class MyAdapter(fm: FragmentManager) : SlideFragmentAdapter(fm) {

    private val data = listOf("a", "b", "c", "d")
    private var currentIndex = 0

    /**
     * Whether it can slide in the direction of [direction].
     */
    override fun canSlideTo(direction: SlideDirection): Boolean {
        val index =
            when (direction) {
                SlideDirection.Next -> currentIndex + 1 //can slide to next page
                SlideDirection.Prev -> currentIndex - 1 //can slide to previous page
                else -> currentIndex
            }
        return index in 0 until data.size
    }

    /**
     * Called by [SlidableLayout] to create the content [Fragment].
     */
    override fun onCreateFragment(context: Context): Fragment {
        return DemoFragment()
    }

    /**
     * Called by [SlidableLayout] when the [fragment] starts to slide to visible.
     * This method should update the contents of the [fragment] to reflect the
     * item at the [direction].
     */
    override fun onBindFragment(fragment: Fragment, direction: SlideDirection) {
        val index =
            when (direction) {
                SlideDirection.Next -> currentIndex + 1 //to next page
                SlideDirection.Prev -> currentIndex - 1 //to previous page
                SlideDirection.Origin -> currentIndex
            }
        //bind data to the ui
        (fragment as DemoFragment).currentData = data[index]
    }

    /**
     * Called by [SlidableLayout] when the view finishes sliding.
     */
    override fun finishSlide(direction: SlideDirection) {
        super.finishSlide(direction)
        //update current index
        currentIndex =
            when (direction) {
                SlideDirection.Next -> currentIndex + 1 //already to next page
                SlideDirection.Prev -> currentIndex - 1 //already to previous page
                SlideDirection.Origin -> currentIndex //rebound to origin page
            }
    }
}

slidable_layout.setAdapter(MyAdapter(supportFragmentManager))

class DemoFragment : Fragment(), SlidableUI {

    override fun startVisible(direction: SlideDirection) {
        //At the beginning of the slide, the current view will be visible.
        //Binding data into view can be implemented in this callback,
        //such as displaying place holder pictures.
    }

    override fun completeVisible(direction: SlideDirection) {
        //After sliding, the current view is completely visible.
        //You can start the main business in this callback,
        //such as starting to play video, page exposure statistics...
    }

    override fun invisible(direction: SlideDirection) {
        //After sliding, the current view is completely invisible.
        //You can do some cleaning work in this callback,
        //such as closing the video player.
    }

    override fun preload(direction: SlideDirection) {
        //Have completed a sliding in the direction, and the user is likely to
        //continue sliding in the same direction. 
        //You can preload the next page in this callback,
        //such as download the next video or prepare the cover image.
    }
}