setViewHeight.kt

private fun setViewHeight() {
        intro.viewTreeObserver.addOnGlobalLayoutListener(
            object : OnGlobalLayoutListener {
                override fun onGlobalLayout() {
                    oldHeight = intro.getHeight()
                    intro.viewTreeObserver.removeOnGlobalLayoutListener(this)
                }
            })

        detail.viewTreeObserver.addOnGlobalLayoutListener(
            object : OnGlobalLayoutListener {
                override fun onGlobalLayout() {
                    newHeight = detail.getHeight()
                    detail.viewTreeObserver.removeOnGlobalLayoutListener(this)
                    detail.visibility = View.GONE
                }
            })
    }