Android: How to handle right to left swipe gestures

Question

I want my app to recognize when a user swipes from right to left on the phone screen.

How to do this?

Answer 1

Kotlin version of @Mirek Rusin is here:

OnSwipeTouchListener.kt :

open class OnSwipeTouchListener(ctx: Context) : OnTouchListener {

    private val gestureDetector: GestureDetector

    companion object {

        private val SWIPE_THRESHOLD = 100
        private val SWIPE_VELOCITY_THRESHOLD = 100
    }

    init {
        gestureDetector = GestureDetector(ctx, GestureListener())
    }

    override fun onTouch(v: View, event: MotionEvent): Boolean {
        return gestureDetector.onTouchEvent(event)
    }

    private inner class GestureListener : SimpleOnGestureListener() {


        override fun onDown(e: MotionEvent): Boolean {
            return true
        }

        override fun onFling(e1: MotionEvent, e2: MotionEvent, velocityX: Float, velocityY: Float): Boolean {
            var result = false
            try {
                val diffY = e2.y - e1.y
                val diffX = e2.x - e1.x
                if (Math.abs(diffX) > Math.abs(diffY)) {
                    if (Math.abs(diffX) > SWIPE_THRESHOLD && Math.abs(velocityX) > SWIPE_VELOCITY_THRESHOLD) {
                        if (diffX > 0) {
                            onSwipeRight()
                        } else {
                            onSwipeLeft()
                        }
                        result = true
                    }
                } else if (Math.abs(diffY) > SWIPE_THRESHOLD && Math.abs(velocityY) > SWIPE_VELOCITY_THRESHOLD) {
                    if (diffY > 0) {
                        onSwipeBottom()
                    } else {
                        onSwipeTop()
                    }
                    result = true
                }
            } catch (exception: Exception) {
                exception.printStackTrace()
            }

            return result
        }


    }

    open fun onSwipeRight() {}

    open fun onSwipeLeft() {}

    open fun onSwipeTop() {}

    open fun onSwipeBottom() {}
}

Usage:

view.setOnTouchListener(object : OnSwipeTouchListener(context) {

    override fun onSwipeTop() {
        super.onSwipeTop()
    }

    override fun onSwipeBottom() {
        super.onSwipeBottom()
    }

    override fun onSwipeLeft() {
        super.onSwipeLeft()
    }

    override fun onSwipeRight() {
        super.onSwipeRight()
    }
})

the open keyword was the point for me...