android - 如何使用 CONNECTIVITY_CHANGE 定义 Broadcastreceiver？

Question

我是 android 初学者，想声明一个对 CONNECTIVITY_CHANGE 使用react的广播接收器。我尝试了以下方法:

private void checkInternet () {
    IntentFilter ifilter = new IntentFilter ("android.net.conn.CONNECTIVITY_CHANGE");
    broadcastreceiver = new BroadcastReceiver () {
        @Override
        public void onReceive (Context Context, Intent Intent) {
            ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService (getApplicationContext (). CONNECTIVITY_SERVICE);
            NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo ();
            if (networkInfo! = null && networkInfo.getState () == NetworkInfo.State.CONNECTED)
                Toast.makeText (getApplicationContext (), "Internet", Toast.LENGTH_SHORT) .show ();
            else
                Toast.makeText (getApplicationContext (), "No Internet", Toast.LENGTH_SHORT) .show ();
        }
    };
    this.registerReceiver (broadcastreceiver, ifilter);
}

在 Actitvity.onCreate 中，我调用 checkInternet。当我断开 Internet 连接时，会显示“No Internet”和“Internet”这两个消息。当我连接到 Internet 时，“No Internet”和“Internet”这两个消息以相同的顺序再次出现。有人可以告诉我为什么 Broadcastreceiver 启动 2 次并显示 2 个不同的状态 pro Start 吗？提前谢谢你

Answer 1

如果您只需要检查互联网连接，您可以使用以下方法。在你的 Activity 中

 @Override
 protected void onCreate(Bundle savedInstanceState){
       ConnectionStateMonitor connectionStateMonitor = new ConnectionStateMonitor();
    connectionStateMonitor.enable(this);
 }

并在你的 Activity 中添加这个类

public class ConnectionStateMonitor extends ConnectivityManager.NetworkCallback {

    final NetworkRequest networkRequest;

    public ConnectionStateMonitor() {
        networkRequest = new NetworkRequest.Builder().
                addTransportType(NetworkCapabilities.TRANSPORT_CELLULAR).addTransportType(NetworkCapabilities.TRANSPORT_WIFI).build();
    }

    public void enable(Context context) {
        ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        connectivityManager.registerNetworkCallback(networkRequest , this);
    }
    // Likewise, you can have a disable method that simply calls ConnectivityManager#unregisterCallback(networkRequest) too.

    @Override
    public void onAvailable(Network network) {
         //do what you want when Connection is available
    }
    @Override
    public void onLost(Network network){
        //Connection Lost
    }
}

我认为这比使用广播接收器更容易