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

I've been doing similar things, but for horizontal swipes only

import android.content.Context
import android.view.GestureDetector
import android.view.MotionEvent
import android.view.View

abstract class OnHorizontalSwipeListener(val context: Context) : View.OnTouchListener {    

    companion object {
         const val SWIPE_MIN = 50
         const val SWIPE_VELOCITY_MIN = 100
    }

    private val detector = GestureDetector(context, GestureListener())

    override fun onTouch(view: View, event: MotionEvent) = detector.onTouchEvent(event)    

    abstract fun onRightSwipe()

    abstract fun onLeftSwipe()

    private inner class GestureListener : GestureDetector.SimpleOnGestureListener() {    

        override fun onDown(e: MotionEvent) = true

        override fun onFling(e1: MotionEvent, e2: MotionEvent, velocityX: Float, velocityY: Float)
            : Boolean {

            val deltaY = e2.y - e1.y
            val deltaX = e2.x - e1.x

            if (Math.abs(deltaX) < Math.abs(deltaY)) return false

            if (Math.abs(deltaX) < SWIPE_MIN
                    && Math.abs(velocityX) < SWIPE_VELOCITY_MIN) return false

            if (deltaX > 0) onRightSwipe() else onLeftSwipe()

            return true
        }
    }
}

And then it can be used for view components

private fun listenHorizontalSwipe(view: View) {
    view.setOnTouchListener(object : OnHorizontalSwipeListener(context!!) {
            override fun onRightSwipe() {
                Log.d(TAG, "Swipe right")
            }

            override fun onLeftSwipe() {
                Log.d(TAG, "Swipe left")
            }

        }
    )
}