BroadcastReceiver
在Android中,Broadcast是一种广泛运用的在应用程序之间传输信息的机制。而BroadcastReceiver是对发送出来的 Broadcast进行过滤接受并响应的一类组件。
下面将详细的阐述如何发送Broadcast和使用BroadcastReceiver过滤接收的过程:
首先在需要发送信息的地方,把要发送的信息和用于过滤的信息(如Action、Category)装入一个Intent对象,然后通过调用 sendOrderBroadcast()或sendStickyBroadcast()方法,把 Intent对象以广播方式发送出去。
当Intent发送以后,所有已经注册的BroadcastReceiver会检查注册时的IntentFilter是否与发送的Intent相匹配,若匹配则就会调用BroadcastReceiver的onReceive()方法。所以当我们定义一个BroadcastReceiver的时候,都需要实现onReceive()方法。
注册BroadcastReceiver有两种方式:
静态注册:在AndroidManifest.xml中用标签生命注册,并在标签内用标签设置过滤器。
<receiver android:name="myRecevice"> //继承BroadcastReceiver,重写onReceiver方法
<intent-filter>
<action android:name="com.dragon.net"></action> //使用过滤器,接收指定action广播
</intent-filter>
</receiver>
动态注册:
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(String); //为BroadcastReceiver指定action,使之用于接收同action的广播
registerReceiver(BroadcastReceiver,intentFilter);
一般:在onStart中注册,onStop中取消unregisterReceiver
指定广播目标Action:Intent intent = new Intent(actionString);
并且可通过Intent携带消息 :intent.putExtra("msg", "hi,我通过广播发送消息了");
发送广播消息:Context.sendBroadcast(intent )
其中在动态注册中可将BroadcastReceiver的继承类进行封装,添加构造函数和BroadcastReceiver注册
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
public class BroadcastReceiverHelper extends BroadcastReceiver {
NotificationManager mn = null ;
Notification notification = null ;
Context ct = null ;
BroadcastReceiverHelper receiver;
public BroadcastReceiverHelper(Context c){
ct = c;
receiver = this ;
}
// 注册
public void registerAction(String action){
IntentFilter filter = new IntentFilter();
filter.addAction(action);
ct.registerReceiver(receiver, filter);
}
@Override
public void onReceive(Context context, Intent intent) {
// TODO Auto-generated method stub
String msg = intent.getStringExtra( " msg " );
int id = intent.getIntExtra( " who " , 0 );
if (intent.getAction().equals( " com.cbin.sendMsg " )){
mn = (NotificationManager)context.getSystemService(Context.NOTIFICATION_SERVICE);
notification = new Notification(R.drawable.icon, id + " 发送广播 " , System.currentTimeMillis());
Intent it = new Intent(context,Main. class );
PendingIntent contentIntent = PendingIntent.getActivity(context,
0 , it, 0 );
notification.setLatestEventInfo(context,
" msg " , msg, contentIntent);
mn.notify( 0 , notification);
}
}
}
然后再Activity中声明BroadcastReceiver的扩展对象,在onStart中注册,onStop中卸载
BroadcastReceiverHelper rhelper;
@Override
public void onStart(){
// 注册广播接收器
rhelper = new BroadcastReceiverHelper( this );
rhelper.registerAction( " com.cbin.sendMsg " );
super .onStart();
}
@Override
public void onStop(){
// 取消广播接收器
unregisterReceiver(rhelper);
super .onStop();
}