Android的事件机制
栏目：综合技术时间：2016-11-11 08:31:08
Android的事件机制
1、理论概述
最基本的操作类型：
- down 手指按下
- move 手指在屏幕上移动
- up 手指从屏幕上离开
触屏操作的顺序：down->move->move->…->up
对屏幕的任1操作，系统都会产生1个MotionEvent对象来对应这个对象。
注：点击和长按可以同时满足，如果只想满足长按，则让长按的监听返回true。点击和长按时可以move。
2、相干API
1、MotionEvent：触发事件
- int ACTION_DOWN = 0 : 代表down
- int ACTION_MOVE = 2 : 代表move
- int ACTION_UP = 1 : 代表up
- getAction() : 得到事件类型
- getX() : 得到事件产生的X轴的坐标（相对当前视图）
- getRawX() : 得到事件产生的X轴的坐标（相对屏幕左顶点）
- getY() : 得到事件产生的Y轴的坐标（相对当前视图）
- getRawY() : 得到事件产生的Y轴的坐标（相对屏幕左顶点）
2、Activity
- boolean dispatchTouchEvent(MotionEvent event) : 分发事件
- boolean onTouchEvent(MotionEvent event) : 处理事件的回调（当没有子View消费时才调用该方法）
3、View
- boolean dispatchTouchEvent(MotionEvent event) : 分发事件（没有子view，用来决定是使用onTouchEvent还是setOnTouchListener）
- boolean onTouchEvent(MotionEvent event) : 处理事件的回调方法
- void setOnTouchListener(OnTouchListener listener) : 设置事件监听器
- void setOnClickListener(OnClickListener l)
- void setOnLongClickListener(OnClickListener l)
- void setOnCreateContextMenuListener(OnCreateContextMenuListener l) 用于创建菜单监听
4、ViewGroup
- boolean dispatchTouchEvent(MotionEvent event) : 分发事件
- boolean onInterceptTouchEvent(MotionEvent event) : 拦截事件的回调方法
注：这里引入两个概念：处理和消费
只要调用了方法就叫做处理了；
只有返回了true才叫消费了；
事件对象被系统创建后，首先会调用对应Activity的dispatchTouchEvent()进行分发；
down在分发给视图对象的进程中要肯定消费者（onTouchEvent()返回true），如果都返回false，那事件的消费者只能是activity了。
后面的move和up都将分发给消费者（多是视图对象，也多是消费者）
当前事件的消费者只是决定了下1个事件优先交给他处理
每一个事件都需要有1个消费者
例子：
MotionEventActivity.java
package com.cwenhui.motionevent;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import com.cwenhui.test.R;
/**
* Created by cwenhui on 2016.02.23
*/
public class MotionEventActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout_motionevent);
findViewById(R.id.myImageview).setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
Log.e("MotionEventActivity", "setOnTouchListener");
return false;
}
});
}
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
Log.e("MotionEventActivity", "dispatchTouchEvent--"+ev.getAction());
return super.dispatchTouchEvent(ev);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
Log.e("MotionEventActivity", "onTouchEvent--"+event.getAction());
return super.onTouchEvent(event);
}
}
layout_motionevent.xml:
<?xml version="1.0" encoding="utf⑻"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:orientation="vertical">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="motionEvent"/>
<com.cwenhui.motionevent.MyImageView
android:id="@+id/myImageview"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/test"/>
</LinearLayout>MyImageview.java
package com.cwenhui.motionevent;
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.widget.ImageView;
/**
* Created by cwenhui on 2016.02.23
*/
public class MyImageView extends ImageView {
public MyImageView(Context context) {
super(context);
}
public MyImageView(Context context, AttributeSet attrs) {
super(context, attrs);
Log.e("MyImageView", "MyImageView");
}
public MyImageView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
@Override
public boolean dispatchTouchEvent(MotionEvent event) {
Log.e("MyImageView", "dispatchTouchEvent--"+event.getAction());
return super.dispatchTouchEvent(event);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
Log.e("MyImageView", "onTouchEvent--"+event.getAction());
return super.onTouchEvent(event)/*true*/;
}
}
运行分析：
如果点击图片并滑动，则
09-20 03:20:37.674 25085-25085/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--0
09-20 03:20:37.674 25085-25085/com.cwenhui.test E/MyImageView: dispatchTouchEvent--0
09-20 03:20:37.674 25085-25085/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 03:20:37.674 25085-25085/com.cwenhui.test E/MyImageView: onTouchEvent--0
09-20 03:20:37.674 25085-25085/com.cwenhui.test E/MotionEventActivity: onTouchEvent--0
09-20 03:20:37.708 25085-25085/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:20:37.708 25085-25085/com.cwenhui.test E/MotionEventActivity: onTouchEvent--2
09-20 03:20:37.724 25085-25085/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:20:37.724 25085-25085/com.cwenhui.test E/MotionEventActivity: onTouchEvent--2
09-20 03:20:37.741 25085-25085/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:20:37.741 25085-25085/com.cwenhui.test E/MotionEventActivity: onTouchEvent--2
09-20 03:20:37.758 25085-25085/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:20:37.758 25085-25085/com.cwenhui.test E/MotionEventActivity: onTouchEvent--2
09-20 03:20:37.774 25085-25085/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:20:37.774 25085-25085/com.cwenhui.test E/MotionEventActivity: onTouchEvent--2
09-20 03:20:37.802 25085-25085/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--1
09-20 03:20:37.802 25085-25085/com.cwenhui.test E/MotionEventActivity: onTouchEvent--1
如果将MyImageview.java中的onTouchEvent(MotionEvent event)返回值改成true，则
09-20 03:22:16.122 2077-2077/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--0
09-20 03:22:16.122 2077-2077/com.cwenhui.test E/MyImageView: dispatchTouchEvent--0
09-20 03:22:16.122 2077-2077/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 03:22:16.122 2077-2077/com.cwenhui.test E/MyImageView: onTouchEvent--0
09-20 03:22:16.174 2077-2077/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:22:16.174 2077-2077/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 03:22:16.174 2077-2077/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 03:22:16.174 2077-2077/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 03:22:16.191 2077-2077/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:22:16.191 2077-2077/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 03:22:16.191 2077-2077/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 03:22:16.191 2077-2077/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 03:22:16.208 2077-2077/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:22:16.208 2077-2077/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 03:22:16.208 2077-2077/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 03:22:16.208 2077-2077/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 03:22:16.224 2077-2077/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:22:16.224 2077-2077/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 03:22:16.224 2077-2077/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 03:22:16.224 2077-2077/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 03:22:16.279 2077-2077/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--1
