ViewpagerHeader.kt

package com.google.androidstudio.motionlayoutexample.utils

import android.content.Context
import android.support.constraint.motion.MotionLayout
import android.support.v4.view.ViewPager
import android.util.AttributeSet

class ViewpagerHeader @JvmOverloads constructor(
        context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0
) : MotionLayout(context, attrs, defStyleAttr), ViewPager.OnPageChangeListener {

    override fun onPageScrollStateChanged(state: Int) {
    }

    override fun onPageScrolled(position: Int, positionOffset: Float, positionOffsetPixels: Int) {
        var numPages = 3
        progress = (position + positionOffset) / (numPages - 1)
    }

    override fun onPageSelected(position: Int) {
    }
}