Stop Writing 20 @Preview Functions — Build a Runtime Sandbox Instead

#android #kotlin #jetpackcompose #mobile

Every Compose developer hits this wall eventually. You start with one @Preview. Then one for dark mode. Then one for large fonts. Then one per locale. Before you know it, you're scrolling through two dozen nearly-identical functions just to check whether a button label wraps in German.

The real problem isn't laziness — it's that static previews don't scale. Dark × 3 locales × 4 font scales × RTL is 24 permutations for a single screen. And your IDE renders all of them every build.

So I built PreviewSandbox. Instead of multiplying preview functions, you get an interactive control panel that lets you toggle every configuration axis at runtime — no rebuilds, no system-setting changes.

What It Looks Like

The API is intentionally minimal:

@Preview
@Composable
private fun ScreenPreview() {
    PreviewSandbox(
        theme = { state, content ->
            AppTheme(darkTheme = state.isDark) { content() }
        }
    ) {
        MyScreen()
    }
}