我有一个首选项列表,我循环它以创建一个设置屏幕,我想保存每个项目的状态,但当我重新启动应用程序时它不会保存状态
每个功能切换的代码:
@Composable
private fun FunctionToggle(name: String, desc: String, id: String) {
val context = LocalContext.current
val scope = rememberCoroutineScope()
val ds = DataStoreKeys(context)
val currentState = ds.getDataStoreValue(id).collectAsState(initial = false).value
var checked by rememberSaveable { mutableStateOf(currentState) }
ListItem(
modifier = Modifier.padding(vertical = 4.dp),
headlineContent = {
Text(
text = name,
style = MaterialTheme.typography.titleLarge,
)
},
supportingContent = {
Text(
text = desc,
style = MaterialTheme.typography.bodyMedium,
)
},
trailingContent = {
Switch(
checked = checked == true,
onCheckedChange = {
checked = it
scope.launch {
ds.saveToDataStore(key = id, value = it)
}
},
)
},
)
class DataStoreKeys(private val context: Context) {
companion object {
private val Context.dataStore: DataStore<Preferences> by preferencesDataStore("userSettings")
}
fun getDataStoreValue(key: String): Flow<Boolean?> {
return context.dataStore.data.map { preferences ->
preferences[booleanPreferencesKey(key)] ?: false
}
}
suspend fun saveToDataStore(key: String, value: Boolean) {
context.dataStore.edit { preferences ->
preferences[booleanPreferencesKey(key)] = value
}
}
}
问题就在这里:
val currentState = ds.getDataStoreValue(id).collectAsState(initial = false).value
var checked by rememberSaveable { mutableStateOf(currentState) }
您正在使用默认值
false
从数据存储中收集流量,然后记住 checked
变量中的值。问题是,当 checked
更改时,您不会更新 currentState
,因此它始终保持默认值(直到您直接从 switch 回调中更改它)。
根据我的经验,数据存储更新足够快,因此您实际上不需要额外的
checked
变量,您可以直接使用数据存储中的值。如果您仍然希望直接更改 switch 回调中的值,您可以执行以下操作:
var checked by remember { mutableStateOf(false) }
LaunchedEffect(Unit) {
ds.getDataStoreValue(id).collect { checked = it }
}
Switch(
checked = checked,
onCheckedChange = {
checked = it
scope.launch {
ds.saveToDataStore(key = id, value = it)
}
},
)
这样,每次数据存储有新值时,
checked
都会更新。