广播的类型————拦截有序广播

 导语： 在Android系统中，根据广播的执行顺序不同，可将其分为有序广播和无序广播。有序广播是一种同步执行的广播，在广播发出之后，同一时刻只会有一个广播接收器能够接收到这条消息，当这个广播接收器中的逻辑执行完毕后，广播才会继续传递。所以，此时的广播接收器是有先后顺序的，并且可以被拦截。有序广播发送一条消息后，高优先级的广播接收器先接收到广播，低优先级的广播后接收到广播。想要拦截一条广播，可使用abortBroadcast();方法。

下面具体介绍如何实现拦截有序广播

1.用户交互界面的设计与实现

<?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:background="@drawable/stitch_one"
    tools:context="com.example.bz0209.orderedbroadcast.MainActivity">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="80dp"
        android:onClick="send"
        android:text="发送有序广播"
        android:paddingLeft="5dp"
        android:paddingRight="5dp"
        android:background="#FBFBFF"
        android:textSize="20sp"/>
</RelativeLayout>

2.界面交互代码的设计与实现

package com.example.bz0209.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();
        intent.setAction("Intercept_Switch");
        sendOrderedBroadcast(intent,null);
    }
}

3.创建三个广播接收者：

<1>MyBroadcastReceiverOne.java

package com.example.bz0209.orderedbroadcast;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
public class MyBroadcastReceiverOne extends BroadcastReceiver {
  @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>MyBroadcastReceiverTwo.java

package com.example.bz0209.orderedbroadcast;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
public class MyBroadcastReceiverTwo extends BroadcastReceiver {
    @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();//拦截有序广播
        Log.i("MyBroadcastReceiverTwo","我是接收者Two，广播被我终结了");
    }
}

<3>MyBroadcastReceiverThree.java

package com.example.bz0209.orderedbroadcast;

import android.annotation.SuppressLint;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
public class MyBroadcastReceiverThree extends BroadcastReceiver {
    @SuppressLint("LongLogTag")
    @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");

    }
}

4.设置优先级广播接收者的优先级

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.bz0209.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>
            <receiver android:name=".MyBroadcastReceiverOne">
            <intenf-filter android:priority="1000">
                <action android:name="Intercept_Stitch"/>
            </intenf-filter>
        </receiver>
            <receiver android:name=".MyBroadcastReceiverTwo">
                <intenf-filter android:priority="200">
                    <action android:name="Intercept_Stitch"/>
                </intenf-filter>
            </receiver>
            <receiver android:name=".MyBroadcastReceiverThree">
                <intenf-filter android:priority="600">
                    <action android:name="Intercept_Stitch"/>
                </intenf-filter>
            </receiver>
            <receiver
                android:name=".MyReceiver"
                android:enabled="true"
                android:exported="true">
                <intent-filter android:priority="100"/>
            </receiver>
        </activity>
    </application>

</manifest>
其中在清单文件中注册广播接收者<intent-filter android:priority="100"/>属性指定数值越大，优先级越高。如果两个广播接收者的优先级相同，则先注册的组件优先接收到广播。如果两个应用程序监听了同一个广播事件并设置了优先级，则先安装的应用优先接收到广播。

5.运行效果如下