GenericSwipeCallback.kt

import android.graphics.Canvas
import android.support.v7.widget.RecyclerView
import android.support.v7.widget.helper.ItemTouchHelper
import android.support.v7.widget.helper.ItemTouchHelper.*
import android.view.View
import com.stronix.lio.ui.features.broadcasts.BroadcastsSwipeCallback

abstract class GenericSwipeCallback(
        private var swipeLeft: SwipeAction? = null,
        private var swipeRight: SwipeAction? = null
) : ItemTouchHelper.Callback() {

    private var isViewBeingCleared = false

    override fun getMovementFlags(recyclerView: RecyclerView,
                                  viewHolder: RecyclerView.ViewHolder): Int
            = makeMovementFlags(ACTION_STATE_IDLE, getAvailableDirections())

    abstract fun getAvailableDirections(): Int

    override fun onMove(recyclerView: RecyclerView?, viewHolder: RecyclerView.ViewHolder,
                        target: RecyclerView.ViewHolder?): Boolean = false

    override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
        val adapterPosition = viewHolder.adapterPosition
        return when (direction) {
            ItemTouchHelper.LEFT -> onSwipeLeft(adapterPosition)
            ItemTouchHelper.START -> onSwipeLeft(adapterPosition)
            ItemTouchHelper.RIGHT -> onSwipeRight(adapterPosition)
            ItemTouchHelper.END -> onSwipeRight(adapterPosition)
            else -> {
            }
        }
    }

    override fun clearView(recyclerView: RecyclerView?, viewHolder: RecyclerView.ViewHolder) {
        isViewBeingCleared = true
        val view = viewHolder.itemView
        ItemTouchHelper.Callback.getDefaultUIUtil().clearView(view)
        view.alpha = BroadcastsSwipeCallback.ALPHA_COMPLETED
    }

    override fun onChildDraw(canvas: Canvas, recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder,
                             dX: Float, dY: Float, actionState: Int, isCurrentlyActive: Boolean) {
        if (isViewBeingCleared) {
            isViewBeingCleared = false
        } else {
            val itemView = viewHolder.itemView
            if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
                if (viewHolder.adapterPosition == -1) {
                    return
                }

                processSwipeAction(canvas, itemView, dX)
            } else {
                ItemTouchHelper.Callback.getDefaultUIUtil()
                        .onDraw(canvas, recyclerView, itemView, dX, dY, actionState, isCurrentlyActive)
            }
        }
    }

    private fun processSwipeAction(canvas: Canvas, itemView: View, dX: Float) {
        hideItemDependingOnDx(dX, itemView)

        if (getSwipeDirection(dX) == RIGHT) {
            drawBackgroundWhenSwipeRight(canvas, dX, itemView)
            drawSwipeRightIcon(canvas, itemView)
        } else {
            drawBackgroundWhenSwipeLeft(canvas, dX, itemView)
            drawSwipeLeftIcon(canvas, itemView)
        }
    }

    private fun hideItemDependingOnDx(dX: Float, itemView: View) {
        val alpha = BroadcastsSwipeCallback.ALPHA_COMPLETED - Math.abs(dX) / itemView.width.toFloat()
        itemView.alpha = alpha
        itemView.translationX = dX
    }

    private fun drawBackgroundWhenSwipeLeft(c: Canvas, dX: Float, itemView: View) {
        swipeLeft?.background?.apply {
            setBounds((itemView.right + dX).toInt(), itemView.top, itemView.right, itemView.bottom)
            draw(c)
        }
    }

    private fun drawBackgroundWhenSwipeRight(c: Canvas, dX: Float, itemView: View) {
        swipeRight?.background?.apply {
            setBounds(0, itemView.top, (itemView.left + dX).toInt(), itemView.bottom)
            draw(c)
        }
    }

    private fun getSwipeDirection(dX: Float) = if (dX > 0) RIGHT else LEFT

    private fun drawSwipeLeftIcon(c: Canvas, itemView: View) {
        val margin = swipeLeft?.margin ?: 0
        swipeLeft?.icon?.let {
            val itemMiddlePoint = getItemMiddlePoint(itemView)
            val intrinsicHalfHeight = it.intrinsicHeight / 2
            val intrinsicWidth = it.intrinsicWidth

            val right = itemView.right - margin
            val left = right - intrinsicWidth
            val top = itemMiddlePoint - intrinsicHalfHeight
            val bottom = itemMiddlePoint + intrinsicHalfHeight

            it.setBounds(left, top, right, bottom)
            it.draw(c)
        }
    }

    private fun drawSwipeRightIcon(c: Canvas, itemView: View) {
        val margin = swipeRight?.margin ?: 0
        swipeRight?.icon?.let {
            val itemMiddlePoint = getItemMiddlePoint(itemView)
            val intrinsicHalfHeight = it.intrinsicHeight / 2
            val intrinsicWidth = it.intrinsicWidth

