最近，遇到这样一个需求：

手机可以随时监听网络状态，如果网络状态发生变化要及时的更新 app 信息通知用户。

实现这个需求，有个较好的办法（个人认为，你一定有更好的办法，希望分享），分享给大家！

随时监听，需要实现一个 service 在后台监听网络状态，那麽如何接收到网络状态发生变化的信息呢？

恩，当然是 BroadcastReceiver.

该值详细描述如下：

public static final String CONNECTIVITY_ACTION

Since: API Level 1
A change in network connectivity has occurred.
A connection has either been established or lost.
The NetworkInfo for the affected network is sent as an extra;
it should be consulted to see what kind of connectivity event occurred.
If this is a connection that was the result of failing over from a disconnected network,
then the FAILOVER_CONNECTION boolean extra is set to true.
For a loss of connectivity,
if the connectivity manager is attempting to connect (or has already connected) to another network,
the NetworkInfo for the new network is also passed as an extra.
This lets any receivers of the broadcast know that they should not necessarily tell the user that no data traffic will be possible.
Instead, the reciever should expect another broadcast soon,
indicating either that the failover attempt succeeded (and so there is still overall data connectivity),
or that the failover attempt failed, meaning that all connectivity has been lost.
For a disconnect event, the boolean extra EXTRA_NO_CONNECTIVITY is set to true if there are no connected networks at all.
Constant Value: "android.net.conn.CONNECTIVITY_CHANGE"

这是 ConnectivityManager 类的一个常量。

ok，下面是实现的 demo ：

package mark.zhang;

import android.app.Service;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.IBinder;
import android.util.Log;

public class ListenNetStateService extends Service {
private ConnectivityManager connectivityManager;
private NetworkInfo info;

private BroadcastReceiver mReceiver = new BroadcastReceiver() {

@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (action.equals(ConnectivityManager.CONNECTIVITY_ACTION)) {
Log.d("mark", "网络状态已经改变");
connectivityManager = (ConnectivityManager)

getSystemService(Context.CONNECTIVITY_SERVICE);
info = connectivityManager.getActiveNetworkInfo();
if(info != null && info.isAvailable()) {
String name = info.getTypeName();
Log.d("mark", "当前网络名称：" + name);
} else {
Log.d("mark", "没有可用网络");
}
}
}
};

@Override
public IBinder onBind(Intent intent) {
return null;
}

@Override
public void onCreate() {
super.onCreate();
IntentFilter mFilter = new IntentFilter();
mFilter.addAction(ConnectivityManager.CONNECTIVITY_ACTION);
registerReceiver(mReceiver, mFilter);
}

@Override
public void onDestroy() {
super.onDestroy();
unregisterReceiver(mReceiver);
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
return super.onStartCommand(intent, flags, startId);
}
}

在 manifest 文件中需要加上一条权限：

回头再看看关于 CONNECTIVITY_ACTION 的介绍，从 api 中，我们还可以得到一个信息：