Broadcast Receiver详解
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Broadcast Receiver用于接收并处理广播通知(broadcastannouncements)。多数的广播是系统发起的,如地域变换、电量不足、来电来信等。程序也可以播放一个广播。程序可以有任意数量的broadcast receivers来响应它觉得重要的通知。broadcastreceiver可以通过多种方式通知用户:启动activity、使用NotificationManager、开启背景灯、振动设备、播放声音等,最典型的是在状态栏显示一个图标,这样用户就可以点它打开看通知内容。
通常我们的某个应用或系统本身在某些事件(电池电量不足、来电来短信)来临时会广播一个Intent出去,我们可以利用注册一个BroadcastReceiver来监听到这些Intent并获取Intent中的数据。
1. 我们自己的程序主动广播Intent
2.接收广播
接收broadcast需要注册一个Broadcast Receiver,并且要注册一个IntentFilter来制定BroadcaseReceiver是对哪些Intent进行监听。
(1)注册Broadcast Receiver
一个Broadcast receiver只有一个简单的回调函数:onReceive(Context curContext,IntentbroadcastMsg),当一个广播消息被Receiver监听到时,Android会调用它的onReceive()方法,并将包含消息的Intent对象传给它。onReceive中代码的执行时间不要超过5s,否则android会弹出超时dialog。此时是否另开一个线程来处理耗时的操作呢?
Receiver只在onReceive方法执行时是激活状态,只要onReceive一返回,Receiver就不再是激活状态了。Receiver进程是被一个激活状态的broadcastreceiver所保护而不被系统终止的,一旦onReceive返回,Receiver进程broadcastreceiver所保护而变为一个空进程,空进程是可以在任意时刻被终止的。这就带来了一个问题:当响应一个广播信息的处理十分耗时的时候,那么就应该把这个处理放在一个单独的线程里去执行,来保证主线程里的其他用户交互组件能够继续运行,而一旦这么做,当onReceive()唤起一个线程后就会马上返回,这时就会把Receiver进程放到被终止的境地。解决这个问题的方案是在onReceive()里开始一个Service,让这个Service去做这件事情,那么系统就会认为这个进程里还有活动正在进行。
(2)注册/注销Broadcast Receiver
1)在AndroidManifest.xml中注册
2)在代码中注册
3)注销
3. 示例代码
注册Broadcast Reciver
通常我们的某个应用或系统本身在某些事件(电池电量不足、来电来短信)来临时会广播一个Intent出去,我们可以利用注册一个BroadcastReceiver来监听到这些Intent并获取Intent中的数据。
1. 我们自己的程序主动广播Intent
Java代码
- final
String BROADCAST = "com.forrest.action.mybroadcast"; - Intent
intent = new Intent(BROADCAST); // 对应setAction() - intent.putExtra("data_title",
"来短信啦"); - intent.putExtra("data_text",
"美女你好,晚上可有空"); - sendBroadcast(intent);
2.接收广播
接收broadcast需要注册一个Broadcast Receiver,并且要注册一个IntentFilter来制定BroadcaseReceiver是对哪些Intent进行监听。
(1)注册Broadcast Receiver
一个Broadcast receiver只有一个简单的回调函数:onReceive(Context curContext,IntentbroadcastMsg),当一个广播消息被Receiver监听到时,Android会调用它的onReceive()方法,并将包含消息的Intent对象传给它。onReceive中代码的执行时间不要超过5s,否则android会弹出超时dialog。此时是否另开一个线程来处理耗时的操作呢?
