02.Activity的事件分发机制php
03.ViewGroup事件的分发机制android
04.View事件的分发机制git
05.思考一下github
02.View事件分发场景segmentfault
03.View事件机制源码分析markdown
04.View事件机制ide
07.View事件总结1源码分析
Android中事件分发顺序:
其中:
充分理解Android分发机制,本质上是要理解:
当一个点击事件发生时,事件最早传到Activity的dispatchTouchEvent()进行事件分发
咱们来看下Activity的dispatchTouchEvent()的源码
public boolean dispatchTouchEvent(MotionEvent ev) { //第一步 //通常事件列开始都是DOWN,因此这里基本是true if (ev.getAction() == MotionEvent.ACTION_DOWN) { //第二步 onUserInteraction(); } //第三步 if (getWindow().superDispatchTouchEvent(ev)) { return true; } return onTouchEvent(ev); }
第一步
第二步
public void onUserInteraction() { }
从源码能够看出:
第三步
@Override public boolean superDispatchTouchEvent(MotionEvent event) { return mDecor.superDispatchTouchEvent(event); //mDecor是DecorView的实例 //DecorView是视图的顶层view,继承自FrameLayout,是全部界面的父类 }
接下来咱们看mDecor.superDispatchTouchEvent(event):
public boolean superDispatchTouchEvent(MotionEvent event) { return super.dispatchTouchEvent(event); //DecorView继承自FrameLayout //那么它的父类就是ViewGroup 而super.dispatchTouchEvent(event)方法,其实就应该是ViewGroup的dispatchTouchEvent() }
得出结果
当一个点击事件发生时,调用顺序以下
布局以下:
结果测试
从上面的测试结果发现:
ViewGroup的dispatchTouchEvent()源码分析,该方法比较复杂,截取几个重要的逻辑片断进行介绍,来解析整个分发流程。
// 发生ACTION_DOWN事件或者已经发生过ACTION_DOWN,而且将mFirstTouchTarget赋值,才进入此区域,主要功能是拦截器 final boolean intercepted; if (actionMasked == MotionEvent.ACTION_DOWN|| mFirstTouchTarget != null) { //disallowIntercept:是否禁用事件拦截的功能(默认是false),即不由用 //能够在子View经过调用requestDisallowInterceptTouchEvent方法对这个值进行修改,不让该View拦截事件 final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0; //默认状况下会进入该方法 if (!disallowIntercept) { //调用拦截方法 intercepted = onInterceptTouchEvent(ev); ev.setAction(action); } else { intercepted = false; } } else { // 当没有触摸targets,且不是down事件时,开始持续拦截触摸。 intercepted = true; }
当ViewGroup不拦截事件的时候,事件会向下分发交由它的子View或ViewGroup进行处理。
/* 从最底层的父视图开始遍历, ** 找寻newTouchTarget,即上面的mFirstTouchTarget ** 若是已经存在找寻newTouchTarget,说明正在接收触摸事件,则跳出循环。 */ for (int i = childrenCount - 1; i >= 0; i--) { final int childIndex = customOrder ? getChildDrawingOrder(childrenCount, i) : i; final View child = (preorderedList == null) ? children[childIndex] : preorderedList.get(childIndex); // 若是当前视图没法获取用户焦点,则跳过本次循环 if (childWithAccessibilityFocus != null) { if (childWithAccessibilityFocus != child) { continue; } childWithAccessibilityFocus = null; i = childrenCount - 1; } //若是view不可见,或者触摸的坐标点不在view的范围内,则跳过本次循环 if (!canViewReceivePointerEvents(child) || !isTransformedTouchPointInView(x, y, child, null)) { ev.setTargetAccessibilityFocus(false); continue; } newTouchTarget = getTouchTarget(child); // 已经开始接收触摸事件,并退出整个循环。 if (newTouchTarget != null) { newTouchTarget.pointerIdBits |= idBitsToAssign; break; } //重置取消或抬起标志位 //若是触摸位置在child的区域内,则把事件分发给子View或ViewGroup if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) { // 获取TouchDown的时间点 mLastTouchDownTime = ev.getDownTime(); // 获取TouchDown的Index if (preorderedList != null) { for (int j = 0; j < childrenCount; j++) { if (children[childIndex] == mChildren[j]) { mLastTouchDownIndex = j; break; } } } else { mLastTouchDownIndex = childIndex; } //获取TouchDown的x,y坐标 mLastTouchDownX = ev.getX(); mLastTouchDownY = ev.getY(); //添加TouchTarget,则mFirstTouchTarget != null。 newTouchTarget = addTouchTarget(child, idBitsToAssign); //表示以及分发给NewTouchTarget alreadyDispatchedToNewTouchTarget = true; break; }
