Android Jetpack Compose

Android Jetpack Compose Excellence 🎨

Expert guidance for building modern, high-performance Android UI with Jetpack Compose.

⚡ When to Use

• New Feature UI: Starting a new screen or custom component.
• UI Refactoring: Moving from XML to Compose or legacy Compose to modern patterns.
• Theming: Implementing Material 3, Dark Mode, or Custom Design Systems.
• Performance Fixes: Debugging recomposition issues or laggy lists.
• Animations: Adding smooth transitions and micro-interactions.

🏗️ Core Principles

1. State Management (Hoisting)

• Rule: Composables should be stateless where possible. Hoist state to the caller.
• Bad:

  @Composable
  fun SearchBar() {
      val text = remember { mutableStateOf("") } // Local state in reusable component
      TextField(value = text.value, text.value = it })
  }
  

• Good:

  @Composable
  fun SearchBar(
      query: String,
      onQueryChange: (String) -> Unit
  ) {
      TextField(value = query,
  }
  

2. Slot API Pattern

• For complex components, use "Slots" (content parameters) to increase flexibility.

  @Composable
  fun AppHeader(
      title: @Composable () -> Unit,
      actions: @Composable RowScope.() -> Unit = {}
  ) { ... }
  

3. Material 3 (M3)

• Always prefer androidx.compose.material3 components.
• Use ColorScheme, Typography, and Shapes from the theme.

🚀 Performance Checklist

• Lambda Stability: Method references (::onAction) or bound lambdas (val -> action(val)) are safer for stability than capturing unstable variables.
• derivedStateOf: Use when a state depends on another state that changes frequently (e.g., scroll position).
• remember(key): Correctly keying remember blocks to avoid stale data.
• Lists: Use LazyColumn / LazyRow and ALWAYS provide a key to items.

🎨 Animations

• AnimatedVisibility: For simple appear/disappear.
• animateColorAsState: For smooth color changes.
• Transition: For complex, multi-state animations.
• Lottie: Use lottie-compose for complex vector animations.

🧪 Testing and Previews

• Previews: Use @Preview(showBackground = true, uiMode = Configuration.UI_MODE_NIGHT_YES) for dark mode testing.
• Multi-device Previews: Use @PreviewScreenSizes and @PreviewFontScales.
• UI Testing: Use createComposeRule() and onNodeWithTag().

🔗 Related Resources

• Google Official Compose Samples
• Clean Architecture Skill