JetpackCompose @PreviewParameter causes preview to disappear

Question

I've been exploring Jetpack Compose lately and discovered this very weird scenario where my @Preview is not showing and Android Studio is literally showing blank empty. No warnings or errors are shown.

This happens when I add @PreviewParameter to my composable function parameter.

Answer 1

The stupid solution was… It turns out that I had my PreviewParameterProvider declared in private and turning it to public or simply removing the visibility modifier fixed it.

class MyProvider : PreviewParameterProvider<MyClass> {
    ...
}

This wasn't even documented.

I hope Google will make it clear in the documentation or at least give an error in Android Studio so developers won't encounter this frustrating and time-wasting scenario.

Answer 2

I had another issue causing the same behaviour.

blank screen

@Preview
@Composable
fun MyComposablePreview(
    @PreviewParameter(MyComposableStateProvider::class) state: MyComposableState
) = MyComposable(state)

works

@Preview
@Composable
fun MyComposablePreview(
    @PreviewParameter(MyComposableStateProvider::class) state: MyComposableState
) {
  MyComposable(state)
}