当设备失去网络连接时如何接收通知？

Question

我知道您可以编写代码来确定设备是否连接到网络。

但在我的应用程序中，我想做的是在设备将其状态从“网络”更改为“无网络”时收到通知。例如，当用户进入隧道并失去信号等时，会发生这种情况。或者在使用 WiFi 时，用户超出接入点的范围，不再能够访问互联网。

Android API 是否提供了可以注册侦听器的功能，以便在每次网络状态发生变化时收到通知？

我找到了这段代码并尝试使用它，但它什么也没做。当网络状态发生变化时，我没有收到任何通知。

public class ConnectivityManager extends PhoneStateListener{

Activity activity;
public ConnectivityManager(Activity a){
    TelephonyManager telephonyManager = (TelephonyManager)a.getSystemService(Context.TELEPHONY_SERVICE);
    telephonyManager.listen(this, PhoneStateListener.LISTEN_DATA_CONNECTION_STATE);
    activity = a;
}

@Override
public void onDataConnectionStateChanged(int state) {
    super.onDataConnectionStateChanged(state);
    switch (state) {
    case TelephonyManager.DATA_DISCONNECTED:
        new AlertDialog.Builder(activity).
        setCancelable(false).
        setTitle("Connection Manager").
        setMessage("There is no network connection. Please connect to internet and start again.").
        setNeutralButton("Ok", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int whichButton) {
                System.exit(0);
            }
        }).create();
        break;

    case TelephonyManager.DATA_CONNECTED:
        break;
    }
}
}

另外，我在 AndroidManifest.xml 中添加了相应的权限：

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

Answer 1

您可能需要考虑使用BroadcastReceiver 代替ConnectivityManager.CONNECTIVITY_ACTION。来自文档：

网络连接发生了变化。连接已建立或丢失。受影响网络的 NetworkInfo 作为额外发送；应该咨询它以了解发生了什么样的连接事件。

此接收器适用于 WiFi 和蜂窝数据连接，与 PhoneStateListener.LISTEN_DATA_CONNECTION_STATE 不同，后者只会在蜂窝网络发生变化时通知您。

Answer 2

myTelephonyManager=(TelephonyManager)getSystemService(Context.TELEPHONY_SERVICE);

callStateListener = new PhoneStateListener(){
    public void onDataConnectionStateChanged(int state){
        switch(state){
        case TelephonyManager.DATA_DISCONNECTED:
            Log.i("State: ", "Offline");
            // String stateString = "Offline";
            // Toast.makeText(getApplicationContext(),
            // stateString, Toast.LENGTH_LONG).show();
            break;
        case TelephonyManager.DATA_SUSPENDED:
            Log.i("State: ", "IDLE");
            // stateString = "Idle";
            // Toast.makeText(getApplicationContext(),
            // stateString, Toast.LENGTH_LONG).show();
            break;
        }
    }       
};                      
myTelephonyManager.listen(callStateListener,
            PhoneStateListener.LISTEN_DATA_CONNECTION_STATE); 

Answer 3

接受的答案对我不起作用（我的平板电脑已连接到 WiFi - 没有 3G）。以下代码对我有用：

public class ConnectivityChangeReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        System.out.println("*** Action: " + intent.getAction());
        if(intent.getAction().equalsIgnoreCase("android.net.conn.CONNECTIVITY_CHANGE")) {
            Toast.makeText(context, "Connection changed", Toast.LENGTH_SHORT).show();
        }
    }
}

以及对 AndroidManifest.xml 的更改

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

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

Answer 4

不确定这是否会有所帮助，但this looks similar...

Answer 5

我通过轮询 ConnectivityManager 实现了这个功能。

_connectivityManager = (ConnectivityManager)getSystemService(CONNECTIVITY_SERVICE);

一旦我们有了连接管理器，只需不时轮询它，看看您是否仍然连接

private final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
final Runnable networkStatusChecker = new Runnable() {
    public void run() {
        NetworkInfo activeNetwork = _connectivityManager.getActiveNetworkInfo();
        boolean isConnected = activeNetwork != null && activeNetwork.isConnectedOrConnecting();
        if(!isConnected) {
            System.out.println("disconnected from network");
            networkCheckerHandle.cancel(true);
        }
    }
};
final ScheduledFuture networkCheckerHandle = scheduler.scheduleAtFixedRate(networkStatusChecker, 10, 10, SECONDS);

Answer 6

如果你想在 Kotlin 中这样做。使用这个

   val isInternetWorking: Boolean by lazy {
        var success = false
        try {
            val url = URL("https://google.com")
            val connection = url.openConnection() as HttpURLConnection
            connection.connectTimeout = 10000
            connection.connect()
            success = connection.responseCode === 200
        } catch (e: IOException) {
            e.printStackTrace()
        }

        return@lazy success
    }

在一个线程中执行此操作。

Answer 7

您可以轻松使用 Merlin 和他的胡须。在这里您还可以获得一种连接类型：移动或 wifi。

implementation 'com.novoda:merlin:1.2.0'

private MerlinsBeard merlinsBeard;

private NetworkChecker(Context context){

    Merlin merlin = new Merlin.Builder()
            .withConnectableCallbacks()
            .withDisconnectableCallbacks()
            .build(context);

    merlinsBeard = new MerlinsBeard.Builder().build(context);

    merlin.registerConnectable(() -> {
        Timber.d("Connection enabled");
    });

    merlin.registerDisconnectable(() -> {
        Timber.d("Connection disabled");
    });

    merlin.bind();
}


public boolean getConnected(){
    return merlinsBeard.isConnected();
}