ViewPager for Android (SDK 22) in Kotlin 1.0.2. It can be scrolled in one direction. (Left only, Right only or Both)

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <xxx.view.CustomViewPager
        android:id="@+id/main_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</RelativeLayout>

CustomViewPager.kt

package xxx.view

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

class CustomViewPager(context: Context, attrs: AttributeSet?) : ViewPager(context, attrs) {

    constructor(context: Context) : this(context, null)

    companion object {
        val SCROLL_PREV = 0b01  // Left
        val SCROLL_NEXT = 0b10  // Right
        val SCROLL_BOTH = SCROLL_NEXT + SCROLL_PREV
    }

    var scrollDirection = SCROLL_BOTH

    private var downX: Float? = null

    override fun onTouchEvent(ev: MotionEvent): Boolean =
            if (canScroll(ev)) super.onTouchEvent(ev) else false

    override fun onInterceptTouchEvent(ev: MotionEvent): Boolean =
            if (canScroll(ev)) super.onInterceptTouchEvent(ev) else false

    private fun canScroll(ev: MotionEvent): Boolean {
        if (ev.action == MotionEvent.ACTION_DOWN) {
            downX = ev.x
            return true
        }
        downX?.let {
            val diffX = ev.x - it
            if (diffX > 0 && scrollDirection.and(SCROLL_PREV) == 0) {
                return false
            }
            if (diffX < 0 && scrollDirection.and(SCROLL_NEXT) == 0) {
                return false
            }
        }
        return true
    }
}

MainActivity.kt

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        findViewById(R.id.main_container).let {
            it as CustomViewPager
            it.scrollDirection = CustomViewPager.SCROLL_PREV
            it.adapter = MainPagerAdapter(supportFragmentManager) // Plaese implement MainPagerAdapter
        }
    }
}