This code snippet defines a custom "Bounce Edge Effect" for a RecyclerView in Android, replacing the default edge glow effect with a bounce animation.

BounceEdgeEffectFactory.kt

import android.graphics.Canvas
import android.widget.EdgeEffect
import androidx.dynamicanimation.animation.SpringAnimation
import androidx.dynamicanimation.animation.SpringForce
import androidx.recyclerview.widget.RecyclerView

/** The magnitude of translation distance while the list is over-scrolled. */
private const val OVERSCROLL_TRANSLATION_MAGNITUDE = 0.5f

/** The magnitude of translation distance when the list reaches the edge on fling. */
private const val FLING_TRANSLATION_MAGNITUDE = 0.5f

/**
 * Replace edge effect by a bounce
 */
class BounceEdgeEffectFactory(val isVertical: Boolean = true) : RecyclerView.EdgeEffectFactory() {
    override fun createEdgeEffect(recyclerView: RecyclerView, direction: Int): EdgeEffect {
        return object : EdgeEffect(recyclerView.context) {
            // A reference to the [SpringAnimation] for this RecyclerView used to bring the item back after the over-scroll effect.
            var translationAnim: SpringAnimation? = null

            override fun onPull(deltaDistance: Float) {
                super.onPull(deltaDistance)
                handlePull(deltaDistance)
            }

            override fun onPull(deltaDistance: Float, displacement: Float) {
                super.onPull(deltaDistance, displacement)
                handlePull(deltaDistance)
            }

            private fun handlePull(deltaDistance: Float) {
                // This is called on every touch event while the list is scrolled with a finger.

                // Translate the recyclerView with the distance
                if (isVertical) {
                    val sign = if (direction == DIRECTION_BOTTOM) -1 else 1
                    val translationYDelta = sign * recyclerView.width * deltaDistance * OVERSCROLL_TRANSLATION_MAGNITUDE
                    recyclerView.translationY += translationYDelta
                } else {
                    val sign = if (direction == DIRECTION_RIGHT) -1 else 1
                    val translationXDelta = sign * recyclerView.height * deltaDistance * OVERSCROLL_TRANSLATION_MAGNITUDE
                    recyclerView.translationX += translationXDelta
                }

                translationAnim?.cancel()
            }

            override fun onRelease() {
                super.onRelease()
                // The finger is lifted. Start the animation to bring translation back to the resting state.
                if ((if (isVertical) recyclerView.translationY else recyclerView.translationX) != 0f) {
                    translationAnim = createAnim()?.also { it.start() }
                }
            }

            override fun onAbsorb(velocity: Int) {
                super.onAbsorb(velocity)

                // The list has reached the edge on fling.
                val sign = if (direction == if (isVertical) DIRECTION_BOTTOM else DIRECTION_RIGHT) -1 else 1
                val translationVelocity = sign * velocity * FLING_TRANSLATION_MAGNITUDE
                translationAnim?.cancel()
                translationAnim = createAnim().setStartVelocity(translationVelocity)?.also { it.start() }
            }

            override fun draw(canvas: Canvas?): Boolean {
                // don't paint the usual edge effect
                return false
            }

            override fun isFinished(): Boolean {
                // Without this, will skip future calls to onAbsorb()
                return translationAnim?.isRunning?.not() ?: true
            }

            private fun createAnim(): SpringAnimation {
                return SpringAnimation(
                    recyclerView,
                    if (isVertical) SpringAnimation.TRANSLATION_Y else SpringAnimation.TRANSLATION_X
                ).setSpring(
                    SpringForce()
                        .setFinalPosition(0f)
                        .setDampingRatio(SpringForce.DAMPING_RATIO_MEDIUM_BOUNCY)
                        .setStiffness(SpringForce.STIFFNESS_LOW)
                )
            }
        }
    }
}