如何用 CONNECTIVITY_CHANGE 定义 Broadcastreceiver？

Question

我是 android 初学者，想声明一个对 CONNECTIVITY_CHANGE 做出反应的广播接收器。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 我调用 checkInternet。当我断开 Internet 时，会显示 "No Internet" 和 "Internet" 消息。当我连接到 Internet 时，消息 "No Internet" 和 "Internet" 会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

试试下面的例子：

实施：

public class NetworkReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        if (intent.getAction().equals(ConnectivityManager.CONNECTIVITY_ACTION)) {
            NetworkInfo networkInfo = intent.getParcelableExtra(ConnectivityManager.EXTRA_NETWORK_INFO);
            if (networkInfo != null && networkInfo.getDetailedState() == NetworkInfo.DetailedState.CONNECTED) {
                Log.d("Network status: ", "Connected");
            } else if (networkInfo != null && networkInfo.getDetailedState() == NetworkInfo.DetailedState.DISCONNECTED) {
                Log.d("Network status: ", "Not connected");
            }
        }
    }
}

在您的 AndroidMenifest 中添加接收器：

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

Answer 2

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

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

并将此 class 添加到您的 activity

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

Answer 3

创建一个将从 BroadcastReceiver 扩展的新 class。在这里，您定义连接更改的意图过滤器。我们还创建了一个新的私有方法来检索网络连接的当前状态。

public class ConnectivityChangedBroadcastReceiver extends BroadcastReceiver {

public static IntentFilter getIntentFilter() {
    IntentFilter intentFilter = new IntentFilter();
    intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
    return intentFilter;
}

@Override
public void onReceive(Context context, Intent intent) {
    if (isNetworkAvailable(context)) {
        // Network is available
    } else {
        // Network is not available
    }
}

private boolean isNetworkAvailable(Context context) {
    ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
    return activeNetworkInfo != null && activeNetworkInfo.isConnectedOrConnecting();
}}

现在像这样在 activity 或应用程序 class 中注册您的广播接收器。请注意，面向 Android 7.0（API 级别 24）及更高版本的应用如果在其清单中声明了广播接收器，则不会收到 CONNECTIVITY_ACTION 广播。如果应用程序使用 Context.registerReceiver() 注册其 BroadcastReceiver 并且该上下文仍然有效，则应用程序仍将接收 CONNECTIVITY_ACTION 广播。所以，如果你想以最新版本的 Android 为目标，那么请确保你在代码中注册了接收器而不是清单

ConnectivityChangedBroadcastReceiver connectivityChangedBroadcastReceiver;
connectivityChangedBroadcastReceiver = new ConnectivityChangedBroadcastReceiver();
registerReceiver(connectivityChangedBroadcastReceiver, ConnectivityChangedBroadcastReceiver.getIntentFilter());

Answer 4

如前所述，所有解决方案均有效，问题出在 VM 上。当我在我的电脑上断开互联网时，虚拟机仍然有物理连接，但只是无法通信。因此，在我的 PC

上断开连接或连接时，消息 "Not connected" "connected" 会按此顺序显示

如何用 CONNECTIVITY_CHANGE 定义 Broadcastreceiver？

how define Broadcastreceiver with CONNECTIVITY_CHANGE?

android

broadcastreceiver