Performance Truth: AOT vs JIT

Controversy about Compose performance never stops. Benchmarks show that Compose is often slower than XML for initial page loads (startup time). This is because XML Views are part of the Android system framework, starting with the system and AOT (Ahead-of-Time) pre-compiled during installation. Compose, as a decoupled library packaged in the APK, requires JIT (Just-in-Time) compilation and class loading on first run, bringing a "one-time cost."

However, this doesn't mean Compose is slow. By introducing "Baseline Profiles," developers can instruct the system to AOT compile critical Compose paths during installation, almost completely eliminating startup performance gaps.

In runtime performance (such as list scrolling, animation smoothness), thanks to smart recomposition mechanisms, Compose often outperforms traditional View systems, showing lower frame drop rates (Slow Frame %).

Authoritative Migration Strategy: Step by Step

For large XML projects, "rewriting" is unacceptable. The officially recommended and only viable strategy is "incremental migration."

1. **Use Compose for new features**: All new screens and feature modules should be 100% Compose.

2. **Build a Design System**: Extract common UI components (buttons, inputs, cards) as Compose components to establish a unified design system.

3. **Migrate screen by screen**: Start with simple pages and gradually replace existing Activities or Fragments.

Interoperability Tactical Manual

**Using Compose in XML**: Use `ComposeView`. The key is setting `setViewCompositionStrategy(ViewCompositionStrategy.DisposeOnViewTreeLifecycleDestroyed)` to ensure Compose state is properly cleaned when Fragment views are destroyed, avoiding memory leaks and state loss.

**Using XML in Compose**: Use `AndroidView`. This is the bridge for integrating maps, WebViews, or complex custom Views that haven't been migrated yet. Create Views through the `factory` lambda and respond to Compose state changes through the `update` lambda for a unidirectional data flow closed loop.

@Composable
fun LegacyMapComponent(lat: Double, lng: Double) {
    AndroidView(
        factory = { context ->
            MapView(context).apply {
                onCreate(null)
                getMapAsync { /* init */ }
            }
        },
        update = { view ->
            // When lat/lng changes, update MapView
            view.updateLocation(lat, lng)
        }
    )
}