lazyview.kt

private class LazyView<T>(view : View, res : Int) : ReadWriteProperty<Any?, T> {

    private var mView: View = view
    private var res : Int = res
    private var mValue: T? = null

    override fun getValue(thisRef: Any?, property: KProperty<*>): T {
        mValue = mValue ?: mView.findViewById(res) as T
        return mValue!!
    }

    override fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
        throw UnsupportedOperationException()
    }
}

var imageView by LazyView<ImageView>(this, R.id.imageview)