app to display - current time in different timezones - keeping this for reference

activity_dummy.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/LinearLayout1"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center|top"
    android:orientation="vertical"
    android:padding="5dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:orientation="vertical">

        <TextView
            android:id="@+id/txtGMTTime"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/current" />

        <TextView
            android:id="@+id/txtCurrentTime"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            tools:context=".MainActivity"
            tools:text="txtCurrentTime" />
    </LinearLayout>

    <Spinner
        android:id="@+id/availableID"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:orientation="vertical">

        <TextView
            android:id="@+id/timezone"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            tools:text="timeZone" />

        <TextView
            android:id="@+id/txtTimeZoneTime"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            tools:text="txtTimeZoneTime" />
    </LinearLayout>

</LinearLayout>

DummyActivity.kt

//  based on http://www.theappguruz.com/blog/android-time-zone-demo

class DummyActivity : Activity() {
    private var spinnerAvailableID: Spinner? = null
    private var current: Calendar? = null
    private var textTimeZone: TextView? = null
    private var txtCurrentTime: TextView? = null
    private var txtTimeZoneTime: TextView? = null
    private var miliSeconds: Long = 0
    private var idAdapter: ArrayAdapter<String>? = null
    private var sdf: SimpleDateFormat? = null
    private var resultdate: Date? = null

    /**
     * Called when the activity is first created.
     */
    public override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_dummy)
        spinnerAvailableID = findViewById<View>(R.id.availableID) as Spinner
        textTimeZone = findViewById<View>(R.id.timezone) as TextView
        txtCurrentTime = findViewById<View>(R.id.txtCurrentTime) as TextView
        txtTimeZoneTime = findViewById<View>(R.id.txtTimeZoneTime) as TextView
        val idArray = TimeZone.getAvailableIDs()
        sdf = SimpleDateFormat("EEEE, dd MMMM yyyy HH:mm:ss")
        idAdapter = ArrayAdapter(this, android.R.layout.simple_spinner_item, idArray)
        idAdapter!!.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
        spinnerAvailableID!!.adapter = idAdapter
        getGMTTime()
        spinnerAvailableID!!.onItemSelectedListener = object : OnItemSelectedListener {

            override fun onItemSelected(parent: AdapterView<*>,
                                        view: View,
                                        position: Int,
                                        id: Long) {
                getGMTTime()
                val selectedId = parent.getItemAtPosition(position) as String
                val timezone = TimeZone.getTimeZone(selectedId)
                val timeZoneName = timezone.displayName
                val timeZoneOffset = (timezone.rawOffset / (60 * 1000))
                val hrs = timeZoneOffset / 60
                val mins = timeZoneOffset % 60
                miliSeconds += timezone.rawOffset
                resultdate = Date(miliSeconds)
                println("yup onItemSelected(): " + sdf!!.format(resultdate))
                textTimeZone!!.text = ("$timeZoneName : GMT $hrs.$mins")
                txtTimeZoneTime!!.text = "" + sdf!!.format(resultdate)
                miliSeconds = 0
            }

            override fun onNothingSelected(arg0: AdapterView<*>?) {}
        }
    }

    // Convert Local Time into GMT time
    // Convert Local Time into GMT time
    private fun getGMTTime() {
        current = Calendar.getInstance()
        txtCurrentTime!!.text = "" + current!!.getTime()
        miliSeconds = current!!.timeInMillis
        val tzCurrent = current!!.timeZone
        var offset = tzCurrent.rawOffset
        if (tzCurrent.inDaylightTime(Date())) {
            offset += tzCurrent.dstSavings
        }
        miliSeconds -= offset
        resultdate = Date(miliSeconds)
        println("yup getGMTTime(): " + sdf!!.format(resultdate))
    }
}