Simulated switch is "null", cannot perform actions

Developer Programs Writing SmartApps
#1

Hello,

I have this SmartApp that should turn on a simulated switch, but when i do “switch.on()” a NullPointerException is thrown, because switch is null.
Yet, the correct device and name are selected in the preferences. Let me link some code.

preferences {  //Set the sensor and the relay
    section("Choose devices"){
	input "sensor", "capability.temperatureMeasurement", required: true, title: "Sensore di temperatura"
        input "device", "capability.switch", required: true, title: "Relay"
    }
//Cut out due to lenght, i have other 16 preferences...
}

And…

if (temperature < workTime1Temperature) device?.on();
    else device?.off();  //Safe navigation to avoid exception
    log.info("${device}");  //This prints "null"
}

Here are some screenshots from the SmartThings app.

I don’t get it. The device is configured correctly… selected in the list…
May the Virtual Device have an influence on this?

Thanks to everyone in advance

#2

Please, it is nearly always more helpful to post a GitHub link to your FULL CODE if you want help debugging.

That way the helper can just copy/paste the SmartApp into their IDE and replicate the error and respond with just a couple edits!

If you suspect a Virtual Device issue, then test using a Physical Device!