viewgroup的事件分发
package com.example.administrator.myapplication.view;
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.widget.RelativeLayout;
/**
* Created by Administrator on 2015/11/29.
*/
public class MyRealLayout extends RelativeLayout {
public MyRealLayout(Context context) {
super(context);
}
public MyRealLayout(Context context, AttributeSet attrs) {
super(context, attrs);
}
public MyRealLayout(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
int action = ev.getAction();
switch (action)
{
case MotionEvent.ACTION_DOWN:
Log.e("MyRealLayout", "dispatchTouchEvent ACTION_DOWN");
break;
case MotionEvent.ACTION_MOVE:
Log.e("MyRealLayout", "dispatchTouchEvent ACTION_MOVE");
break;
case MotionEvent.ACTION_UP:
Log.e("MyRealLayout", "dispatchTouchEvent ACTION_UP");
break;
default:
break;
}
boolean b = super.dispatchTouchEvent(ev);
Log.e("MyRealLayout", "dispatchTouchEvent==="+b);
return b;
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
int action = ev.getAction();
switch (action)
{
case MotionEvent.ACTION_DOWN:
Log.e("MyRealLayout", "onInterceptTouchEvent ACTION_DOWN");
break;
case MotionEvent.ACTION_MOVE:
Log.e("MyRealLayout", "onInterceptTouchEvent ACTION_MOVE");
break;
case MotionEvent.ACTION_UP:
Log.e("MyRealLayout", "onInterceptTouchEvent ACTION_UP");
break;
default:
break;
}
boolean b = super.onInterceptTouchEvent(ev);
Log.e("MyRealLayout", "onInterceptTouchEvent==="+b);
return b;
}
@Override
public boolean onTouchEvent(MotionEvent event) {
int action = event.getAction();
switch (action)
{
case MotionEvent.ACTION_DOWN:
Log.e("MyRealLayout", "onTouchEvent ACTION_DOWN");
break;
case MotionEvent.ACTION_MOVE:
Log.e("MyRealLayout", "onTouchEvent ACTION_MOVE");
break;
case MotionEvent.ACTION_UP:
Log.e("MyRealLayout", "onTouchEvent ACTION_UP");
break;
default:
break;
}
boolean b = super.onTouchEvent(event);
Log.e("MyRealLayout", "onTouchEvent==="+b);
return b;
}
@Override
public void requestDisallowInterceptTouchEvent(boolean disallowIntercept)
{
Log.e("MyRealLayout", "requestDisallowInterceptTouchEvent ");
super.requestDisallowInterceptTouchEvent(disallowIntercept);
}
}
button的点击事件的代码和上篇一样，我们看下log
12-03 10:37:24.876 12965-12965/? E/MyRealLayout: dispatchTouchEvent ACTION_DOWN
12-03 10:37:24.876 12965-12965/? E/MyRealLayout: onInterceptTouchEvent ACTION_DOWN
12-03 10:37:24.876 12965-12965/? E/MyRealLayout: onInterceptTouchEvent===false
12-03 10:37:24.876 12965-12965/? E/MyButton: dispatchTouchEvent ACTION_DOWN
12-03 10:37:24.876 12965-12965/? E/mBtEvent: onTouch ACTION_DOWN
12-03 10:37:24.876 12965-12965/? E/MyButton: onTouchEvent ACTION_DOWN
12-03 10:37:24.877 12965-12965/? E/MyButton: onTouchEvent===true
12-03 10:37:24.877 12965-12965/? E/MyButton: dispatchTouchEvent===true
12-03 10:37:24.877 12965-12965/? E/MyRealLayout: dispatchTouchEvent===true
12-03 10:37:24.923 12965-12965/? E/MyRealLayout: dispatchTouchEvent ACTION_UP
12-03 10:37:24.923 12965-12965/? E/MyRealLayout: onInterceptTouchEvent ACTION_UP
12-03 10:37:24.923 12965-12965/? E/MyRealLayout: onInterceptTouchEvent===false
12-03 10:37:24.923 12965-12965/? E/MyButton: dispatchTouchEvent ACTION_UP
12-03 10:37:24.923 12965-12965/? E/mBtEvent: onTouch ACTION_UP
12-03 10:37:24.923 12965-12965/? E/MyButton: onTouchEvent ACTION_UP
12-03 10:37:24.924 12965-12965/? E/MyButton: onTouchEvent===true
12-03 10:37:24.924 12965-12965/? E/MyButton: dispatchTouchEvent===true
12-03 10:37:24.924 12965-12965/? E/MyRealLayout: dispatchTouchEvent===true
从上面的日志我们可以看出基本的流程是：
MyRealLayout: dispatchTouchEvent ACTION_DOWN=====MyRealLayout: onInterceptTouchEvent ACTION_DOWN==MyButton: dispatchTouchEvent ACTION_DOWN====MyButton: onTouchEvent ACTION_DOWN======
基本就是事件是从父VIEW分发到子viewd的
然后我们进入源码查看：
- ViewGroup - dispatchTouchEvent - ACTION_DOWN
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
if (!onFilterTouchEventForSecurity(ev)) {
return false;
}
//获取当前的动作
final int action = ev.getAction();
final float xf = ev.getX();
final float yf = ev.getY();
//获取view的正确的坐标
final float scrolledXFloat = xf + mScrollX;
final float scrolledYFloat = yf + mScrollY;
final Rect frame = mTempRect;
//判断是否设置不拦截的标志
boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
//将mMotionTarget置为null
if (action == MotionEvent.ACTION_DOWN) {
if (mMotionTarget != null) {
// this is weird, we got a pen down, but we thought it was
// already down!
