vertical_page_transformer.kt

class PageTransformer : ViewPager2.PageTransformer {
    companion object {
        private const val SCALE = 0.9f
    }

    override fun transformPage(view: View, position: Float) {
        val translationOffset = calculateTranslationOffset(view, position)
        with(view) {
            when {
                position < -2.5 -> {
                    alpha = 0f
                    scaleX = 1f
                    scaleY = 1f
                }
                position < -1 -> {
                    alpha = 1f
                    translationY = translationOffset
                    setScale(this, -1f)
                }
                position <= 0 -> {
                    translationY = translationOffset
                    setScale(this, position)
                }
                position > 0.9 -> {
                    alpha = 0f
                    translationY = translationOffset
                }
                position > 0 -> {
                    alpha = 1f
                    translationY = translationOffset
                }
            }
        }
    }

    private fun setScale(view: View, position: Float) {
        val scale = (SCALE + (1 - SCALE) * (1 - Math.abs(position)))
        view.scaleY = scale
        view.scaleX = scale
    }

    private fun calculateTranslationOffset(view: View, position: Float): Float {
        val additionalOffsetScale = StrictMath.pow(1.0 / 10.0, -position.toDouble())
        val additionalOffset = additionalOffsetScale * (view.height * 0.1)
        return (additionalOffset + (position * -view.height * SCALE)).toFloat()
    }
}