Draw bottom divider in RecyclerView with customisable show/hide divider and paddings for each item #android

DividerItemDecoration.kt

import android.content.Context
import android.graphics.Canvas
import android.graphics.Paint
import android.graphics.RectF
import android.support.annotation.ColorRes
import android.support.v4.content.res.ResourcesCompat
import android.support.v4.view.ViewCompat
import android.support.v7.widget.RecyclerView
import org.jetbrains.anko.dip


class DividerItemDecoration(
        private val context: Context,
        private @param:ColorRes val dividerColorResId: Int = R.color.divider,
        private val shouldDrawDivider: (Int, Int) -> Boolean = { _, _ -> true },
        private val dividerPaddingStart: (Int, Int) -> Int = { _, _ -> 0 },
        private val dividerPaddingEnd: (Int, Int) -> Int = { _, _ -> 0 }
) : RecyclerView.ItemDecoration() {
    private val dividerPaint = Paint()

    init {
        dividerPaint.color = ResourcesCompat.getColor(context.resources, dividerColorResId, null)
    }

    override fun onDraw(c: Canvas, parent: RecyclerView, state: RecyclerView.State?) {
        super.onDraw(c, parent, state)
        if (parent.layoutManager == null) return
        drawDividers(c, parent)
    }

    private fun drawDividers(c: Canvas, parent: RecyclerView) {
        for (i in 0 until parent.childCount) {
            val child = parent.getChildAt(i)
            val adapterPosition = parent.getChildAdapterPosition(child)
            if (adapterPosition == RecyclerView.NO_POSITION) {
                continue
            }
            val childType = parent.adapter.getItemViewType(adapterPosition)

            if (i != parent.childCount - 1 && shouldDrawDivider(adapterPosition, childType)) {
                val isRtlLayout = ViewCompat.getLayoutDirection(parent) == ViewCompat.LAYOUT_DIRECTION_RTL

                val paddingStart = dividerPaddingStart(adapterPosition, childType)
                val paddingEnd = dividerPaddingEnd(adapterPosition, childType)
                val paddingLeft = if (isRtlLayout) paddingEnd else paddingStart
                val paddingRight = if (isRtlLayout) paddingStart else paddingEnd

                val dividerHeight = context.dip(1)
                val rect = RectF(
                        child.left.toFloat() + paddingLeft,
                        child.bottom.toFloat() - dividerHeight,
                        child.right.toFloat() - paddingRight,
                        child.bottom.toFloat()
                )
                c.drawRect(rect, dividerPaint)
            }
        }
    }
}