// XXX: We should probably send an ACTION_UP to the current
// target.``
mMotionTarget = null;
}
//disallowIntercept=true就表示不允许拦截，进入，disallowIntercept 可以通过viewGroup.requestDisallowInterceptTouchEvent(boolean);进行设置是否拦截而onInterceptTouchEvent(ev)我们可以复写自己控制返回值！
// intercept
if (disallowIntercept || !onInterceptTouchEvent(ev)) {
// reset this event's action (just to protect ourselves)
ev.setAction(MotionEvent.ACTION_DOWN);
// We know we want to dispatch the event down, find a child
// who can handle it, start with the front-most child.
final int scrolledXInt = (int) scrolledXFloat;
final int scrolledYInt = (int) scrolledYFloat;
final View[] children = mChildren;
final int count = mChildrenCount;
//开始遍历子view注意这个遍历是倒着遍历的因为最后添加的view肯定在最上面！child.dispatchTouchEvent(ev)
for (int i = count - 1; i >= 0; i--) {
final View child = children[i];
if ((child.mViewFlags & VISIBILITY_MASK) == VISIBLE
|| child.getAnimation() != null) {
child.getHitRect(frame);
//进行判断当前点击的坐标是否包含子view如果包含这个子view就调用
if (frame.contains(scrolledXInt, scrolledYInt)) {
// offset the event to the view's coordinate system
final float xc = scrolledXFloat - child.mLeft;
final float yc = scrolledYFloat - child.mTop;
ev.setLocation(xc, yc);
child.mPrivateFlags &= ~CANCEL_NEXT_UP_EVENT;
//下面就是走view的事件分发流程了
if (child.dispatchTouchEvent(ev)) {
// Event handled, we have a target now.
mMotionTarget = child;
return true;
}
// The event didn't get handled, try the next view.
// Don't reset the event's location, it's not
// necessary here.
}
}
}
}
} //down中做的事情就是判断是否需要拦截事件，如果不需要拦截就遍历字view执行view的分发
- ViewGroup - dispatchTouchEvent - ACTION_UP
public boolean dispatchTouchEvent(MotionEvent ev) {
if (!onFilterTouchEventForSecurity(ev)) {
return false;
}
final int action = ev.getAction();
final float xf = ev.getX();
final float yf = ev.getY();
final float scrolledXFloat = xf + mScrollX;
final float scrolledYFloat = yf + mScrollY;
final Rect frame = mTempRect;
boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
if (action == MotionEvent.ACTION_DOWN) {...}
boolean isUpOrCancel = (action == MotionEvent.ACTION_UP) ||
(action == MotionEvent.ACTION_CANCEL);
//判读当前的事件是否等于up或者ACTION_CANCEL
if (isUpOrCancel) {
mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT;
}
final View target = mMotionTarget;
if(target ==null ){...}
//判断当前的view是否拦截
if (!disallowIntercept && onInterceptTouchEvent(ev)) {...}
if (isUpOrCancel) {
mMotionTarget = null;
}
// finally offset the event to the target's coordinate system and
// dispatch the event.
final float xc = scrolledXFloat - (float) target.mLeft;
final float yc = scrolledYFloat - (float) target.mTop;
ev.setLocation(xc, yc);
return target.dispatchTouchEvent(ev);
}
up的时候主要是重置一些属性。然后在调用dispatchTouchEvent
总结下
- dowun的时候ViewGroup捕获到事件去判断是否需要拦截事件，如果不需要拦截事件，就去遍历子view，倒着遍历然后循环的判断当前的点击区域是否包含当前的view，包含就会执行view的dispatchTouchEvent进行View的事件分发mMotionTarget就是childen的赋值
- up的时候ViewGroup捕获到事件去判断需不需要拦截事件，然后清空标记，调用view的dispatchTouchEvent进行View的事件分发
- movew的时候ViewGroup捕获到事件，然后判断是否拦截，如果没有拦截，则直接调用mMotionTarget.dispatchTouchEvent(ev)
- 分发之前的坐标都会经过修正之后传递给View当前的x，y分别减去child.left 和 child.top
- 就是为什么ViewGrou的onTouchEvent不会执行因为button设置了Ontouch，他一定会返回true，所以在dispatchTouchEvent就不会调用onTouchEvent
关于拦截事件
- 如果你需要拦截，只要return true就行了，这要该事件就不会往子View传递了，并且如果你在DOWN retrun true ，则DOWN,MOVE,UP子View都不会捕获事件；如果你在MOVE return true , 则子View在MOVE和UP都不会捕获事件。
- 原因很简单，当onInterceptTouchEvent(ev) return true的时候，会把mMotionTarget 置为null ;
