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">

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

</RelativeLayout>

MainActivity.kt

class MainActivity : AppCompatActivity() {

    private fun updateViewPager() {
        findViewById(R.id.main_container).let {
            it as ViewPager
            (it.adapter as MainPagerAdapter).last = it.currentItem
        }
    }
}

MainPagerAdapter.kt

package xxx.view

import android.support.v4.app.Fragment
import android.support.v4.app.FragmentManager
import android.support.v4.app.FragmentPagerAdapter

class MainPagerAdapter(fm: FragmentManager) : FragmentPagerAdapter(fm) {

    private val fragments: MutableList<Fragment> = mutableListOf()

    var last: Int = 0
        set(last) {
            field = last
            notifyDataSetChanged()
        }

    fun addFragment(fragment: Fragment) = fragments.add(fragment)

    fun indexOf(fragment: Fragment): Int = fragments.indexOf(fragment)

    override fun getCount(): Int = if (last < fragments.size) last + 1 else 0

    override fun getItem(position: Int): Fragment? = fragments[position]
}