StackPanel seems to not indexing components properly about kvision HOT 4 CLOSED

data class StackPanelBindings(
    val tx: Text,
    val btn: Button
)

val index = ObservableValue(
    StackPanelBindings(
        Text(floating = true, label = "this is label"),
        Button(text = "Click me!")
    ) 
)

stackPanel().bind(
    index
) {binding ->
    add(binding.btn)
    add(binding.tx)

    binding.btn.onClick {
        activeChild = binding.tx
    }
    activeChild = binding.btn
}

            val index = ObservableValue(0) // 0  - show button first

            simplePanel().bind(index) {
                if (it == 0) {
                    button(text = "Click me!") {
                        onClick {
                            index.value = 1
                        }
                    }
                } else {
                    text(floating = true, label = "this is label")
                }
            }
            span().bind(index) {
                +"${it}"
            }

            val index = ObservableValue(0) // 0  - show button first

            var text: Text? = null
            simplePanel().bind(index) {
                if (it == 0) {
                    button(text = "Click me!") {
                        onClick {
                            index.value = 1
                        }
                    }
                } else {
                    text = text(floating = true, label = "this is label")
                }
            }
            span().bind(index) {
                +"${it}"
            }
            button("set new value") {
                onClick {
                    text?.value = "new value"
                }
            }

            val index = ObservableValue(0) // 0  - show button first

            val txChild = Text(floating = true, label = "this is label")
            val btn = Button(text = "Click me!") {
                onClick {
                    index.value = 1
                }
            }

            stackPanel {
                add(btn)
                add(txChild)
                index.subscribe {
                    activeIndex = it
                }
            }

            span().bind(index) {
                +"${it}"
            }