Mobile Android Design

# Android Mobile Design

Master Material Design 3 (Material You) and Jetpack Compose to build modern, adaptive Android applications that integrate seamlessly with the Android ecosystem.

## When to Use This Skill

- Designing Android app interfaces following Material Design 3
- Building Jetpack Compose UI and layouts
- Implementing Android navigation patterns (Navigation Compose)
- Creating adaptive layouts for phones, tablets, and foldables
- Using Material 3 theming with dynamic colors
- Building accessible Android interfaces
- Implementing Android-specific gestures and interactions
- Designing for different screen configurations

## Core Concepts

### 1. Material Design 3 Principles

**Personalization**: Dynamic color adapts UI to user's wallpaper
**Accessibility**: Tonal palettes ensure sufficient color contrast
**Large Screens**: Responsive layouts for tablets and foldables

**Material Components:**

- Cards, Buttons, FABs, Chips
- Navigation (rail, drawer, bottom nav)
- Text fields, Dialogs, Sheets
- Lists, Menus, Progress indicators

### 2. Jetpack Compose Layout System

**Column and Row:**

```kotlin
// Vertical arrangement with alignment
Column(
    modifier = Modifier.padding(16.dp),
    verticalArrangement = Arrangement.spacedBy(12.dp),
    horizontalAlignment = Alignment.Start
) {
    Text(
        text = "Title",
        style = MaterialTheme.typography.headlineSmall
    )
    Text(
        text = "Subtitle",
        style = MaterialTheme.typography.bodyMedium,
        color = MaterialTheme.colorScheme.onSurfaceVariant
    )
}

// Horizontal arrangement with weight
Row(
    modifier = Modifier.fillMaxWidth(),
    horizontalArrangement = Arrangement.SpaceBetween,
    verticalAlignment = Alignment.CenterVertically
) {
    Icon(Icons.Default.Star, contentDescription = null)
    Text("Featured")
    Spacer(modifier = Modifier.weight(1f))
    TextButton(onClick = {}) {
        Text("View All")
    }
}
```

**Lazy Lists and Grids:**

```kotlin
// Lazy column with sticky headers
LazyColumn {
    items.groupBy { it.category }.forEach { (category, categoryItems) ->
        stickyHeader {
            Text(
                text = category,
                modifier = Modifier
                    .fillMaxWidth()
                    .background(MaterialTheme.colorScheme.surface)
                    .padding(16.dp),
                style = MaterialTheme.typography.titleMedium
            )
        }
        items(categoryItems) { item ->
            ItemRow(item = item)
        }
    }
}

// Adaptive grid
LazyVerticalGrid(
    columns = GridCells.Adaptive(minSize = 150.dp),
    contentPadding = PaddingValues(16.dp),
    horizontalArrangement = Arrangement.spacedBy(12.dp),
    verticalArrangement = Arrangement.spacedBy(12.dp)
) {
    items(items) { item ->
        ItemCard(item = item)
    }
}
```

### 3. Navigation Patterns

**Bottom Navigation:**

```kotlin
@Composable
fun MainScreen() {
    val navController = rememberNavController()

    Scaffold(
        bottomBar = {
            NavigationBar {
                val navBackStackEntry by navController.currentBackStackEntryAsState()
                val currentDestination = navBackStackEntry?.destination

                NavigationDestination.entries.forEach { destination ->
                    NavigationBarItem(
                        icon = { Icon(destination.icon, contentDescription = null) },
                        label = { Text(destination.label) },
                        selected = currentDestination?.hierarchy?.any {
                            it.route == destination.route
                        } == true,
                        onClick = {
                            navController.navigate(destination.route) {