如何使用CONNECTIVITY_CHANGE定义Broadcastreceiver？

Posted 2021-04-09

我是android初学者，想要声明一个对CONNECTIVITY_CHANGE作出反应的broadcastreceiver。我尝试过以下方法：

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。当我断开互联网时，会显示“无互联网”和“互联网”两条消息。当我连接互联网时，“无互联网”和“互联网”这两条消息再次以相同的顺序出现。有人可以告诉我为什么Broadcastreceiver 2次启动并显示2个不同的状态亲开始？我提前谢谢你

答案

请尝试以下示例：

执行：

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AndroidManifest中添加接收器：

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

另一答案

如果您只需要检查互联网连接，可以使用以下内容。在你的活动中

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

并在您的活动中添加此类

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broadCast接收器更容易

另一答案

创建一个将从BroadcastReceiver扩展的新类。在此处定义连接更改的intent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();
}}

现在在活动或应用程序类中注册您的广播接收器。请注意，针对Android 7.0（API级别24）及更高版本的应用如果在其清单中声明广播接收器，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，则仍会收到CONNECTIVITY_ACTION广播。因此，如果您想要定位最新版本的Android，请确保在代码中注册接收器而不是显示

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

另一答案

如上所述，所有解决方案都有效，问题是VM。当我在计算机上断开Internet连接时，VM仍然具有物理连接，但只能进行通信。因此，在我的PC上断开连接或连接时，按此顺序显示消息“未连接”“已连接”