Many apps require a network connection. Provided the connection meets bandwidth requirements, the apps don’t typically care how that connection is established. But for applications that engage in controlling home devices the application may specifically want to communicate over WiFi. In Android there are two ways that this has been handled. Some applications will turn on WiFi if it is turned off. Others may prompt the user to turn on WiFi.

Of the two options, the application turning on WiFi is an approach that is not supported on Android Q and later. This is part of the privacy changes in Android Q. For older versions of Android, controlling the WiFi could be performed though the WIFI_SERVICE.

val wifi = getSystemService(WIFI_SERVICE) as WifiManager
if(!wifi.isWifiEnabled)
    wifi.isWifiEnabled = true;

If you try this now, Android Studio will give a deprecation warning. To have the user change the WiFi state the application can open the WiFi control interface for the user. Rather than dump the user into the WiFi control interface, it is generally better to prompt them first. The WiFi control UI can be opened with an intent for ACTION_WIRELESS_SETTINGS.

startActivity(Intent(Settings.ACTION_WIRELESS_SETTINGS));

An easy way to prompt the user is to use the AlertDialogBuilder. A complete solution looks like the following.

    fun checkWifiState() {
        val wifi = getSystemService(WIFI_SERVICE) as WifiManager
        if(!wifi.isWifiEnabled) {

            val dialogClickListener =
                DialogInterface.OnClickListener { dialog, which ->
                    when (which) {
                        DialogInterface.BUTTON_POSITIVE -> {
                            startActivity(Intent(Settings.ACTION_WIRELESS_SETTINGS));
                        }
                        DialogInterface.BUTTON_NEGATIVE -> {
                        }
                    }
                }

            var builder:AlertDialog.Builder = AlertDialog.Builder(this) as AlertDialog.Builder
            builder.setMessage("WiFi must be enabled. Do you want to open the WiFi controls?")
                .setPositiveButton("Yes", dialogClickListener)
                .setNegativeButton("No", dialogClickListener)
                .show()
        }
    }