android 事件分发机制 _事件分发

愿君学长松，慎勿作桃李。这篇文章主要讲述android 事件分发机制相关的知识，希望能为你提供帮助。

文章图片

文章图片

我们通过代码来分析

package im.weiyuan.com.viewutils; import android.content.Intent; import android.os.PersistableBundle; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.util.Log; import android.view.MotionEvent; import android.view.View; import android.widget.Button; import android.widget.TextView; import android.widget.Toast; public class MainActivity extends AppCompatActivity {private MyView view; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); view = (MyView) findViewById(R.id.view_main); /** * 设置touch监听事件 * */ view.setOnTouchListener(new View.OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) {
Log.d("123456","MyView setOnTouchListener is called "); return false; } }); }@Override public boolean dispatchTouchEvent(MotionEvent ev) { Log.d("123456","activity dispatchTouchEvent is called" +ev.getAction()); return super.dispatchTouchEvent(ev); }@Override public boolean onTouchEvent(MotionEvent event) { Log.d("123456","activity onTouchEventis called"+event.getAction()); return super.onTouchEvent(event); } }

package im.weiyuan.com.viewutils; import android.content.Context; import android.util.AttributeSet; import android.util.Log; import android.view.MotionEvent; import android.view.View; import android.widget.ImageView; /** * Created by wei.yuan on 2017/7/24. */public class MyViewextends ImageView { public MyView(Context context) { super(context); }public MyView(Context context, AttributeSet attrs) { super(context, attrs); }public MyView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); }public MyView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) { super(context, attrs, defStyleAttr, defStyleRes); }@Override public boolean dispatchTouchEvent(MotionEvent event) { Log.d("123456","MyView dispatchTouchEvent is called"+event.getAction()); return super.dispatchTouchEvent(event); }@Override public boolean onTouchEvent(MotionEvent event) { Log.d("123456","MyView onTouchEvent is called"+event.getAction()); return super.onTouchEvent(event); } }

< ?xml version="1.0" encoding="utf-8"?> < LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context="im.weiyuan.com.viewutils.MainActivity"> < im.weiyuan.com.viewutils.MyView android:text="点击" android:src="https://www.songbingjia.com/android/@mipmap/ic_launcher" android:id="@+id/view_main" android:layout_width="100dp" android:layout_height="100dp" /> < /LinearLayout>

我们来进行下面的测试环境的操作：
1、点击activity的页面，不点击图片，只点击activity

07-24 11:29:59.882 16649-16649/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called0
07-24 11:29:59.882 16649-16649/im.weiyuan.com.viewutils D/123456: activity onTouchEventis called0
07-24 11:29:59.889 16649-16649/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called2
07-24 11:29:59.889 16649-16649/im.weiyuan.com.viewutils D/123456: activity onTouchEventis called2
07-24 11:29:59.911 16649-16649/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called2
07-24 11:29:59.911 16649-16649/im.weiyuan.com.viewutils D/123456: activity onTouchEventis called2
07-24 11:29:59.930 16649-16649/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called2
07-24 11:29:59.930 16649-16649/im.weiyuan.com.viewutils D/123456: activity onTouchEventis called2
07-24 11:29:59.937 16649-16649/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called2
07-24 11:29:59.938 16649-16649/im.weiyuan.com.viewutils D/123456: activity onTouchEventis called2
07-24 11:29:59.938 16649-16649/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called1
07-24 11:29:59.938 16649-16649/im.weiyuan.com.viewutils D/123456: activity onTouchEventis called1
日志的打印上面所示：
首先调用activity dispatchTouchEvent is called0 0表示手指按下 2表示手指移动，1表示手指抬起
dispatchTouchEvent会调用对应的activity的dispatchTouchEvent来分发事件
onTouchEvent 用来处理分发的事件
2、下面我们来进行下面的操作，我们点击图片，我们来看看日志打印

