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

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

/**
 * Detects left and right swipes across a view.
 */
class OnSwipeTouchListener(context: Context, onSwipeCallBack: OnSwipeCallBack?) : OnTouchListener {

    private var gestureDetector : GestureDetector
    private var onSwipeCallBack: OnSwipeCallBack?=null

    init {

        gestureDetector = GestureDetector(context, GestureListener())
        this.onSwipeCallBack = onSwipeCallBack!!
    }
    companion object {

        private val SWIPE_DISTANCE_THRESHOLD = 100
        private val SWIPE_VELOCITY_THRESHOLD = 100
    }

   /* fun onSwipeLeft() {}

    fun onSwipeRight() {}*/

    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(eve1: MotionEvent?, eve2: MotionEvent?, velocityX: Float, velocityY: Float): Boolean {
            try {
                if(eve1 != null&& eve2!= null) {
                    val distanceX = eve2?.x - eve1?.x
                    val distanceY = eve2?.y - eve1?.y
                    if (Math.abs(distanceX) > Math.abs(distanceY) && Math.abs(distanceX) > SWIPE_DISTANCE_THRESHOLD && Math.abs(velocityX) > SWIPE_VELOCITY_THRESHOLD) {
                        if (distanceX > 0)
                            onSwipeCallBack!!.onSwipeLeftCallback()
                        else
                            onSwipeCallBack!!.onSwipeRightCallback()
                        return true
                    }
                }
            }catch (exception:Exception){
                exception.printStackTrace()
            }

            return false
        }


    }
}