Migrating from XML to Jetpack Compose: A Practical Strategy

Transitioning a production Android app from the traditional XML View system to Jetpack Compose is rarely a weekend project. For a small studio like AIA Innovations, where we maintain several focused productivity apps like Salah Companion and ShariahSignal, the primary challenge isn't just learning the new declarative syntax. The real hurdle is ensuring that the migration doesn't break existing features, degrade performance, or result in a fragmented user interface where half the app looks and feels different from the other. A total rewrite is often a luxury small teams cannot afford; instead, a systematic, modular approach to incremental modernization is the most reliable path forward.

The Case for Interoperability

Jetpack Compose was designed with interoperability as a core feature. You do not have to choose between XML and Compose for your entire project. The most successful migrations we have executed at our studio follow a "Compose in View" or "View in Compose" strategy.

For a modular app, the best entry point is often a new feature or a standalone screen. In ShariahSignal, for example, we might choose to build a new stock detail screen entirely in Compose while keeping the main dashboard in XML. This allows the team to build a robust design system in Compose without the pressure of rewriting legacy code that already works. By utilizing the ComposeView within an existing XML layout, you can embed a small Compose-based component—like a custom progress bar or a specific data visualization—directly into a legacy Fragment.

Establishing the Bridge: Theming and Design Systems

The most common pitfall in a hybrid transition is the "theme gap." Your XML-based Theme.AppCompat or Theme.MaterialComponents does not automatically translate to a Compose MaterialTheme. Before writing your first Composable, you must establish a bridge.

We recommend using the Google Accompanist themeadapter-material3 or themeadapter-appcompat libraries, which can parse your existing XML theme attributes and make them available to Compose. However, for long-term stability, we eventually move toward a shared DesignSystem module. This module defines your colors, typography, and shapes as plain Kotlin objects that both systems can reference.

A Step-by-Step Modular Strategy

#### 1. The Low-Stakes Component Phase Start by replacing small, isolated UI elements. In Salah Companion, this might be the individual row representing a prayer time. By rewriting just the row item in Compose and using a ComposeView inside your existing RecyclerView.ViewHolder, you can test the waters of performance and state management.

#### 2. The Leaf Screen Phase Once your basic components (buttons, text styles, input fields) are stable in Compose, identify "Leaf Screens." These are screens that do not have complex navigation sub-flows. A "Settings" screen or a "Stock Details" screen in ShariahSignal is an ideal candidate. Converting a whole screen allows you to remove the Fragment-XML binding overhead and move toward a cleaner ViewModel-to-UI state flow.

#### 3. The Navigation Hybrid Phase Navigation is where things get complex. If you are using the Jetpack Navigation Component, you can mix and match XML fragments and Compose destinations within the same navigation graph. We generally advise keeping the host Activity as the source of truth for navigation until at least 70% of the screens are migrated.

Managing State and Unidirectional Data Flow

Compose thrives on Unidirectional Data Flow (UDF). In the XML world, we often find ourselves manually setting values on views: textView.text = "Updated Value". In Compose, this is an anti-pattern.

When migrating, your ViewModels should already be exposing state via StateFlow or LiveData. If you have followed our advice in Implementing Local-Only Data, your data layer is likely already structured as a single source of truth. The migration then becomes a task of "observing" that state in a Composable using collectAsStateWithLifecycle().

Practical Example: Converting a Toggle Component

Consider a simple custom toggle used in a productivity app to enable/disable notifications.

Legacy XML Approach:

1. 1.Create res/layout/toggle_component.xml.
2. 2.Create a custom View class or use a SwitchCompat.
3. 3.In the Fragment, find the view by ID and set an onCheckedChangedListener.
4. 4.Manually update the view state when the ViewModel changes.

Compose Migration Approach: ``kotlin @Composable define NotificationToggle( isEnabled: Boolean, onToggle: (Boolean) -> Unit ) { Row(verticalAlignment = Alignment.CenterVertically) { Text("Enable Notifications") Switch( checked = isEnabled, onCheckedChange = onToggle ) } } ` You can now use this Composable in your legacy XML layout using ComposeView: `xml <androidx.compose.ui.platform.ComposeView android:id="@+id/compose_view" android:layout_width="match_parent" android:layout_height="wrap_content" /> ` In your Fragment: `kotlin binding.composeView.setContent { Mdc3Theme { // Adapts XML theme to Compose NotificationToggle(state.isEnabled) { viewModel.toggle(it) } } } ``

Performance Pitfalls to Watch For

During a hybrid transition, performance can actually take a temporary hit if not managed carefully. Every ComposeView instance in an XML layout adds a small amount of overhead. If you have a RecyclerView with 100 items and each item is a ComposeView, you may see scrolling stutter on lower-end devices.

To mitigate this, avoid frequent "re-composition" of the entire list. Ensure your data classes are @Immutable or @Stable so Compose knows it doesn't need to redraw them unless the properties actually change. We also recommend keeping your Compose version and Kotlin version strictly aligned with the compatibility map provided by Google to ensure the compiler optimizations are working correctly.

Why the Effort is Worth It

For a studio building focused tools, the speed of iteration is our greatest competitive advantage. In Mindful Assistant, which requires a highly polished, calm aesthetic, Compose allows us to build complex animations and custom transitions in a fraction of the time it would take in XML. The reduction in boilerplate code—no more findViewById, no more Synthetic bindings, and no more fragile XML-based StateListDrawables—means fewer bugs and a smaller APK size.

Migration Checklist

Before you start your next sprint, run through this checklist to ensure your migration strategy is sound:

• [ ] Dependency Audit: Are your minSdkVersion and Gradle version high enough to support the latest Compose compiler?
• [ ] Theme Bridge: Have you mapped your XML colorPrimary, colorSecondary, and typography to a MaterialTheme object?
• [ ] State Flow: Does your ViewModel expose a single UI state object, or are you still pushing data to views manually?
• [ ] Feature Selection: Have you identified a low-risk "leaf screen" or a new feature to serve as the pilot for Compose?
• [ ] Testing: Have you verified that your UI tests (Espresso or Compose Test Rule) can interact with the hybrid layout?

What to do next

1. 1.Map your theme: Create a Theme.kt file that uses themeadapter-material3 to ensure your existing XML styles carry over to your first Composable.
2. 2.Pick one component: Identify a single custom UI element in your app—like a specialized button or status badge—and rewrite it as a Composable, then inject it into its existing XML location using ComposeView.
3. 3.Refactor the state: Ensure the ViewModel for your target screen is using StateFlow to expose data, making it ready for a collectAsStateWithLifecycle() call in the UI layer.