jetpack compose - Tween animation

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.*
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.AddAlarm
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 isEnabled = remember { mutableStateOf(true)}

        val alpha: Float by animateFloatAsState(
            targetValue = if (isOpaque.value) 1f else 0.3f,

            // tween animates between start and end values.
            // It specified duration and using an easing curve.
            animationSpec = tween(
                durationMillis = 1000, // animation duration
                easing = FastOutLinearInEasing // animation easing
            ),
            // animation finished listener
            finishedListener = {
                result.value = "Finished at alpha $it"
                isEnabled.value = true
            }
        )

        Column(
            modifier = Modifier
                .fillMaxSize()
                .background(Color(0xFF8F9779))
                .padding(16.dp),
            verticalArrangement = Arrangement.spacedBy(16.dp),
            horizontalAlignment = Alignment.CenterHorizontally
        ) {
            Button(
                onClick = {
                            isOpaque.value = !isOpaque.value
                            isEnabled.value = false
                          },
                colors = ButtonDefaults.buttonColors(
                    Color(0xFF4B5320), Color(0xCCFFFFFF)
                ),
                enabled = isEnabled.value
            ) {
                Text(
                    text = "Animate Opacity",
                    modifier = Modifier.padding(12.dp)
                )
            }

            Icon(
                Icons.Filled.AddAlarm,
                "Localized description",
                tint = Color(0xFF3D0C02),
                modifier = Modifier
                    .size(300.dp)
                    .alpha(alpha = alpha)
            )

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


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