07-24 11:39:22.171 28610-28610/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called0
07-24 11:39:22.172 28610-28610/im.weiyuan.com.viewutils D/123456: MyView dispatchTouchEvent is called0
07-24 11:39:22.172 28610-28610/im.weiyuan.com.viewutils D/123456: MyView setOnTouchListener is called
07-24 11:39:22.173 28610-28610/im.weiyuan.com.viewutils D/123456: MyView onTouchEvent is called0
07-24 11:39:22.174 28610-28610/im.weiyuan.com.viewutils D/123456: activity onTouchEventis called0
07-24 11:39:22.185 28610-28610/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called2
07-24 11:39:22.185 28610-28610/im.weiyuan.com.viewutils D/123456: activity onTouchEventis called2
07-24 11:39:22.220 28610-28610/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called2
07-24 11:39:22.220 28610-28610/im.weiyuan.com.viewutils D/123456: activity onTouchEventis called2
07-24 11:39:22.228 28610-28610/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called2
07-24 11:39:22.228 28610-28610/im.weiyuan.com.viewutils D/123456: activity onTouchEventis called2
07-24 11:39:22.229 28610-28610/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called1
07-24 11:39:22.229 28610-28610/im.weiyuan.com.viewutils D/123456: activity onTouchEventis called1
首先是activity去分发事件，将事件分发给图片，图片没有孩子，不会再继续分发事件，这个时候取调用图片的回调方法TouchListen，然后调用MyView onTouchEvent去消费事件，
因为MyView onTouchEvent函数的返回值不是true，没有消费给事件，如果返回值是true，事件就被消费了，事件必须要有消费者，所以只能又把事件让给activity去处理，所以接下来调用了activity的: activity onTouchEvent is called0

后面调用了activity的 2 就是move事件，这里默认事件不再分发给图片处理了，为啥了，因为分发给图片的down 事件都没有消费，所以move事件就不会在分发给图片处理了
我们来验证下，我们把代码返回值设置成true

package im.weiyuan.com.viewutils; import android.content.Context; import android.util.AttributeSet; import android.util.Log; import android.view.MotionEvent; import android.view.View; import android.widget.ImageView; /** * Created by wei.yuan on 2017/7/24. */public class MyViewextends ImageView { public MyView(Context context) { super(context); }public MyView(Context context, AttributeSet attrs) { super(context, attrs); }public MyView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); }public MyView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) { super(context, attrs, defStyleAttr, defStyleRes); }@Override public boolean dispatchTouchEvent(MotionEvent event) { Log.d("123456","MyView dispatchTouchEvent is called"+event.getAction()); return super.dispatchTouchEvent(event); }@Override public boolean onTouchEvent(MotionEvent event) { Log.d("123456","MyView onTouchEvent is called"+event.getAction()); return true; } }

07-24 11:47:41.893 2667-2667/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called0
07-24 11:47:41.894 2667-2667/im.weiyuan.com.viewutils D/123456: MyView dispatchTouchEvent is called0
07-24 11:47:41.894 2667-2667/im.weiyuan.com.viewutils D/123456: MyView setOnTouchListener is called
07-24 11:47:41.895 2667-2667/im.weiyuan.com.viewutils D/123456: MyView onTouchEvent is called0
07-24 11:47:41.919 2667-2667/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called2
07-24 11:47:41.919 2667-2667/im.weiyuan.com.viewutils D/123456: MyView dispatchTouchEvent is called2
07-24 11:47:41.919 2667-2667/im.weiyuan.com.viewutils D/123456: MyView setOnTouchListener is called
07-24 11:47:41.919 2667-2667/im.weiyuan.com.viewutils D/123456: MyView onTouchEvent is called2
07-24 11:47:41.925 2667-2667/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called1
07-24 11:47:41.926 2667-2667/im.weiyuan.com.viewutils D/123456: MyView dispatchTouchEvent is called1
07-24 11:47:41.926 2667-2667/im.weiyuan.com.viewutils D/123456: MyView setOnTouchListener is called
07-24 11:47:41.926 2667-2667/im.weiyuan.com.viewutils D/123456: MyView onTouchEvent is called1
activity将时间分发给图片去处理，不管是down事件还是move事件，消费者都是图片
接下来做下面的事情，将图片的touch回调事件的返回值设置成true

