WiFiConnectUseCase.kt

class WiFiConnectUseCase(context: Context) {

    private var wifiManager = 
        context.applicationContext.getSystemService(Context.WIFI_SERVICE) as WifiManager

    private val connectivityManager =
        context.applicationContext.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager

    private val wifiSSID = "My Network"
    private val wifiPassword = "password1234"
                                                                                        
    @RequiresApi(api = Build.VERSION_CODES.Q)
    operator fun invoke(): Single<Pair<Network, ConnectivityManager.NetworkCallback>> { //return the NetworkCallback in order to disconnect properly from the device
        return connect()
            .delay(3, TimeUnit.SECONDS) // wait for 3 sec, just to make sure everything is configured on the device
    }

    @RequiresApi(Build.VERSION_CODES.Q)
    private fun connect(): Single<Pair<Network, ConnectivityManager.NetworkCallback>> {
        return Single.create { emitter ->
                              
            val specifier = WifiNetworkSpecifier.Builder()
                .setSsid(wifiSSID)
                .setWpa2Passphrase(wifiPassword)
                .build()
                              
            val networkRequest = NetworkRequest.Builder()
                .addTransportType(NetworkCapabilities.TRANSPORT_WIFI)
                .removeCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET) // as not internet connection is required for this device
                .setNetworkSpecifier(specifier)
                .build()
                              
            val networkCallback = object : ConnectivityManager.NetworkCallback() {
                override fun onAvailable(network: Network) {
                    super.onAvailable(network)
                    Timber.v("connect to WiFi success. Network is available.")
                    emitter.onSuccess(Pair(network, this))
                }

                override fun onUnavailable() {
                    super.onUnavailable()
                    Timber.w("connect to WiFi failed. Network is unavailable")
                    emitter.tryOnError(IllegalArgumentException("connect to WiFi failed. Network is unavailable"))
                }
            }
                              
            connectivityManager.requestNetwork(networkRequest, networkCallback)
        }
    }
}