相关疑难解决方法(0)

我正在尝试通过进行数字增量来将ViewModel与 Jetpack Compose 结合使用。

它不起作用。也许我没有以正确的方式使用 ViewModel。

这是我的活动代码：

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            Greeting()
        }
    }
}

@Composable
fun Greeting(
    helloViewModel: ViewModel = viewModel()
) {
    Column(
        verticalArrangement = Arrangement.Center,
        horizontalAlignment = Alignment.CenterHorizontally,
        modifier = Modifier.fillMaxSize()
    ) {
        Text(
            text = helloViewModel.number.toString(),
            fontSize = 60.sp,
            fontWeight = FontWeight.Bold
        )
        Button(onClick = { helloViewModel.addNumber() }) {
            Text(text = "Increment Number ${helloViewModel.number}")
        }

    }
}

@Preview(showBackground = true)
@Composable
fun DefaultPreview() {
    AppTheme { …

我正在为我的应用程序开发购物车功能。我希望分别添加/减少 LazyColumn 中每个列表项的数量。我只使用一个“记住”，因此如果我单击添加/减少，它们都会同时更新。如何单独控制每个项目？

截屏

@Composable
fun InventoryCartScreen(
    mainViewModel: MainViewModel = hiltViewModel()
) {

    val multiSelectValue = mutableStateOf(0)// This is the value I want to change

//random list
val shopList = listOf(
        ShoppingList(id = 0,itemNumber = "1",itemDescription = "1",currentInventory = 0,optimalInventory = 0,minInventory = 0),
        ShoppingList(id = 0,itemNumber = "2",itemDescription = "2",currentInventory = 0,optimalInventory = 0,minInventory = 0)
    )

    Column(...) {
       LazyColumn(...) {
            items(items = shopList, key = { it.id }) { item ->
                InventoryCartScreenContents(
                    onaddClick= { multiSelectValue.value ++ }, //adds …