09-20 03:22:16.279 2077-2077/com.cwenhui.test E/MyImageView: dispatchTouchEvent--1
09-20 03:22:16.279 2077-2077/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 03:22:16.279 2077-2077/com.cwenhui.test E/MyImageView: onTouchEvent--1
如果此时MotionEventActivity中的OnTouchListener的onTouch()方法返回true，以下：
findViewById(R.id.myImageview).setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
Log.e("MotionEventActivity", "setOnTouchListener--"+event.getAction());
return true;
}
});运行结果以下：
09-20 15:01:53.068 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--0
09-20 15:01:53.068 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--0
09-20 15:01:53.068 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 15:01:53.105 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 15:01:53.105 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 15:01:53.105 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 15:01:53.122 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 15:01:53.122 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 15:01:53.122 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 15:01:53.138 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 15:01:53.139 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 15:01:53.139 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 15:01:53.155 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 15:01:53.155 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 15:01:53.155 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 15:01:53.172 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 15:01:53.172 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 15:01:53.172 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 15:01:53.189 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 15:01:53.189 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 15:01:53.189 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 15:01:53.237 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 15:01:53.237 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 15:01:53.237 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 15:01:53.237 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--1
09-20 15:01:53.237 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--1
09-20 15:01:53.237 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
可见，没有履行MyImageview的onTouchEvent(MotionEvent event)方法了。
如果改成手指按下时返回true，即
findViewById(R.id.myImageview).setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
Log.e("MotionEventActivity", "setOnTouchListener--"+event.getAction());
// return false;
if (event.getAction() == MotionEvent.ACTION_DOWN) {
return true;
}
return false;
}
});结果为:
09-20 16:30:48.573 16591-16591/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--0
09-20 16:30:48.573 16591-16591/com.cwenhui.test E/MyImageView: dispatchTouchEvent--0
09-20 16:30:48.573 16591-16591/com.cwenhui.test E/MotionEventActivity: setOnTouchListener--0
09-20 16:30:48.605 16591-16591/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 16:30:48.605 16591-16591/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 16:30:48.605 16591-16591/com.cwenhui.test E/MotionEventActivity: setOnTouchListener--2
09-20 16:30:48.605 16591-16591/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 16:30:48.622 16591-16591/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 16:30:48.622 16591-16591/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 16:30:48.622 16591-16591/com.cwenhui.test E/MotionEventActivity: setOnTouchListener--2
09-20 16:30:48.622 16591-16591/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 16:30:48.638 16591-16591/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 16:30:48.639 16591-16591/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 16:30:48.639 16591-16591/com.cwenhui.test E/MotionEventActivity: setOnTouchListener--2
09-20 16:30:48.639 16591-16591/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 16:30:48.655 16591-16591/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 16:30:48.655 16591-16591/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 16:30:48.655 16591-16591/com.cwenhui.test E/MotionEventActivity: setOnTouchListener--2
09-20 16:30:48.655 16591-16591/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 16:30:48.672 16591-16591/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 16:30:48.672 16591-16591/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 16:30:48.672 16591-16591/com.cwenhui.test E/MotionEventActivity: setOnTouchListener--2
09-20 16:30:48.672 16591-16591/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 16:30:48.689 16591-16591/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 16:30:48.689 16591-16591/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 16:30:48.689 16591-16591/com.cwenhui.test E/MotionEventActivity: setOnTouchListener--2
09-20 16:30:48.689 16591-16591/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 16:30:48.717 16591-16591/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--1
09-20 16:30:48.717 16591-16591/com.cwenhui.test E/MyImageView: dispatchTouchEvent--1
09-20 16:30:48.718 16591-16591/com.cwenhui.test E/MotionEventActivity: setOnTouchListener--1
09-20 16:30:48.718 16591-16591/com.cwenhui.test E/MyImageView: onTouchEvent--1
可见down的时候，事件对象是给OnTouchListener消费了；
move和up时，事件对象给OnTouch消费了。
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