package im.weiyuan.com.viewutils; import android.content.Intent; import android.os.PersistableBundle; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.util.Log; import android.view.MotionEvent; import android.view.View; import android.widget.Button; import android.widget.TextView; import android.widget.Toast; public class MainActivity extends AppCompatActivity {private MyView view; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); view = (MyView) findViewById(R.id.view_main); /** * 设置touch监听事件 * */ view.setOnTouchListener(new View.OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { Log.d("123456","MyView setOnTouchListener is called "); return true; } }); }@Override public boolean dispatchTouchEvent(MotionEvent ev) { Log.d("123456","activity dispatchTouchEvent is called" +ev.getAction()); return super.dispatchTouchEvent(ev); }@Override public boolean onTouchEvent(MotionEvent event) { Log.d("123456","activity onTouchEventis called"+event.getAction()); return super.onTouchEvent(event); } }

package im.weiyuan.com.viewutils; import android.content.Context; import android.util.AttributeSet; import android.util.Log; import android.view.MotionEvent; import android.view.View; import android.widget.ImageView; /** * Created by wei.yuan on 2017/7/24. */public class MyViewextends ImageView { public MyView(Context context) { super(context); }public MyView(Context context, AttributeSet attrs) { super(context, attrs); }public MyView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); }public MyView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) { super(context, attrs, defStyleAttr, defStyleRes); }@Override public boolean dispatchTouchEvent(MotionEvent event) { Log.d("123456","MyView dispatchTouchEvent is called"+event.getAction()); return super.dispatchTouchEvent(event); }@Override public boolean onTouchEvent(MotionEvent event) { Log.d("123456","MyView onTouchEvent is called"+event.getAction()); return true; } }

我们来看下日志的打印：

07-24 11:51:23.555 9263-9263/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called0
07-24 11:51:23.556 9263-9263/im.weiyuan.com.viewutils D/123456: MyView dispatchTouchEvent is called0
07-24 11:51:23.556 9263-9263/im.weiyuan.com.viewutils D/123456: MyView setOnTouchListener is called
07-24 11:51:23.591 9263-9263/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called2
07-24 11:51:23.591 9263-9263/im.weiyuan.com.viewutils D/123456: MyView dispatchTouchEvent is called2
07-24 11:51:23.591 9263-9263/im.weiyuan.com.viewutils D/123456: MyView setOnTouchListener is called
07-24 11:51:23.592 9263-9263/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called1
07-24 11:51:23.592 9263-9263/im.weiyuan.com.viewutils D/123456: MyView dispatchTouchEvent is called1
07-24 11:51:23.592 9263-9263/im.weiyuan.com.viewutils D/123456: MyView setOnTouchListener is called

我们来分析下，这个时候activity将事件分发给图片，因为图片的回调函数返回值是true，默认是回调函数对事件进行了消费了，所以这个时候就不会在调用图片的onTouchEvent消费事件了，事件的消费都有回调函数来进行处理了，一个事件只能被消费一次，
如果事件不被视图消费，最终由activity消费
我们来在做下面的修改

package im.weiyuan.com.viewutils; import android.content.Intent; import android.os.PersistableBundle; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.util.Log; import android.view.MotionEvent; import android.view.View; import android.widget.Button; import android.widget.TextView; import android.widget.Toast; public class MainActivity extends AppCompatActivity {private MyView view; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); view = (MyView) findViewById(R.id.view_main); /** * 设置touch监听事件 * */ view.setOnTouchListener(new View.OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { Log.d("123456","MyView setOnTouchListener is called "); if(event.getAction() == MotionEvent.ACTION_DOWN){ returntrue; } return false; } }); }@Override public boolean dispatchTouchEvent(MotionEvent ev) { Log.d("123456","activity dispatchTouchEvent is called" +ev.getAction()); return super.dispatchTouchEvent(ev); }@Override public boolean onTouchEvent(MotionEvent event) { Log.d("123456","activity onTouchEventis called"+event.getAction()); return super.onTouchEvent(event); } }