dispatchTransformedTouchEvent()
方法实际就是调用子元素的dispatchTouchEvent()
方法。dispatchTransformedTouchEvent()
方法的重要逻辑以下:if (child == null) { handled = super.dispatchTouchEvent(event); } else { handled = child.dispatchTouchEvent(event); }
//添加TouchTarget,则mFirstTouchTarget != null。 newTouchTarget = addTouchTarget(child, idBitsToAssign); //表示以及分发给NewTouchTarget alreadyDispatchedToNewTouchTarget = true;
addTouchTarget(child, idBitsToAssign);
内部完成mFirstTouchTarget被赋值。若是mFirstTouchTarget为空,将会让ViewGroup默认拦截全部操做。若是遍历全部子View或ViewGroup,都没有消费事件。ViewGroup会本身处理事件。在ViewGroup中经过onInterceptTouchEvent()对事件传递进行拦截
View中dispatchTouchEvent()的源码分析
public boolean dispatchTouchEvent(MotionEvent event) { if (mOnTouchListener != null && (mViewFlags & ENABLED_MASK) == ENABLED && mOnTouchListener.onTouch(this, event)) { return true; } return onTouchEvent(event); }
从上面能够看出:
第一个条件:mOnTouchListener != null; 第二个条件:(mViewFlags & ENABLED_MASK) == ENABLED; 第三个条件:mOnTouchListener.onTouch(this, event);
下面,咱们来看看下这三个判断条件:
//mOnTouchListener是在View类下setOnTouchListener方法里赋值的 public void setOnTouchListener(OnTouchListener l) { //即只要咱们给控件注册了Touch事件,mOnTouchListener就必定被赋值(不为空) mOnTouchListener = l; }
//手动调用设置 button.setOnTouchListener(new OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { return false; } });
接下来,咱们继续看:onTouchEvent(event)的源码分析
public boolean onTouchEvent(MotionEvent event) { final int viewFlags = mViewFlags; if ((viewFlags & ENABLED_MASK) == DISABLED) { // A disabled view that is clickable still consumes the touch // events, it just doesn't respond to them. return (((viewFlags & CLICKABLE) == CLICKABLE || (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)); } if (mTouchDelegate != null) { if (mTouchDelegate.onTouchEvent(event)) { return true; } } //若是该控件是能够点击的就会进入到下两行的switch判断中去; if (((viewFlags & CLICKABLE) == CLICKABLE || (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)) { //若是当前的事件是抬起手指,则会进入到MotionEvent.ACTION_UP这个case当中。 switch (event.getAction()) { case MotionEvent.ACTION_UP: boolean prepressed = (mPrivateFlags & PREPRESSED) != 0; // 在通过种种判断以后,会执行到关注点1的performClick()方法。 //请往下看关注点1 if ((mPrivateFlags & PRESSED) != 0 || prepressed) { // take focus if we don't have it already and we should in // touch mode. boolean focusTaken = false; if (isFocusable() && isFocusableInTouchMode() && !isFocused()) { focusTaken = requestFocus(); } if (!mHasPerformedLongPress) { // This is a tap, so remove the longpress check removeLongPressCallback(); // Only perform take click actions if we were in the pressed state if (!focusTaken) { // Use a Runnable and post this rather than calling // performClick directly. This lets other visual state // of the view update before click actions start. if (mPerformClick == null) { mPerformClick = new PerformClick(); } if (!post(mPerformClick)) { //关注点1 //请往下看performClick()的源码分析 performClick(); } } } if (mUnsetPressedState == null) { mUnsetPressedState = new UnsetPressedState(); } if (prepressed) { mPrivateFlags |= PRESSED; refreshDrawableState(); postDelayed(mUnsetPressedState, ViewConfiguration.getPressedStateDuration()); } else if (!post(mUnsetPressedState)) { // If the post failed, unpress