Resize viewgroup height when swiping over it

Activity.kt

package com.dertyp7214.experimantaltests

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import /*package*/.dp
import /*package*/.resetHeight
import /*package*/.resizeOnTouch

class Activity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(/*layout*/)

        viewGroup.resizeOnTouch(minHeight = 50.dp(this))
    }

    override fun onBackPressed() {
        viewGroup.resetHeight(50.dp(this))
    }
}

Int.kt

import android.content.Context

fun Int.dp(context: Context): Int {
    val scale = context.resources.displayMetrics.density
    return (this * scale + 0.5f).toInt()
}

View.kt

import android.transition.ChangeBounds
import android.transition.TransitionManager
import android.view.MotionEvent.ACTION_DOWN
import android.view.MotionEvent.ACTION_MOVE
import android.view.ViewGroup
import android.view.animation.AccelerateDecelerateInterpolator

fun ViewGroup.resizeOnTouch(
        remove: Boolean = false,
        tolerance: Int = -1,
        minHeight: Int = -1,
        maxHeight: Int = -1
) {
    var allowMove = false
    if (remove) setOnTouchListener { _, _ -> true }
    else setOnTouchListener { _, event ->
        val y = event.y

        when (event.action) {
            ACTION_DOWN -> {
                allowMove = tolerance == -1 || (y >= layoutParams.height - tolerance && y <= layoutParams.height + tolerance)
            }
            ACTION_MOVE -> {
                if (allowMove) {
                    layoutParams.height = if (minHeight != -1 && y < minHeight) minHeight else {
                        if (maxHeight != -1 && y > maxHeight) maxHeight else {
                            val parentHeight = (parent as ViewGroup).height
                            if (y > parentHeight && parentHeight != -1) parentHeight
                            else y.toInt()
                        }
                    }
                    requestLayout()
                }
            }
        }
        true
    }
}

val ViewGroup.isMaxHeight: Boolean
    get() = (parent as ViewGroup).height == layoutParams.height

fun ViewGroup.resetHeight(height: Int) {
    ChangeBounds().apply {
        startDelay = 0
        interpolator = AccelerateDecelerateInterpolator()
        duration = resources.getInteger(android.R.integer.config_longAnimTime).toLong()
        TransitionManager.beginDelayedTransition(this@resetHeight, this)
    }
    layoutParams.height = height
    requestLayout()
}