class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val items = listOf<AppCompatEditText>(et1, et2, et3, et4, et5, et6, et7, et8, et9, et10, et11, et12,
                et13, et14, et15, et16, et17, et18, et19, et20, et21, et22, et23)

        items.forEachIndexed { index, et -> et.hint = "index : $index" }

        scrollView.viewTreeObserver.addOnGlobalFocusChangeListener { old, _ ->
            // TODO : how to check next focus edittext
            old?.takeIf { keyboardIsShow() }?.apply {
                scrollView.smoothScrollTo(0, scrollView.scrollY.plus(120))
            }
        }
    }
}

// TODO : move to file UIExtensions
fun Activity.keyboardIsShow(): Boolean = let {
    var flag = false
    val rect: Rect by lazy { Rect() }
    window.decorView.rootView?.apply {
        getWindowVisibleDisplayFrame(rect)
        flag = (bottom - rect.bottom) > (100 * resources.displayMetrics.density)
    }
    flag
}