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

public class MainActivity extends AppCompatActivity {

    private MyBroadcaseReceiver receiver;
@Override
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main
 
);
IntentFilter filter = new IntentFilter();
filter.addAction(ConnectivityManager.CONNECTIVITY_ACTION);
receiver = new MyBroadcaseReceiver();
        this.registerReceiver(receiver, filter);
}

    class MyBroadcaseReceiver extends BroadcastReceiver {

        @Override
public void onReceive(Context context, 
 
Intent intent) {
//            判斷當前傳過來的Action是否是哪裡的斷網Actiion
if (intent.getAction().equals(ConnectivityManager.CONNECTIVITY_ACTION)) {
                ConnectivityManager manager = (ConnectivityManager) getSystemService(Context
                        .CONNECTIVITY_SERVICE);
NetworkInfo info = manager.getActiveNetworkInfo();
 
//判斷有網路或無網路
if (info != null && info.isConnected()) {
                    //如果有網,判斷當前是否是WIFI或移動資料或者其他第三方網路(VPN等)
if (ConnectivityManager.TYPE_WIFI == info.getType()) {
                        Toast.makeText(context, "WIFI已連結,可以下載資料", Toast.LENGTH_SHORT).show();
} else if (ConnectivityManager.TYPE_MOBILE == info.getType()) {
                        Toast.makeText(context, "當前使用的是移動資料,請謹慎使用", Toast.LENGTH_SHORT).show();
} else {
                        Toast.makeText(context, "連結的第三方網路,請謹慎使用", Toast.LENGTH_SHORT).show();
}
                } else {//如果沒有網路彈出吐司,也可以彈出對話方塊
Toast.makeText(context, "當前沒有網路,請連結網路", Toast.LENGTH_SHORT).show();
}
            }
        }
    }
}