NestedScrollViewWithRecyclerView.kt

package tv.standard.ui.view.custom

import android.content.Context
import android.graphics.Rect
import android.util.AttributeSet
import android.view.View
import androidx.core.widget.NestedScrollView
import androidx.recyclerview.widget.LinearLayoutManager

const val TAG = "MyNestedScroll"

/**
 * Solution found here https://stackoverflow.com/questions/52218109/findlastvisibleitemposition-is-returning-wrong-value-if-recyclerview-inside-nest
 * to deal with a RecyclerView inside NestedScrollView
 */
class NestedScrollViewWithRecyclerView : NestedScrollView {
    private var screenHeight = 0
    private var isBottomOfList: IsBottomOfList? = null
    private var linearLayoutManager: LinearLayoutManager? = null

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

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

    constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int) : super(
        context,
        attrs,
        defStyleAttr
    ) {
        init()
    }

    private fun init() {
        screenHeight = context.resources.displayMetrics.heightPixels
    }

    override fun onScrollChanged(l: Int, t: Int, oldl: Int, oldt: Int) {
        super.onScrollChanged(l, t, oldl, oldt)
        isBottomOfList?.isBottomOfList(isVisible)
    }

    val isVisible: Boolean
        get() {
            val childCount = linearLayoutManager?.childCount ?: 0
            val view: View = linearLayoutManager?.getChildAt(childCount - 1) ?: return false
            if (!view.isShown) {
                return false
            }
            val actualPosition = Rect()
            view.getGlobalVisibleRect(actualPosition)
            val height1 = view.height
            val height2 = actualPosition.bottom - actualPosition.top
            return actualPosition.bottom < screenHeight && height1 == height2
        }

    fun setIsBottomOfList(isBottomOfList: IsBottomOfList?) {
        this.isBottomOfList = isBottomOfList
    }

    fun setLinearLayoutManager(linearLayoutManager: LinearLayoutManager?) {
        this.linearLayoutManager = linearLayoutManager
    }

    interface IsBottomOfList {
        fun isBottomOfList(isBottom: Boolean)
    }
}