Android编程监听网络连接状态改变的方法

public class MyReceiver extends BroadcastReceiver {  @Override  public void onReceive(Context context, Intent intent) {    // TODO Auto-generated method stub    //Toast.makeText(context, intent.getAction(), 1).show();    ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);    NetworkInfo mobileInfo = manager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);    NetworkInfo wifiInfo = manager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);    NetworkInfo activeInfo = manager.getActiveNetworkInfo();    Toast.makeText(context, "mobile:"+mobileInfo.isConnected()+"/n"+"wifi:"+wifiInfo.isConnected()            +"/n"+"active:"+activeInfo.getTypeName(), 1).show();  } //如果无网络连接activeInfo为null}

<receiver android:name=".MyReceiver">  <intent-filter>    <action android:name="android.net.conn.CONNECTIVITY_CHANGE"/>  </intent-filter></receiver>