中设置
//enable = true的值
static final int ENABLED = 0x00000000;
//enable = false的值
static final int DISABLED = 0x00000020;
//enable默认值false
static final int ENABLED_MASK = 0x00000020;
从源码中(mViewFlags & ENABLED_MASK) == ENABLED可以看出,view的enable属性是用mViewFlags保存的
mViewFlags的由来(view源码)
public View(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
this(context);
布局属性获取
final TypedArray a = context.obtainStyledAttributes(
attrs, com.android.internal.R.styleable.View, defStyleAttr, defStyleRes);
final int N = a.getIndexCount();
for (int i = 0; i < N; i++) {
int attr = a.getIndex(i);
switch (attr) {
case com.android.internal.R.styleable.View_background:
background = a.getDrawable(attr);
break;
case com.android.internal.R.styleable.View_padding:
padding = a.getDimensionPixelSize(attr, -1);
mUserPaddingLeftInitial = padding;
mUserPaddingRightInitial = padding;
leftPaddingDefined = true;
rightPaddingDefined = true;
break;
......
}
}
if (viewFlagMasks != 0) {
setFlags(viewFlagValues, viewFlagMasks);
}
}
void setFlags(int flags, int mask) {
mViewFlags = (mViewFlags & ~mask) | (flags & mask);
}
可以看到mViewFlags是view的属性进行一系列的位运算得到的。而mViewFlags与ENABLED_MASK的位运算就是获取enable属性的值
2.view的内部类ListenerInfo,封装了所有view的监听功能的对象,我们设置监听即是给这个静态内部类的成员赋值的过程,而回调也是
view通过ListenerInfo获取到对应的监听器,然后回调
比如
public void setOnScrollChangeListener(OnScrollChangeListener l) {
getListenerInfo().mOnScrollChangeListener = l;
}
ListenerInfo getListenerInfo() {
if (mListenerInfo != null) {
return mListenerInfo;
}
mListenerInfo = new ListenerInfo();
return mListenerInfo;
}
if (mListenerInfo != null && mListenerInfo.mOnScrollChangeListener != null) {
mListenerInfo.mOnScrollChangeListener.onScrollChange(this, l, t, oldl, oldt);
}
ListenerInfo内部具体的监听器:
static class ListenerInfo {
//光标变化
protected OnFocusChangeListener mOnFocusChangeListener;
//布局变化,不止一个,所以是集合保存,add添加,remove移除等
private ArrayList<OnLayoutChangeListener> mOnLayoutChangeListeners;
//滑动变化
protected OnScrollChangeListener mOnScrollChangeListener;
//view挂接和断开window的监听 onViewAttachedToWindow(View v),onViewDetachedFromWindow(View v)
private CopyOnWriteArrayList<OnAttachStateChangeListener> mOnAttachStateChangeListeners;
//点击监听
public OnClickListener mOnClickListener;
//长点击监听
protected OnLongClickListener mOnLongClickListener;
//api 23新增的上下文点击监听(为什么要加上下文?)
protected OnContextClickListener mOnContextClickListener;
//创建上下文菜单监听onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo)
protected OnCreateContextMenuListener mOnCreateContextMenuListener;
//键盘事件
private OnKeyListener mOnKeyListener;
//触摸事件
private OnTouchListener mOnTouchListener;
//悬浮事件,html的鼠标悬浮
private OnHoverListener mOnHoverListener;
//任意的手势时回调
private OnGenericMotionListener mOnGenericMotionListener;
//当view被拖动时回调
private OnDragListener mOnDragListener;
//监控并动态控制到SystemUi(状态栏)的显示与隐藏,setSystemUiVisibility(int visibility)
private OnSystemUiVisibilityChangeListener mOnSystemUiVisibilityChangeListener;
OnApplyWindowInsetsListener mOnApplyWindowInsetsListener;
//api 26新增 指针捕获监听....
OnCapturedPointerListener mOnCapturedPointerListener;
}
3.onFilterTouchEventForSecurity(event)事件过滤,判断是否需要进行事件分发逻辑
public boolean onFilterTouchEventForSecurity(MotionEvent event) {
//如果窗体被覆盖,被遮挡。此时的窗体是window呢还是view
if ((mViewFlags & FILTER_TOUCHES_WHEN_OBSCURED) != 0
&& (event.getFlags() & MotionEvent.FLAG_WINDOW_IS_OBSCURED) != 0) {
return false;
}
return true;
}
4.handleScrollBarDragging(event)
在看返回的boolean值,发现分发的返回值都是onTouchEvent或者listener回调的onTouch的返回值。
即控制上一层能不能处理事件
遗留问题:事件怎么产生?事件MotionEvent是个啥?native的东西怎么搞?
总结
不论多少层view嵌套
事件都是从最外层(最大层)开始分发传递,所以找好复杂的问题分析的源头
viewGroup才有拦截方法,拦截方法可以控制事件分发方法,但是拦截也是受到约束的,比如子层可以申请不被拦截requestDisallowInterceptTouchEvent
viewgroup继承自view,所以即使事件被拦截,vg要走view的分发方法,转给onTouchEvent处理(自己处理事件)
而setOnTouchListener的返回值会优先决定是否会走onTouchEvent方法的,同时setOnTouchListener也会受到属性enable的影响
事件被传到下一层处理完毕后,能否再传回到上层处理的决定者是onTouchEvent或者setOnTouchListene.onTouch的返回值