            val left = itemView.left + margin
            val right = left + intrinsicWidth
            val top = itemMiddlePoint - intrinsicHalfHeight
            val bottom = itemMiddlePoint + intrinsicHalfHeight

            it.setBounds(left, top, right, bottom)
            it.draw(c)
        }
    }

    private fun getItemMiddlePoint(itemView: View) = (itemView.bottom + itemView.top) / 2

    private fun onSwipeLeft(adapterPosition: Int) {
        swipeLeft?.action?.invoke(adapterPosition)
    }

    private fun onSwipeRight(adapterPosition: Int) {
        swipeRight?.action?.invoke(adapterPosition)
    }
}

RecyclerViewSwipeDslExample.kt

            swipe {
                left {
                    color = ContextCompat.getColor(context, R.color.message_swipe_delete)
                    icon = drawableLeft
                    iconMargin = margin
                    action = {
                        // TODO
                    }
                }
                right {
                    color = ContextCompat.getColor(context, R.color.message_swipe_reply)
                    icon = drawableRight
                    iconMargin = margin
                    action = {
                        // TODO
                    }
                }
            }

RecyuclerViewExt.kt

fun RecyclerView.addSwipe(swipeController: ItemTouchHelper.Callback) {
    ItemTouchHelper(swipeController).attachToRecyclerView(this)
}

SwipeAction.kt

import android.graphics.drawable.Drawable

class SwipeAction(val background: Drawable? = null,
                  val icon: Drawable? = null,
                  val margin: Int? = 0,
                  val action: (Int) -> Unit)

SwipeDsl.kt

import android.graphics.drawable.ColorDrawable
import android.graphics.drawable.Drawable
import android.support.v7.widget.RecyclerView
import android.support.v7.widget.helper.ItemTouchHelper

@DslMarker
annotation class SwipeDsl

@SwipeDsl
class SwipeActionBuilder {

    var color: Int? = null
    var background: Drawable? = null
    var icon: Drawable? = null
    var iconMargin: Int = 0

    lateinit var action: (Int) -> Unit

    fun build(): SwipeAction = SwipeAction(background ?: color?.let { ColorDrawable(it) },
            icon, iconMargin, action)
}

@SwipeDsl
class SwipeBuilder {
    var swipeLeftBuilder: SwipeActionBuilder? = null
    var swipeRightBuilder: SwipeActionBuilder? = null

    fun build(): ItemTouchHelper.Callback? {

        val swipeLeftAction = swipeLeftBuilder?.build()
        val swipeRightAction = swipeRightBuilder?.build()

        return object : GenericSwipeCallback(swipeLeftAction, swipeRightAction) {
            override fun getAvailableDirections(): Int {
                return when {
                    swipeLeftAction != null && swipeRightAction != null -> ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT
                    swipeLeftAction != null -> ItemTouchHelper.LEFT
                    swipeRightAction != null -> ItemTouchHelper.RIGHT
                    else -> 0
                }
            }

        }
    }

    @SwipeDsl
    fun left(setup: SwipeActionBuilder.() -> Unit) {
        this.swipeLeftBuilder = SwipeActionBuilder().apply(setup)
    }

    @SwipeDsl
    fun right(setup: SwipeActionBuilder.() -> Unit) {
        this.swipeRightBuilder = SwipeActionBuilder().apply(setup)
    }
}

@SwipeDsl
fun recyclerViewSwipe(recyclerView: RecyclerView, setup: SwipeBuilder.() -> Unit) {
    with(SwipeBuilder()) {
        setup()
        build()
    }?.let {
        ItemTouchHelper(it).attachToRecyclerView(recyclerView)
    }
}

fun RecyclerView.swipe(setup: SwipeBuilder.() -> Unit) {
    with(SwipeBuilder()) {
        setup()
        build()
    }?.let {
        ItemTouchHelper(it).attachToRecyclerView(this)
    }
}

fun RecyclerView.leftSwipe(setup: SwipeActionBuilder.() -> Unit) {
    with(SwipeBuilder()) {
        swipeLeftBuilder = SwipeActionBuilder().apply(setup)
        build()
    }?.let {
        ItemTouchHelper(it).attachToRecyclerView(this)
    }
}

fun RecyclerView.rightSwipe(setup: SwipeActionBuilder.() -> Unit) {
    with(SwipeBuilder()) {
        swipeRightBuilder = SwipeActionBuilder().apply(setup)
        build()
    }?.let {
        ItemTouchHelper(it).attachToRecyclerView(this)
    }
}