right now mUnsetPressedState.run(); } removeTapCallback(); } break; case MotionEvent.ACTION_DOWN: if (mPendingCheckForTap == null) { mPendingCheckForTap = new CheckForTap(); } mPrivateFlags |= PREPRESSED; mHasPerformedLongPress = false; postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout()); break; case MotionEvent.ACTION_CANCEL: mPrivateFlags &= ~PRESSED; refreshDrawableState(); removeTapCallback(); break; case MotionEvent.ACTION_MOVE: final int x = (int) event.getX(); final int y = (int) event.getY(); // Be lenient about moving outside of buttons int slop = mTouchSlop; if ((x < 0 - slop) || (x >= getWidth() + slop) || (y < 0 - slop) || (y >= getHeight() + slop)) { // Outside button removeTapCallback(); if ((mPrivateFlags & PRESSED) != 0) { // Remove any future long press/tap checks removeLongPressCallback(); // Need to switch from pressed to not pressed mPrivateFlags &= ~PRESSED; refreshDrawableState(); } } break; } //若是该控件是能够点击的,就必定会返回true return true; } //若是该控件是不能够点击的,就必定会返回false return false; }
关注点1:
public boolean performClick() { sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED); if (mOnClickListener != null) { playSoundEffect(SoundEffectConstants.CLICK); mOnClickListener.onClick(this); return true; } return false; }
那么,mOnClickListener又是在哪里赋值的呢?请继续看:
public void setOnClickListener(OnClickListener l) { if (!isClickable()) { setClickable(true); } mOnClickListener = l; }
2.每当控件被点击时:
若是在回调onTouch()里返回false,就会让dispatchTouchEvent方法返回false,那么就会执行onTouchEvent();若是回调了setOnClickListener()来给控件注册点击事件的话,最后会在performClick()方法里回调onClick()。
若是在回调onTouch()里返回true,就会让dispatchTouchEvent方法返回true,那么将不会执行onTouchEvent(),即onClick()也不会执行;
在回调onTouch()里返回true
TextView textView = findViewById(R.id.tv_13); //设置OnTouchListener() textView.setOnTouchListener(new View.OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { Log.d("小杨逗比","执行了onTouch(), 动做是:" + event.getAction()); return true; } }); //设置OnClickListener textView.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Log.d("小杨逗比","执行了onClick()"); } });
2019-04-04 13:37:58.301 13616-13616/org.yczbj.ycrefreshview D/小杨逗比: 执行了onTouch(), 动做是:0 2019-04-04 13:37:58.315 13616-13616/org.yczbj.ycrefreshview D/小杨逗比: 执行了onTouch(), 动做是:2 2019-04-04 13:37:58.405 13616-13616/org.yczbj.ycrefreshview D/小杨逗比: 执行了onTouch(), 动做是:2 2019-04-04 13:37:58.408 13616-13616/org.yczbj.ycrefreshview D/小杨逗比: 执行了onTouch(), 动做是:1
在回调onTouch()里返回false
2019-04-04 13:41:26.961 14006-14006/org.yczbj.ycrefreshview D/小杨逗比: 执行了onTouch(), 动做是:0 2019-04-04 13:41:26.978 14006-14006/org.yczbj.ycrefreshview D/小杨逗比: 执行了onTouch(), 动做是:2 2019-04-04 13:41:27.072 14006-14006/org.yczbj.ycrefreshview D/小杨逗比: 执行了onTouch(), 动做是:2 2019-04-04 13:41:27.074 14006-14006/org.yczbj.ycrefreshview D/小杨逗比: 执行了onTouch(), 动做是:1 2019-04-04 13:41:27.076 14006-14006/org.yczbj.ycrefreshview D/小杨逗比: 执行了onClick()
特别注意:请看下面代码
//&&为短路与,即若是前面条件为false,将再也不往下执行 //因此,onTouch可以获得执行须要两个前提条件: //1. mOnTouchListener的值不能为空 //2. 当前点击的控件必须是enable的。 mOnTouchListener != null && (mViewFlags & ENABLED_MASK) == ENABLED && mOnTouchListener.onTouch(this, event)
当dispatchTouchEvent在进行事件分发的时候,只有前一个事件(如ACTION_DOWN)返回true,才会收到后一个事件(ACTION_MOVE和ACTION_UP)
从上面对事件分发机制分析知:
这里给出ACTION_MOVE和ACTION_UP事件的传递结论: