Jetpack Compose Dark Theme Main Activity

MainActivity.kt

class MainActivity : ComponentActivity() {
    private val themeViewModel: ThemeViewModel by viewModels()
    private lateinit var dataStoreUtil: DataStoreUtil

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

        dataStoreUtil = DataStoreUtil(applicationContext)

        //Checks if the system theme is DarkMode or not.
        val systemTheme = when (resources.configuration.uiMode and Configuration.UI_MODE_NIGHT_MASK) {
            Configuration.UI_MODE_NIGHT_YES -> { true }
            Configuration.UI_MODE_NIGHT_NO -> { false }
            else -> { false }
        }

        setContent {
            val theme = dataStoreUtil.getTheme(systemTheme).collectAsState(initial = systemTheme)

            JetpackComposeDarkThemeTheme(
                darkTheme = theme.value,
            ) {
                Surface(
                    modifier = Modifier.fillMaxSize(),
                    color = MaterialTheme.colorScheme.background,
                ) {
                    DarkThemeScreen(dataStoreUtil, themeViewModel)
                }
            }
        }
    }
}

@OptIn(ExperimentalMaterial3Api::class)
@SuppressLint("UnusedMaterial3ScaffoldPaddingParameter")
@Composable
fun DarkThemeScreen(
    dataStoreUtil: DataStoreUtil,
    themeViewModel: ThemeViewModel,
) {
    var switchState by remember {themeViewModel.isDarkThemeEnabled }
    val coroutineScope = rememberCoroutineScope()

    Scaffold(
        //...
    ) {
        Column(
            //...
        ) {
            //...
            
            Switch(
                checked = switchState,
                onCheckedChange = {
                    switchState = it

                    coroutineScope.launch {
                        dataStoreUtil.saveTheme(it)
                    }
                },
                thumbContent = {
                    Icon(
                        modifier = Modifier
                            .size(SwitchDefaults.IconSize),
                        imageVector = if (switchState) Icons.Rounded.DarkMode else Icons.Rounded.LightMode,
                        contentDescription = ""
                    )
                },
                colors = SwitchDefaults.colors(
                    checkedTrackColor = MaterialTheme.colorScheme.primary,
                    checkedThumbColor = MaterialTheme.colorScheme.onPrimary,
                ),
            )
        }
    }
}