I have a ViewModel which uses Flow to get a Note object from my Room database:

var uiState by mutableStateOf(NoteUiState())
        private set


    private fun getNoteById(argument: Int) {
        viewModelScope.launch {
            try {
                repository.getNoteById(argument).collect { note ->
                    uiState = NoteUiState(note = note)
                }
            } catch (e: Exception) {
                uiState = NoteUiState(error = true)
            }
        }
    }

Note class:

@Entity(tableName = "notes")
data class Note(
    @PrimaryKey(autoGenerate = true) val id: Int = 0,
    @ColumnInfo(name = "title") val title: String = "",
    @ColumnInfo(name = "text") val text: String = "",
) {
    override fun toString() = title
}

This approach works fine, until I try to make a mutable strings with the values of the Note object as their default so I can update 2 TextField composables:

@OptIn(ExperimentalMaterial3Api::class)
@Composable
private fun Note(
    note: DataNote,
    isNewNote: Boolean,
    createNote: (DataNote) -> Unit,
    updateNote: (DataNote) -> Unit,
    back: () -> Unit,
    trued: String,
) {

    var title by remember { mutableStateOf(note.title) }
    var content by remember { mutableStateOf(note.text) }
    TextField(
        value = title,
        onValueChange = { title = it },
        modifier = Modifier
            .fillMaxWidth(),
        placeholder = { Text(text = "Title") },
        colors = TextFieldDefaults.textFieldColors(
            containerColor = Color.Transparent
        )
    )
    TextField(
        value = content,
        onValueChange = { content = it },
        modifier = Modifier
            .fillMaxWidth(),
        placeholder = { Text(text = "Content") },
        colors = TextFieldDefaults.textFieldColors(
            containerColor = Color.Transparent
        )
    )
}

For some reason the first time the Note object is called it's null, so I want a way to update the title and content variables.

The Note object itself updates without issue, however the title and content variables never change from the initial value. How can I update the title and content variables while also making them work for the textfield?

CodePudding user response：

use SideEffect to update title and content

CodePudding user response：

 var title by remember { mutableStateOf(note.title) }
    var content by remember { mutableStateOf(note.text) }

remember block executes only on 1st composition and then value will remembered until decomposition or u need to change it externally through '=' assignment operator,

.

instated of this

TextField(
        value = title)

write this way

 TextField(
            value = note.title)