package im.weiyuan.com.viewutils; import android.content.Context; import android.util.AttributeSet; import android.util.Log; import android.view.MotionEvent; import android.view.View; import android.widget.ImageView; /** * Created by wei.yuan on 2017/7/24. */public class MyViewextends ImageView { public MyView(Context context) { super(context); }public MyView(Context context, AttributeSet attrs) { super(context, attrs); }public MyView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); }public MyView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) { super(context, attrs, defStyleAttr, defStyleRes); }@Override public boolean dispatchTouchEvent(MotionEvent event) { Log.d("123456","MyView dispatchTouchEvent is called"+event.getAction()); return super.dispatchTouchEvent(event); }@Override public boolean onTouchEvent(MotionEvent event) { Log.d("123456","MyView onTouchEvent is called"+event.getAction()); return true; } }

我们来看看日志的打印：

07-24 11:58:28.653 16280-16280/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called0
07-24 11:58:28.654 16280-16280/im.weiyuan.com.viewutils D/123456: MyView dispatchTouchEvent is called0
07-24 11:58:28.654 16280-16280/im.weiyuan.com.viewutils D/123456: MyView setOnTouchListener is called
07-24 11:58:28.657 16280-16280/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called2
07-24 11:58:28.657 16280-16280/im.weiyuan.com.viewutils D/123456: MyView dispatchTouchEvent is called2
07-24 11:58:28.658 16280-16280/im.weiyuan.com.viewutils D/123456: MyView setOnTouchListener is called
07-24 11:58:28.658 16280-16280/im.weiyuan.com.viewutils D/123456: MyView onTouchEvent is called2
07-24 11:58:28.674 16280-16280/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called2
07-24 11:58:28.674 16280-16280/im.weiyuan.com.viewutils D/123456: MyView dispatchTouchEvent is called2
07-24 11:58:28.674 16280-16280/im.weiyuan.com.viewutils D/123456: MyView setOnTouchListener is called
07-24 11:58:28.674 16280-16280/im.weiyuan.com.viewutils D/123456: MyView onTouchEvent is called2
07-24 11:58:28.690 16280-16280/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called2
07-24 11:58:28.691 16280-16280/im.weiyuan.com.viewutils D/123456: MyView dispatchTouchEvent is called2
07-24 11:58:28.691 16280-16280/im.weiyuan.com.viewutils D/123456: MyView setOnTouchListener is called
07-24 11:58:28.691 16280-16280/im.weiyuan.com.viewutils D/123456: MyView onTouchEvent is called2
07-24 11:58:28.757 16280-16280/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called2
07-24 11:58:28.758 16280-16280/im.weiyuan.com.viewutils D/123456: MyView dispatchTouchEvent is called2
07-24 11:58:28.758 16280-16280/im.weiyuan.com.viewutils D/123456: MyView setOnTouchListener is called
07-24 11:58:28.758 16280-16280/im.weiyuan.com.viewutils D/123456: MyView onTouchEvent is called2
07-24 11:58:28.758 16280-16280/im.weiyuan.com.viewutils D/123456: activity dispatchTouchEvent is called1
07-24 11:58:28.758 16280-16280/im.weiyuan.com.viewutils D/123456: MyView dispatchTouchEvent is called1
07-24 11:58:28.758 16280-16280/im.weiyuan.com.viewutils D/123456: MyView setOnTouchListener is called
07-24 11:58:28.758 16280-16280/im.weiyuan.com.viewutils D/123456: MyView onTouchEvent is called1