Android：BroadcastReceiver

参考：《第一行代码：Android》 郭霖(著)

 

Broadcast分类

注册方式：

• 动态广播
  • 在代码中注册receiver
  • 一定要手动在onDestroy()时调用unregisterReveiver()来取消注册
• 静态广播
  • 在AndroidManifest.xml中注册receiver(主要是设定action)

动态广播：

1. 在代码中设置receiver、监听的广播类型并进行注册：

 public class MainActivity extends Activity {
     private NetworkChangeReceiver receiver;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);

         IntentFilter intentFilter = new IntentFilter();
         intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");

         receiver = new NetworkChangeReceiver();
         registerReceiver(receiver, intentFilter);
     }

     @Override
     protected void onDestroy() {
         unregisterReceiver(receiver);//remember to unregister manually
         super.onDestroy();
     }
 }

2. 定义receiver的行为：继承BroadcastReceiver并在覆写onReceiver()时定义好接收到广播时处理的逻辑：

 public class NetworkChangeReceiver extends BroadcastReceiver {
     @Override
     public void onReceive(Context context, Intent intent) {
         ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
         NetworkInfo networkInfo = manager.getActiveNetworkInfo();
         if(networkInfo != null && networkInfo.isAvailable())
             Toast.makeText(context, "Network is available.", Toast.LENGTH_SHORT).show();
         else
             Toast.makeText(context, "Network is unavailable.", Toast.LENGTH_SHORT).show();
     }
 }

3. 在AndroidManifest.xml中定义必要的权限，主要<uses-permission>标签位于<manifest>的下一级，即与<application>同级：

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

 

静态广播(以开机启动的广播为例)

1. 定义receiver的行为：

 public class BootCompleteReceiver extends BroadcastReceiver {
     @Override
     public void onReceive(Context context, Intent intent) {
         Toast.makeText(context, "Boot complete.", Toast.LENGTH_LONG).show();
     }
 }

2. 在AndroidManifest.xml中定义receiver(与<activity>同级，<application>的子元素)：

 <receiver android:name=".MyBroadcast">
     <intent-filter android:priority="100">
         <action android:name="com.scv.lawrence.MY_BROADCAST"/>
     </intent-filter>
 </receiver>

3. 在AndroidManifest.xml中添加相应权限(<application>同级，<manifest>的子元素)：

<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>

 

接收顺序：

• 标准(Normal broadcast)
  • 默认的广播方式，即broadcast发出后，所有receiver几乎在同时接收到。
• 有序(Ordered broadcast)
  • receiver根据设定的优先级(priority)来决定broadcast的传递顺序，较高优先级的receiver可以选择拦截该broadcast阻止其向后传播
• 二者区别
  • 发送广播时，标准广播调用的是sendBroadcast()，有序广播调用的是sendOrderedBroadcast()
  • 接收广播时(在AndroidManifest.xml中注册receiver)，标准广播不用在<intent-filter>中设置android:priority属性，有序广播则需要设定一个整数，数值越大priority越高

在代码中发送自定义的标准/无序广播：

 Button sendBroadcast = (Button) findViewById(R.id.broadcast);
 sendBroadcast.setOnClickListener(new View.OnClickListener() {
     @Override
     public void onClick(View v) {
         Intent intent = new Intent("com.scv.lawrence.MY_BROADCAST");
         sendBroadcast(intent);
 //      sendOrderedBroadcast(intent, null);
     }
 });

在AndroidManifest.xml中定义(父元素为<application>，即与<activity>同级)：

 <receiver android:name=".MyBroadcast">
     <intent-filter android:priority="100">
         <action android:name="com.scv.lawrence.MY_BROADCAST"/>
     </intent-filter>
 </receiver>

广播范围：

• 全局广播
  • 非LocalBroadcastManager进行发送或接收的广播即为全局广播
• 本地广播
  • 发送/接收的broadcast只限于当前app范围内，安全性比全局高
  • 与全局广播的区别在于本地广播依靠LocalBroadcastManager进行注册、发送及注销receiver

 本地广播：

1. 定义接收到广播的行为：

 public class LocalBroadcastReceiver extends BroadcastReceiver {
     @Override
     public void onReceive(Context context, Intent intent) {
         Toast.makeText(context, "Get the local broadcast.", Toast.LENGTH_SHORT).show();
     }
 }

2. 和动态广播差不多，区别主要在使用LocalBroadcastManager的实例来进行操作：

 public class MainActivity extends Activity {
     private LocalBroadcastManager localBroadcastManager;
     private LocalBroadcastReceiver localReceiver;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);

         //Local Broadcast
         localBroadcastManager = LocalBroadcastManager.getInstance(MainActivity.this);

         final Button localBroadcast = (Button) findViewById(R.id.local_broadcast);
         localBroadcast.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
                 Intent intent = new Intent("com.scv.lawrence.LOCAL_BROADCAST");
                 localBroadcastManager.sendBroadcast(intent);
             }
         });

         IntentFilter localIntentFilter = new IntentFilter();
         localIntentFilter.addAction("com.scv.lawrence.LOCAL_BROADCAST");

         localReceiver = new LocalBroadcastReceiver();
         localBroadcastManager.registerReceiver(localReceiver, localIntentFilter);
     }

     @Override
     protected void onDestroy() {
         localBroadcastManager.unregisterReceiver(localReceiver);
         super.onDestroy();
     }
 }

3. 在AndroidManifest.xml中配置permission. (如有必要)