Type Mismatch in Kotlin with an interface

Question

I have a problem with an implementation of an interface, I tried some things but without success.

And I don't know what else to try, so I ask for your help, thank you in advance.

My GPSUtils.kt

class GPSUtils(context: Context) {

    private var context: Context
    private var mSettingsClient: SettingsClient
    private var mLocationSettingsRequest: LocationSettingsRequest
    private var locationManager: LocationManager
    private var locationRequest: LocationRequest

    init {
        this.context = context
        locationManager = context.getSystemService(Context.LOCATION_SERVICE) as LocationManager
        mSettingsClient = LocationServices.getSettingsClient(context)
        locationRequest = LocationRequest.create()
        locationRequest.priority = LocationRequest.PRIORITY_HIGH_ACCURACY
        locationRequest.interval = (10 * 1000).toLong()
        locationRequest.fastestInterval = (2 * 1000).toLong()
        val builder = LocationSettingsRequest.Builder().addLocationRequest(locationRequest)
        mLocationSettingsRequest = builder.build()
        builder.setAlwaysShow(true) //this is the key ingredient
    }

    fun turnGPSOn(onGpsListener: OnGpsListener) {
        if (locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)) {
            if (onGpsListener != null) {
                onGpsListener!!.gpsStatus(true)
            }
        } else {
            mSettingsClient.checkLocationSettings(mLocationSettingsRequest)
                .addOnSuccessListener(context as Activity) {
                    if (onGpsListener != null) {
                        onGpsListener!!.gpsStatus(true)
                    }
                }.addOnFailureListener(context as Activity) { e ->
                    val statusCode = (e as ApiException).statusCode
                    when (statusCode) {
                        LocationSettingsStatusCodes.RESOLUTION_REQUIRED -> try {
                            val rae = e as ResolvableApiException
                            rae.startResolutionForResult(context as Activity, 1001)
                        } catch (sie: IntentSender.SendIntentException) { Log.i(TAG, "PendingIntent unable to execute request.") }

                        LocationSettingsStatusCodes.SETTINGS_CHANGE_UNAVAILABLE -> {
                            val errorMessage = "Location settings are inadequate, and cannot be " + "fixed here. Fix in Settings."
                            Log.e(TAG, errorMessage)
                            Toast.makeText(context as Activity, errorMessage, Toast.LENGTH_LONG).show()
                        }
                    }
                }
        }
    }

    interface OnGpsListener {
        fun gpsStatus(isGPSEnable: Boolean)
    }

}

My AssigmentFragment.kt

class AssigmentFragment : Fragment() {

    var isGPS: Boolean = false

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {

        val rootView = inflater.inflate(R.layout.fragment_assigment, container, false)

        GPSUtils(activity!!).turnGPSOn { isGPSEnable ->
            isGPS = isGPSEnable
        }
    }
}

And I got this error:

I don't know what else to try, ideas are welcome. Thank you in advance for the help.

Answer 1

If you really want to use that short notation., you can write your interface in Java:

interface OnGpsListener {
   void gpsStatus(boolean isGPSEnable);
}

This way you can use it in your kotlin code in the following way:

GPSUtils(activity!!).turnGPSOn(OnGpsListener { isGPSEnable ->
    isGPS = isGPSEnable
})

The problem is that SAM convertions are available only for java interfaces, this article explains some things about that:

krossovochkin: kotlin java interop function references and sam conversions

And if you are porting java code to kotlin, maybe presenving java interfaces is convenient, as this SO answer says.

Answer 2

Try this:

GPSUtils(activity!!).turnGPSOn(object: GPSUtils.OnGpsListener {
     override fun gpsStatus(isGPSEnable: Boolean) {
           // Code block ...
     }
})