NetworkCallback 监听回调 WiFi切换移动数据

当 Android 设备的 WiFi 连接不稳定或信号弱时，系统可能会自动切换到移动数据网络。您可以使用 NetworkCallback 监听回调来检测这种网络切换。

以下是一个简单的示例代码，用于监听网络连接状态的变化并在网络切换到移动数据时发送通知：

public class ConnectivityReceiver extends ConnectivityManager.NetworkCallback {
    private Context mContext;
    private NotificationManager mNotificationManager;
    private static final int NOTIFICATION_ID = 123;

    public ConnectivityReceiver(Context context) {
        mContext = context;
        mNotificationManager = (NotificationManager) mContext.getSystemService(Context.NOTIFICATION_SERVICE);
    }

    @Override
    public void onAvailable(Network network) {
        super.onAvailable(network);
        // 网络连接成功
        Log.d("ConnectivityReceiver", "Network available");
    }

    @Override
    public void onLost(Network network) {
        super.onLost(network);
        // 网络连接丢失
        Log.d("ConnectivityReceiver", "Network lost");
    }

    @Override
    public void onCapabilitiesChanged(Network network, NetworkCapabilities capabilities) {
        super.onCapabilitiesChanged(network, capabilities);
        // 网络连接状态改变
        if (capabilities.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR)) {
            // 移动数据网络连接
            Log.d("ConnectivityReceiver", "Mobile data connected");
            // 发送通知
            NotificationCompat.Builder builder = new NotificationCompat.Builder(mContext)
                    .setSmallIcon(R.drawable.ic_notification)
                    .setContentTitle("Network changed")
                    .setContentText("Switched to mobile data")
                    .setPriority(NotificationCompat.PRIORITY_HIGH);

            mNotificationManager.notify(NOTIFICATION_ID, builder.build());
        } else {
            // WiFi 连接
            Log.d("ConnectivityReceiver", "WiFi connected");
        }
    }
}

要使用 NetworkCallback，您需要在 AndroidManifest.xml 文件中声明 ACCESS_NETWORK_STATE 和 CHANGE_NETWORK_STATE 权限：

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

然后，您需要在您的 Activity 或 Service 中注册 ConnectivityReceiver：

ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
ConnectivityReceiver connectivityReceiver = new ConnectivityReceiver(this);
connectivityManager.registerDefaultNetworkCallback(connectivityReceiver);

这样，您就可以在网络连接状态发生变化时收到通知，包括 WiFi 切换到移动数据的事件。