jetpack compose - Backdrop scaffold

MainActivity.kt

package com.cfsuman.jetpackcompose

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.activity.compose.setContent
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.*
import androidx.compose.material.*
import androidx.compose.runtime.*
import androidx.compose.ui.graphics.Color
import androidx.compose.material.Text
import androidx.compose.material.TopAppBar
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.Email
import androidx.compose.material.icons.filled.Favorite
import androidx.compose.material.icons.filled.Phone
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.vector.ImageVector
import androidx.compose.ui.unit.dp
import kotlinx.coroutines.launch


class MainActivity : AppCompatActivity() {
    override fun onCreate(savedObjectState: Bundle?) {
        super.onCreate(savedObjectState)
        setContent {
            GetScaffold()
        }
    }


    @OptIn(ExperimentalMaterialApi::class)
    @Composable
    fun GetScaffold(){
        val backdropScaffoldState = rememberBackdropScaffoldState(
            initialValue = BackdropValue.Concealed)
        val selectedIcon = remember {
            mutableStateOf(Icons.Filled.Favorite)}

        BackdropScaffold(
            scaffoldState = backdropScaffoldState,
            appBar = {
                TopAppBar(
                    title = { Text(
                        text = "Compose - Backdrop Scaffold"
                    )},
                    backgroundColor = Color(0xFF1ca9c9),
                )
            },
            backLayerContent = {BackLayerContent(
                backdropScaffoldState, selectedIcon
            )},
            frontLayerContent = { FrontLayerContent(
                backdropScaffoldState, selectedIcon) },
        )
    }


    @OptIn(ExperimentalMaterialApi::class)
    @Composable
    fun BackLayerContent(
        backdropScaffoldState: BackdropScaffoldState,
        selectedIcon: MutableState<ImageVector>
    ){
        val scope = rememberCoroutineScope()
        Box(
            modifier = Modifier.background(Color(0xFF5D8AA8))
                .fillMaxSize(),
            contentAlignment = Alignment.Center
        ) {
            Column(
                verticalArrangement = Arrangement.spacedBy(12.dp),
                horizontalAlignment = Alignment.CenterHorizontally
            ) {
                OutlinedButton(onClick = {
                    selectedIcon.value = Icons.Filled.Favorite
                    scope.launch {
                        backdropScaffoldState.conceal()
                    }
                }) {
                    Icon(Icons.Filled.Favorite, "")
                    Text(text = "Favorite")
                }

                OutlinedButton(onClick = {
                    selectedIcon.value = Icons.Filled.Email
                    scope.launch {
                        backdropScaffoldState.conceal()
                    }
                }) {
                    Icon(Icons.Filled.Email, "")
                    Text(text = "Email")
                }

                OutlinedButton(onClick = {
                    selectedIcon.value = Icons.Filled.Phone
                    scope.launch {
                        backdropScaffoldState.conceal()
                    }
                }) {
                    Icon(Icons.Filled.Phone, "")
                    Text(text = "Phone")
                }
            }
        }
    }
    
    
    @OptIn(ExperimentalMaterialApi::class)
    @Composable
    fun FrontLayerContent(
        backdropScaffoldState: BackdropScaffoldState,
        selectedIcon: MutableState<ImageVector>
    ){
        Box(
            modifier = Modifier.background(Color(0xFF89CFF0))
                .fillMaxSize(),
            contentAlignment = Alignment.Center
        ) {
            Column(
                horizontalAlignment = Alignment.CenterHorizontally,
                verticalArrangement = Arrangement.spacedBy(12.dp)
            ) {
                Icon(
                    selectedIcon.value,
                    contentDescription = "",
                    Modifier.size(250.dp),
                    tint = Color(0xFF002147)
                )
                Text(text = "Front layer content")
            }
        }
    }
}