Android系统提供了两种广播类型，一种是有序广播，一种是有序广播。
（1）无序广播是完全异步执行，发送广播时所有监听这个广播的广播接收者都会收到此消息，但接收的顺序不确定。
（2）有序广播是按照接收者的优先级接收，只有一个广播接收者能接收信息，在此广播接收者中逻辑执行完毕后，才会继续传递。
实验要求：通过sendOrderedBroadeast（）发送一条有序广播
1.在activity-main.xml布局文件中代码如下：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"
android:background="@drawable/stitch_one"
tools:context="cn.edu.bzu.orderedbroadcast.MainActivity">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:onClick="send"
android:layout_marginTop="50dp"
android:text="发送有序广播"
android:paddingLeft="5dp"
android:paddingRight="5dp"
android:background="#FFD202"
android:textSize="20sp"
/>
</RelativeLayout>
2.在MainActivity中代码如下：
package cn.edu.bzu.orderedbroadcast;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void send(View view){
Intent intent=new Intent();
//定义广播事件类型
intent.setAction("Intercept_Stitch");
//发送广播
sendOrderedBroadcast(intent,null);
}
}
（1）MyBroadcastReceiverOne
（2）MyBroadcastReceiverTwo
（3）MyBroadcastReceiverThree
（1）在MyBroadcastReceiverOne中代码如下:
package cn.edu.bzu.orderedbroadcast;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
public class MyBroadcastReceiverOne extends BroadcastReceiver {
public MyBroadcastReceiverOne() {
}
@Override
public void onReceive(Context context, Intent intent) {
Log.i("MyBroadcastReceiverOne","自定义的广播接收者one，接收到了广播事件");
}
}
（2）在MyBroadcastReceiverTwo中代码如下:
package cn.edu.bzu.orderedbroadcast;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
public class MyBroadcastReceiverTwo extends BroadcastReceiver {
public MyBroadcastReceiverTwo() {
}
@Override
public void onReceive(Context context, Intent intent) {
Log.i("MyBroadcastReceiverTwo","自定义的广播接收者Two，接收到了广播事件");
}
}
（3）在MyBroadcastReceiverThree中代码如下:
package cn.edu.bzu.orderedbroadcast;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
public class MyBroadcastReceiverThree extends BroadcastReceiver {
public MyBroadcastReceiverThree() {
}
@Override
public void onReceive(Context context, Intent intent) {
Log.i("MyBroadcastReceiverThree","自定义的广播接收者Three，接收到了广播事件");
}
}<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="cn.edu.bzu.orderedbroadcast">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<receiver
android:name=".MyBroadcastReceiverOne">
<intent-filter android:priority="1000">
<action android:name="Intercept_Stitch"/>
</intent-filter>
</receiver>
<receiver
android:name=".MyBroadcastReceiverTwo">
<intent-filter android:priority="200">
<action android:name="Intercept_Stitch"/>
</intent-filter>
</receiver>
<receiver
android:name=".MyBroadcastReceiverThree">
<intent-filter android:priority="600">
<action android:name="Intercept_Stitch"/>
</intent-filter>
</receiver>
</application>
</manifest>
运行程序后解决如下问题：
问题1：程序启动后，单击“发送有序广播”按钮，发出一条广播事件，此时观察LogCat窗口下的提示信息，输出什么？为什么？
点击按钮后出现如下图所示提示信息，原因是有序广播根据优先级接收广播信息的，在配置文件中广播接收者One的priority值最大，所以它先接收到广播，其次是Three，最后是Two。其中android:priority="值"是用来设置广播接收者的优先级的，值越大，优先级别越高。
问题2：若将广播接收者MyBroadcastReceiverTwo优先级同样设置为1000，并将MyBroadcastReceiverTwo注册在MyBroadcastReceiverOne前面，再来运行程序，观察结果，你能得出什么结论？
修改配置文件AndroidManifest中代码如下：
<receiver
android:name=".MyBroadcastReceiverTwo">
<intent-filter android:priority="1000">
<action android:name="Intercept_Stitch"/>
</intent-filter>
</receiver>
<receiver android:name=".MyBroadcastReceiverOne">
<intent-filter android:priority="1000">
<action android:name="Intercept_Stitch"/>
</intent-filter>
</receiver>
<receiver
android:name=".MyBroadcastReceiverThree">
<intent-filter android:priority="600">
<action android:name="Intercept_Stitch"/>
</intent-filter>
</receiver>
问题3：修改MyBroadcastReceiverTwo如下，观察结果，你又可以得出什么结论？
public class MyBroadcastReceiverTwo extends BroadcastReceiver {
public MyBroadcastReceiverTwo() {
}
@Override
public void onReceive(Context context, Intent intent) {
Log.i("MyBroadcastReceiverTwo","自定义的广播接收者Two，接收到了广播事件");
abortBroadcast();//有序广播拦截器
Log.i("MyBroadcastReceiverTwo","我是广播接收者Two,广播被我终止了");
}
}
