Rotation.kt

class SpringRotationView @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0) : View(context, attrs, defStyleAttr) {

    private companion object Params {
        val INITIAL_ROTATION = 0f
        val STIFFNESS = SpringForce.STIFFNESS_MEDIUM
        val DAMPING_RATIO = SpringForce.DAMPING_RATIO_HIGH_BOUNCY
    }

    private val rotationAnim: SpringAnimation = SpringAnimation(this, SpringAnimation.ROTATION).apply {
        spring = SpringForce(INITIAL_ROTATION).apply {
            stiffness = STIFFNESS
            dampingRatio = DAMPING_RATIO
        }
    }

    init {
        var currentRotation = 0f
        setOnTouchListener { view, event ->

            when (event.actionMasked) {
                MotionEvent.ACTION_DOWN -> {
                    rotationAnim.cancel()

                    currentRotation = rotationAmount(event.x, event.y)
                }
                MotionEvent.ACTION_MOVE -> {
                    val previousRotation = currentRotation

                    currentRotation = rotationAmount(event.x, event.y)
                    view.rotation += currentRotation - previousRotation
                }
                MotionEvent.ACTION_UP -> rotationAnim.start()
            }
            true
        }
    }

}