jetpack compose - Indeterminate LinearProgressIndicator

MainActivity.kt

package com.cfsuman.jetpackcompose

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.os.Handler
import android.os.Looper
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.*
import androidx.compose.material.*
import androidx.compose.runtime.Composable
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
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 isVisible = remember { mutableStateOf(false) }
        val isEnable = remember { mutableStateOf(true) }
        val result = remember { mutableStateOf("") }

        val handler = Handler(Looper.getMainLooper())

        Column(
            modifier = Modifier
                .padding(16.dp)
                .fillMaxWidth(),
            horizontalAlignment = Alignment.CenterHorizontally
        ) {
            Button(
                onClick = {
                    isVisible.value = true
                    isEnable.value = false
                    result.value = "File downloading...."

                    Thread {
                        Thread.sleep(10 * 1000)

                        handler.post {
                            isVisible.value = false
                            result.value = "Download finished."
                            isEnable.value = true
                        }
                    }.start()
                },
                enabled = isEnable.value
            ) {
                Text(text = "Download File")
            }

            Spacer(modifier = Modifier.requiredHeight(16.dp))
            if (isVisible.value){
                LinearProgressIndicator(
                    modifier = Modifier.fillMaxWidth(0.8f),
                )
            }

            Spacer(modifier = Modifier.requiredHeight(16.dp))
            Text(
                text = result.value,
                fontSize = 20.sp
            )
        }
    }


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