Receiver只在onReceive方法执行时是激活状态,只要onReceive一返回,Receiver就不再是激活状态了。Receiver进程是被一个激活状态的broadcastreceiver所保护而不被系统终止的,一旦onReceive返回,Receiver进程broadcastreceiver所保护而变为一个空进程,空进程是可以在任意时刻被终止的。这就带来了一个问题:当响应一个广播信息的处理十分耗时的时候,那么就应该把这个处理放在一个单独的线程里去执行,来保证主线程里的其他用户交互组件能够继续运行,而一旦这么做,当onReceive()唤起一个线程后就会马上返回,这时就会把Receiver进程放到被终止的境地。解决这个问题的方案是在onReceive()里开始一个Service,让这个Service去做这件事情,那么系统就会认为这个进程里还有活动正在进行。
(2)注册/注销Broadcast Receiver
1)在AndroidManifest.xml中注册
Xml代码
- <</span>receiver
android:name="Receiver1"> -
<</span>intent-filter> -
-
<</span>action android:name="com.forrest.action.mybroadcast"/> -
</</span>intent-filter> - </</span>receiver>
2)在代码中注册
Java代码
- IntentFilter
filter = new IntentFilter("com.forrest.action.mybroadcast"); // 和广播中Intent的action对应 - MyBroadcastReceiver
br = new MyBroadcastReceiver(); - registerReceiver(new
MyBroadcastReceiver(), filter);
3)注销
Java代码
- unregisterReceiver(br);
3. 示例代码
Java代码
- public
class Receiver1 extends BroadcastReceiver { -
private Context context; -
public static final int NOTIFICATION_ID = 10001; -
-
public void onReceive(Context context, Intent intent) { -
this.context = context; -
showNotification(); -
} -
-
private void showNotification() { -
Notification notification = new Notification(R.drawable.icon, "来电话啦...", System.currentTimeMillis()); -
PendingIntent contentIntent = PendingIntent.getActivity(context, 0, new Intent(context, MainActivity.class), 0); -
notification.setLatestEventInfo(context, "来电话啦...嘿嘿", "赶紧接电话,否则误大事了", contentIntent); -
-
NotificationManager notificationManager = (NotificationManager) context.getSystemService( -
android.content.Context.NOTIFICATION_SERVICE); -
notificationManager.notify(NOTIFICATION_ID, notification); -
} - }
Java代码
- public
class Receiver2 extends BroadcastReceiver { -
private Context context; -
-
@Override -
public void onReceive(Context context, Intent intent) { -
this.context = context; -
deleteNotification(); -
} -
-
private void deleteNotification() { -
NotificationManager notificationManager = (NotificationManager) context.getSystemService(android.content.Context.NOTIFICATION_SERVICE); -
notificationManager.cancel(Receiver1.NOTIFICATION_ID); -
} - }
Java代码
- public
class MainActivity extends Activity { -
private final String ACTION_SEND = "com.forrest.action.SENDMESSAGE", -
ACTION_CLEAR = "com.forrest.action.CLEARNOTIFICATION"; -
-
public void onCreate(Bundle savedInstanceState) { -
super.onCreate(savedInstanceState); -
setContentView(R.layout.main); -
( (Button) findViewById(R.id.btn1) ).setOnClickListener(new OnClickListener() { -
public void onClick(View v) { -
clickMenuItem(ACTION_SEND); -
} -
}); -
( (Button) findViewById(R.id.btn2) ).setOnClickListener(new OnClickListener() { -
public void onClick(View v) { -
clickMenuItem(ACTION_CLEAR); -
} -
}); -
} -
-
private void clickMenuItem(final String action) { -
Intent intent = new Intent(action); -
sendBroadcast(intent); -
} - }
注册Broadcast Reciver
Xml代码
- <</span>application
android:icon="@drawable/icon" android:label="@string/app_name"> -
<</span>activity android:name=".MainActivity" -
android:label="@string/app_name"> -
<</span>intent-filter> -
<</span>action android:name="android.intent.action.MAIN" /> -
<</span>category android:name="android.intent.category.LAUNCHER" /> -
</</span>intent-filter> -
</</span>activity> -
<</span>receiver android:name="Receiver1"> -
<</span>intent-filter> -
<</span>action android:name="com.forrest.action.SENDMESSAGE"/> -
</</span>intent-filter> -
</</span>receiver> -
<</span>receiver android:name="Receiver2"> -
<</span>intent-filter> -
<</span>action android:name="com.forrest.action.CLEARNOTIFICATION"/> -
</</span>intent-filter> -
</</span>receiver> - </</span>application>
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