jetpack compose - Animation finished listener

MainActivity.kt

package com.cfsuman.jetpackcompose

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.activity.compose.setContent
import androidx.compose.animation.core.FastOutSlowInEasing
import androidx.compose.animation.core.animateFloatAsState
import androidx.compose.animation.core.tween
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.*
import androidx.compose.material.*
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.Favorite
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.alpha
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContent {
            MainContent()
        }
    }


    @Composable
    fun MainContent(){
        val isOpaque = remember { mutableStateOf(value = true) }
        val result = remember { mutableStateOf("")}

        val alpha: Float by animateFloatAsState(
            targetValue = if (isOpaque.value) 1f else 0.2f,
            animationSpec = tween(
                durationMillis = 3000, // animation duration
                easing = FastOutSlowInEasing // animation easing
            ),
            // animation finished listener
            finishedListener = {
                result.value = "Finished at $it"
            }
        )

        Column(
            modifier = Modifier
                .fillMaxSize()
                .background(Color(0xFFD9E650))
                .padding(16.dp),
            verticalArrangement = Arrangement.spacedBy(16.dp),
            horizontalAlignment = Alignment.CenterHorizontally
        ) {
            Button(
                onClick = { isOpaque.value = !isOpaque.value },
                colors = ButtonDefaults.buttonColors(
                    Color(0xFF4C9141), Color(0xCCFFFFFF)
                )
            ) {
                Text(text = "Animate Opacity")
            }

            Icon(
                Icons.Filled.Favorite,
                "Localized description",
                tint = Color(0xFFD92121),
                modifier = Modifier
                    .size(300.dp)
                    .alpha(alpha = alpha)
            )

            Text(
                text = result.value,
                fontSize = 25.sp,
                fontWeight = FontWeight.Bold
            )
        }
    }


    @Preview
    @Composable
    fun ComposablePreview(){
        //MainContent()
    }
}