CollapsingHeaderView

collapsing_header_view.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/app_bar_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:fitsSystemWindows="true">

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collapsing_toolbar"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_scrollFlags="scroll|exitUntilCollapsed"
            android:fitsSystemWindows="true"
            app:contentScrim="@android:color/transparent">

            <FrameLayout
                android:id="@+id/collapsing_header_view_top"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                app:layout_collapseMode="none"/>

        </android.support.design.widget.CollapsingToolbarLayout>

    </android.support.design.widget.AppBarLayout>

    <FrameLayout
        android:id="@+id/collapsing_header_view_bottom"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:clipToPadding="false"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"/>

    <FrameLayout
        android:id="@+id/collapsing_header_view_divider"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:visibility="gone"
        app:layout_anchor="@id/collapsing_header_view_bottom"
        app:layout_anchorGravity="top"
        app:layout_collapseMode="none"/>

</android.support.design.widget.CoordinatorLayout>

CollapsingHeaderView.kt

package com.savrov.collapsingheaderview

import android.annotation.SuppressLint
import android.content.Context
import android.support.design.widget.AppBarLayout
import android.support.design.widget.CollapsingToolbarLayout
import android.support.design.widget.CoordinatorLayout
import android.support.v4.app.Fragment
import android.support.v7.widget.RecyclerView
import android.util.AttributeSet
import android.util.Log
import android.view.View
import android.widget.FrameLayout
import android.opengl.ETC1.getHeight
import android.view.ViewTreeObserver
import android.R.attr.data
import android.util.TypedValue
import android.view.ViewGroup
import android.widget.LinearLayout


@SuppressLint("LongLogTag")
class CollapsingHeaderView : CoordinatorLayout {

    companion object {
        private const val TAG = "CollapsingHeaderView::class"
    }

    lateinit var view: View
    lateinit var viewTop: FrameLayout
    lateinit var viewBottom: FrameLayout
    lateinit var viewDivider: FrameLayout

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

    constructor(context: Context, attributeSet: AttributeSet): super(context, attributeSet) {
        init(context, attributeSet)
    }

    private fun init(context: Context, attributeSet: AttributeSet? = null) {
        view = inflate(context, R.layout.collapsing_header_view, this)
        viewTop = view.findViewById<FrameLayout>(R.id.collapsing_header_view_top)
        viewDivider = view.findViewById<FrameLayout>(R.id.collapsing_header_view_divider)
        viewBottom = view.findViewById<FrameLayout>(R.id.collapsing_header_view_bottom)
    }

    fun addViewTop(top: View) {
        viewTop.addView(top)
    }

    fun addViewBottom(bottom: View) {
        viewBottom.addView(bottom)
    }

    fun addViewDivider(divider: View) {
        viewDivider.apply {
            addView(divider)
            visibility = View.VISIBLE
            viewTreeObserver.addOnGlobalLayoutListener(object: ViewTreeObserver.OnGlobalLayoutListener {
                override fun onGlobalLayout() {
                    viewDivider.viewTreeObserver.removeOnGlobalLayoutListener(this)
                    val bottomParams = viewBottom.layoutParams as MarginLayoutParams
                    bottomParams.topMargin = viewDivider.height/2
                    viewBottom.apply {
                        layoutParams = bottomParams
                        setPadding(0, viewDivider.height/2, 0, 0)
                        requestLayout()
                        invalidate()
                    }

                }
            })
        }
    }

    fun setViewTopScrollFlags(scrollFlags: Int) {
        val collapsingToolbar = view.findViewById<CollapsingToolbarLayout>(R.id.collapsing_toolbar)
        val params = collapsingToolbar.layoutParams as AppBarLayout.LayoutParams
        params.scrollFlags = scrollFlags
        collapsingToolbar.layoutParams = params
    }

}