LinearLayoutManager subclass that "peeks", shows a portion of the adjacent child views.

PeekingLinearLayoutManager.kt

class PeekingLinearLayoutManager : LinearLayoutManager {
    @Suppress("Unused")
    @JvmOverloads
    constructor(context: Context?, @RecyclerView.Orientation orientation: Int = RecyclerView.VERTICAL, reverseLayout: Boolean = false) : super(context, orientation, reverseLayout)

    @Suppress("Unused")
    constructor(context: Context, attrs: AttributeSet, defStyleAttr: Int, defStyleRes: Int) : super(context, attrs, defStyleAttr, defStyleRes)

    override fun generateDefaultLayoutParams() =
            scaledLayoutParams(super.generateDefaultLayoutParams())

    override fun generateLayoutParams(lp: ViewGroup.LayoutParams?) =
            scaledLayoutParams(super.generateLayoutParams(lp))

    override fun generateLayoutParams(c: Context?, attrs: AttributeSet?) =
            scaledLayoutParams(super.generateLayoutParams(c, attrs))

    private fun scaledLayoutParams(layoutParams: RecyclerView.LayoutParams) =
            layoutParams.apply {
                when(orientation) {
                    HORIZONTAL -> width = (horizontalSpace * ratio).toInt()
                    VERTICAL -> height = (verticalSpace * ratio).toInt()
                }
            }

    private val horizontalSpace get() = width - paddingStart - paddingEnd

    private val verticalSpace get() = height - paddingTop - paddingBottom

    private val ratio = 0.9f
}

Based on and inspired by https://gist.github.com/heinrichreimer/39f9d2f9023a184d96f8

You should use height for the verticalSpace calculation. Tnx for the code!

Good catch!

You might want to add the following change to avoid showing an empty space when there is a single item:

 private fun scaledLayoutParams(layoutParams: RecyclerView.LayoutParams): RecyclerView.LayoutParams {
        if (itemCount == 1) {
            return layoutParams
        }

        return layoutParams.apply {
            when (orientation) {
                HORIZONTAL -> width = (horizontalSpace * ratio).toInt()
                VERTICAL -> height = (verticalSpace * ratio).toInt()
            }
        }
    }

It is not working when we have item height more than item width