很簡單，所以直接看程式碼。

package xxx;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;

public class NetstateReceiver extends BroadcastReceiver {

	@Override
	public void onReceive(Context context, Intent intent) {
		ConnectivityManager manager = (ConnectivityManager) context
				.getSystemService(Context.CONNECTIVITY_SERVICE);
		NetworkInfo gprs = manager
				.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);
		NetworkInfo wifi = manager
				.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
		if (!gprs.isConnected() && !wifi.isConnected()) {
			// network closed
		} else {
			// network opend
 

		}
	}

}

程式碼自定義了一個BroadcastReceiver，是想監聽網路設定變化的事件。

Manifest檔案裡註冊監聽。

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

還需要加入許可權資訊。

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