Center in Coordinator visible area

CoordinatorCenterViewBehavior.kt

package com.master.accessibility.ui.mainactivity2

import android.content.Context
import android.support.design.widget.AppBarLayout
import android.support.design.widget.CoordinatorLayout
import android.util.AttributeSet
import android.view.View
import android.widget.ImageView

class CoordinatorCenterViewBehavior : CoordinatorLayout.Behavior<ImageView> {
    constructor() : super()
    constructor(context: Context?, attrs: AttributeSet?) : super(context, attrs)

    val LOG = "LOG"
    override fun layoutDependsOn(parent: CoordinatorLayout, child: ImageView, dependency: View): Boolean {
        if (dependency is AppBarLayout) {

            return true
        }
        return super.layoutDependsOn(parent, child, dependency)
    }

    override fun onDependentViewChanged(parent: CoordinatorLayout, child: ImageView, dependency: View): Boolean {
        if (dependency is AppBarLayout) {
            val visibleArea = (parent.height - dependency.bottom)
            val centerPosition = (visibleArea / 2) - (child.height / 2) + dependency.bottom
            child.x = (parent.width / 2 - child.width / 2).toFloat()
            child.y = centerPosition.toFloat()
            return true
        }
        return super.onDependentViewChanged(parent, child, dependency)
    }
}

gistfile1.txt

Used in case of viewpager
referenceView.addView(<your view inside viewpager fragments>)

ReferenceView.kt

package com.fanclips.common.util

import android.content.Context
import android.util.AttributeSet
import android.view.View
import android.widget.TextView

class ReferenceView : View {
    constructor(context: Context?) : super(context)
    constructor(context: Context?, attrs: AttributeSet?) : super(context, attrs)
    constructor(context: Context?, attrs: AttributeSet?, defStyleAttr: Int) : super(context, attrs, defStyleAttr)
    constructor(context: Context?, attrs: AttributeSet?, defStyleAttr: Int, defStyleRes: Int) : super(context, attrs, defStyleAttr, defStyleRes)

    val referenceViews = ArrayList<View>()
    fun addView(view: View) {
        var isFound = false
        if(referenceViews.isNotEmpty()) {
            for (i in 0..referenceViews.size) {
                if (referenceViews.get(i).id == view.id) {
                    isFound = true
                    break
                }
            }
        }
        if (!isFound) {
            referenceViews.add(view)
        }
    }
}