A Custom ViewPager for Android with an option to make it swipe to left only, swipe to right only or completely disbale the swipe

CustomSwipeableViewPager.java

import android.content.Context;
import android.support.v4.view.GestureDetectorCompat;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;

public class CustomSwipeableViewPager extends ViewPager {
    private static final String TAG = "CustomSwipeableViewPager";

    private static final float MIN_SWIPE_DISTANCE = 30.0f;

    public static enum SwipeType {
        DISABLED, TO_LEFT, TO_RIGHT, ENABLED
    }

    private SwipeType mSwipeType;
    private GestureDetectorCompat mGestureDetector;

    public CustomViewPager(Context context) {
        super(context);

        myInitViewPager();
    }

    public CustomViewPager(Context context, AttributeSet attrs) {
        super(context, attrs);

        myInitViewPager();
    }

    private void myInitViewPager() {
        mSwipeType = SwipeType.ENABLED;

        mGestureDetector = new GestureDetectorCompat(getContext(), simpleOnGestureListener);
        mGestureDetector.setIsLongpressEnabled(true);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (mSwipeType) {
            case DISABLED:
                return false;

            case ENABLED:
                return super.onTouchEvent(event);

            default:
                return mGestureDetector.onTouchEvent(event) && super.onTouchEvent(event);
        }
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent event) {
        switch (mSwipeType) {
            case DISABLED:
                return false;

            default:
                return super.onInterceptTouchEvent(event);
        }
    }

    public void setSwipeType(SwipeType swipeType) {
        mSwipeType = swipeType;
    }

    private GestureDetector.SimpleOnGestureListener simpleOnGestureListener = new GestureDetector.SimpleOnGestureListener() {

        @Override
        public boolean onDown(MotionEvent e) {
            return true;
        }

        @Override
        public boolean onSingleTapConfirmed(MotionEvent e) {
            return true;
        }

        @Override
        public boolean onSingleTapUp(MotionEvent e) {
            return true;
        }

        @Override
        public boolean onDoubleTap(MotionEvent e) {
            return true;
        }

        @Override
        public boolean onDoubleTapEvent(MotionEvent e) {
            return true;
        }

        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
            return true;
        }

        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
            final float diffX = e2.getX() - e1.getX();
            if (Math.abs(diffX) < MIN_SWIPE_DISTANCE) {
                return true;
            }

            if (diffX > 0) {
                // Swipe to Left
                return SwipeType.TO_LEFT == mSwipeType;
            } else {
                // Swipe to Right
                return SwipeType.TO_RIGHT == mSwipeType;
            }
        }
    };
}

It dos not working (((
line 102 e1 and e2 always null

I fix some errors and post here working example if some body will need to use it

typealias OnSwipeLeft = (position: Int?) -> Unit
typealias OnSwipeRight = (position: Int?) -> Unit
typealias OnSwipe = (position: Int?) -> Unit

class ViewPagerXX : ViewPager {
private var mSwipeType: SwipeType? = null
private var mGestureDetector: GestureDetectorCompat? = null
private var flag = false
private var currentPage = 0
var onSwipeLeft: OnSwipeLeft? = null
var onSwipeRight: OnSwipeRight? = null
var onSwipe: OnSwipe? = null
var event: MotionEvent? = null

constructor(context: Context?) : super(context!!) {
    init()
}

constructor(context: Context?, attrs: AttributeSet?) : super(
    context!!, attrs
) {
    init()
}

fun init() {
    mSwipeType = SwipeType.ENABLED
    mGestureDetector = GestureDetectorCompat(this.context, simpleOnGestureListener)
    mGestureDetector!!.setIsLongpressEnabled(true)
}

override fun onPageScrolled(position: Int, offset: Float, offsetPixels: Int) {
    currentPage = position
    super.onPageScrolled(position, offset, offsetPixels)
}

override fun onInterceptTouchEvent(ev: MotionEvent?): Boolean {
    var isAllowed = mGestureDetector!!.onTouchEvent(ev)
    return when (mSwipeType) {
        SwipeType.DISABLED -> false
        else -> if (isAllowed) super.onInterceptTouchEvent(ev) else flag
    }
}

fun setSwipeType(swipeType: SwipeType?) {
    mSwipeType = swipeType
}

private val simpleOnGestureListener: GestureDetector.SimpleOnGestureListener =
    object : GestureDetector.SimpleOnGestureListener() {

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

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

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

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

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

        override fun onFling(
            e1: MotionEvent?,
            e2: MotionEvent?,
            velocityX: Float,
            velocityY: Float
        ): Boolean {
            return true
        }

        override fun onScroll(
            e1: MotionEvent?,
            e2: MotionEvent?,
            distanceX: Float,
            distanceY: Float
        ): Boolean {
            if (e1 != null && e2 != null) {
                val diffX = e2.x - e1.x
                if (abs(diffX) < MIN_SWIPE_DISTANCE) {
                    return true
                }
                return if (diffX > 0) {
                    // Swipe to Left
                    onSwipe?.invoke(this@ViewPagerXX.currentItem)
                    onSwipeLeft?.invoke(this@ViewPagerXX.currentItem)
                    SwipeType.TO_LEFT == mSwipeType
                } else {
                    // Swipe to Right
                    onSwipe?.invoke(this@ViewPagerXX.currentItem)
                    onSwipeRight?.invoke(this@ViewPagerXX.currentItem)
                    SwipeType.TO_RIGHT == mSwipeType
                }
            } else {
                Log.d("EventState", "NULL")
                return false
            }
        }

    }


enum class SwipeType {
    DISABLED, TO_LEFT, TO_RIGHT, ENABLED
}
companion object {
    private const val MIN_SWIPE_DISTANCE = 30.0f
}

}