Vertical View Pager

VerticalViewPager.kt

package ru.werbary.tv1000play.mobile.view

import android.content.Context
import android.support.v4.view.ViewPager
import android.util.AttributeSet
import android.view.MotionEvent
import android.view.View


/**
 * @since 2017
 * @author Anton Vlasov - whalemare
 */
class VerticalViewPager @JvmOverloads constructor(
        context: Context,
        attrs: AttributeSet? = null
) : ViewPager(context, attrs) {

    val VERTICAL = 1

    private var mSwipeOrientation: Int = VERTICAL

    init {
        // The majority of the work is done over here
        setPageTransformer(true, VerticalPageTransformer())
        // The easiest way to get rid of the overscroll drawing that happens on the left and right
        overScrollMode = View.OVER_SCROLL_NEVER
    }

    override fun onTouchEvent(event: MotionEvent): Boolean {
        return super.onTouchEvent(if (mSwipeOrientation == VERTICAL) swapXY(event) else event)
    }

    override fun canScrollHorizontally(direction: Int): Boolean {
        return false
    }

    override fun canScrollVertically(direction: Int): Boolean {
        return true
    }

    override fun onInterceptTouchEvent(event: MotionEvent): Boolean {
        if (mSwipeOrientation == VERTICAL) {
            val intercepted = super.onInterceptHoverEvent(swapXY(event))
            swapXY(event)
            return intercepted
        }
        return super.onInterceptTouchEvent(event)
    }

    private fun swapXY(event: MotionEvent): MotionEvent {
        val width = width.toFloat()
        val height = height.toFloat()

        val newX = event.y / height * width
        val newY = event.x / width * height

        event.setLocation(newX, newY)
        return event
    }

    private inner class VerticalPageTransformer : ViewPager.PageTransformer {

        override fun transformPage(page: View, position: Float) = when {
        // This page is way off-screen to the leftL
            position < -1 -> {
                page.setAlpha(0F)
            }
            position <= 1 -> {
                page.alpha = 1F

                // Counteract the default slide transition
                page.translationX = page.width * -position

                // set Y position to swipe in from top
                val yPosition = position * page.height
                page.setTranslationY(yPosition)
            }
        // This page is way off screen to the right
            else -> page.setAlpha(0F)
        }
    }

}