Question 127759 in Android Studio Question posted in
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Android Studio – How can I preview a Compose view when it need a parameter in Android Studio?

I can run Code A in Android Studio, I hope to preview UI when I’m designing, so I added Code B to Code A.

But Code B can’t work, why? How can I fix it?

Code A

class MainActivity : ComponentActivity() {

    private val handleMeter by viewModels<HandleMeter>()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            SoundMeterTheme {       
                Surface(color = MaterialTheme.colors.background) {
                    Greeting(handleMeter)
                }
            }
        }
    }
}

@Composable
fun Greeting(handleMeter: HandleMeter) {
  ...
}

Code B

@Preview(showBackground = true)
@Composable
fun DefaultPreview() {
    SoundMeterTheme {
        val handleMeter by viewModels<HandleMeter>()
        Greeting(handleMeter)
    }
}
Tags:

2

Answers


  1. 0

    Unfortunately, you can’t.
    Preview does not support creating ViewModels and NavHost yet, for our bad.
    But what you can do instead is to use a fake data or a static data into ui, until the design finish and when you are ready to actually run it, replace the static data with the view model data.

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  2. 0

    You can use dagger and hilt to inject the view model constructor and then call up the hilt view model in the preview e.g.

    @HiltViewModel
class DataFieldsViewModel @Inject constructor(
) : ViewModel() {

    Then in your preview code for your composable

    @Preview(showBackground = true)
@Composable
fun PreviewDataFieldsScreen() {
    DataFieldsScreen(
        navController = rememberNavController(),
        viewModel = hiltViewModel()
    )
}
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