Android Design Guidelines

1. Material You & Theming [CRITICAL]

1.1 Dynamic Color

Enable dynamic color derived from the user's wallpaper. Dynamic color is the default on Android 12+ and should be the primary theming strategy.

// Compose: Dynamic color theme
@Composable
fun AppTheme(
    darkTheme: Boolean = isSystemInDarkTheme(),
    dynamicColor: Boolean = true,
    content: @Composable () -> Unit
) {
    val colorScheme = when {
        dynamicColor && Build.VERSION.SDK_INT >= Build.VERSION_CODES.S -> {
            val context = LocalContext.current
            if (darkTheme) dynamicDarkColorScheme(context)
            else dynamicLightColorScheme(context)
        }
        darkTheme -> darkColorScheme()
        else -> lightColorScheme()
    }
    MaterialTheme(
        colorScheme = colorScheme,
        typography = AppTypography,
        content = content
    )
}

<!-- XML: Dynamic color in themes.xml -->
<style name="Theme.App" parent="Theme.Material3.DayNight.NoActionBar">
    <item name="dynamicColorThemeOverlay">@style/ThemeOverlay.Material3.DynamicColors.DayNight</item>
</style>

Rules:

• R1.1: Always provide a fallback static color scheme for devices below Android 12.
• R1.2: Never hardcode color hex values in components. Always reference color roles from the theme.
• R1.3: Test with at least 3 different wallpapers to verify dynamic color harmony.

1.2 Color Roles

Material 3 defines a structured set of color roles. Use them semantically, not aesthetically.

| Role | Usage | On-Role | |------|-------|---------| | primary | Key actions, active states, FAB | onPrimary | | primaryContainer | Less prominent primary elements | onPrimaryContainer | | secondary | Supporting UI, filter chips | onSecondary | | secondaryContainer | Navigation bar active indicator | onSecondaryContainer | | tertiary | Accent, contrast, complementary | onTertiary | | tertiaryContainer | Input fields, less prominent accents | onTertiaryContainer | | surface | Backgrounds, cards, sheets | onSurface | | surfaceVariant | Decorative elements, dividers | onSurfaceVariant | | error | Error states, destructive actions | onError | | errorContainer | Error backgrounds | onErrorContainer | | outline | Borders, dividers | — | | outlineVariant | Subtle borders | — | | inverseSurface | Snackbar background | inverseOnSurface |

// Correct: semantic color roles
Text(
    text = "Error message",
    color = MaterialTheme.colorScheme.error
)
Surface(color = MaterialTheme.colorScheme.errorContainer) {
    Text(text = "Error detail", color = MaterialTheme.colorScheme.onErrorContainer)
}

// WRONG: hardcoded colors
Text(text = "Error", color = Color(0xFFB00020)) // Anti-pattern

Rules:

• R1.4: Every foreground element must use the matching on color role for its background (e.g., onPrimary text on primary background).
• R1.5: Use surface and its variants for backgrounds. Never use primary or secondary as large background areas.
• R1.6: Use tertiary sparingly for accent and complementary contrast only.

1.3 Light and Dark Themes

Support both light and dark themes. Respect the system setting by default.

// Compose: Detect system theme
val darkTheme = isSystemInDarkTheme()

Rules:

• R1.7: Always support both light and dark themes. Never ship light-only.
• R1.8: Dark theme surfaces use elevation-based tonal mapping, not pure black (#000000). Use surface color roles which handle this automatically.
• R1.9: Provide a manual theme override in app settings (System / Light / Dark).

1.4 Custom Color Seeds

When branding requires custom colors, provide a seed color and generate tonal palettes using Material Theme Builder.

// Custom color scheme with brand seed
private val BrandLightColorScheme = lightColorScheme(
    primary = Color(0xFF1B6D2F),
    onPrimary = Color(0xFFFFFFFF),
    primaryContainer = Color(0xFFA4F6A8),
    onPrimaryContainer = Color(0xFF002107),
    // ... generate full palette from seed
)

Rules:

• R1.10: Generate tonal palettes from seed colors using Material Theme Builder. Never manually pick individual tones.
• R1.11: When using custom colors, still support dynamic color as the default and use custom colors as fallback.

---

2. Navigation [CRITICAL]

2.1 Navigation Bar (Bottom)

The primary navigation pattern for phones with 3-5 top-level destinations.

// Compose: Navigation Bar
NavigationBar {
    items.forEachIndexed { index, item ->
        NavigationBarItem(
            icon = {
                Icon(
                    imageVector = if (selectedItem == index) item.filledIcon else item.outlinedIcon,
                    contentDescription = item.label
                )
            },
            label = { Text(item.label) },
            selected = selectedItem == index,
            onClick = { selectedItem = index }
        )
    }
}

Rules:

• R2.1: Use Navigation Bar for 3-5 top-level destinations on compact screens. Never use for fewer than 3 or more than 5.
• R2.2: Always show labels on navigation bar items. Icon-only navigation bars are not permitted.
• R2.3: Use filled icons for the selected state and outlined icons for unselected states.
• R2.4: The active indicator uses secondaryContainer color. Do not override this.

2.2 Navigation Rail

For medium and expanded screens (tablets, foldables, desktop).

// Compose: Navigation Rail for larger screens
NavigationRail(
    header = {
        FloatingActionButton(
            onClick = { /* primary action */ },
            containerColor = MaterialTheme.colorScheme.tertiaryContainer
        ) {
            Icon(Icons.Default.Add, contentDescription = "Create")
        }
    }
) {
    items.forEachIndexed { index, item ->
        NavigationRailItem(
            icon = { Icon(item.icon, contentDescription = item.label) },
            label = { Text(item.label) },
            selected = selectedItem == index,
            onClick = { selectedItem = index }
        )
    }
}

Rules:

• R2.5: Use Navigation Rail on medium (600-839dp) and expanded (840dp+) window sizes. Pair it with Navigation Bar on compact.
• R2.6: Optionally include a FAB in the rail header for the primary action.
• R2.7: Labels are optional on the rail but recommended for clarity.

2.3 Navigation Drawer

For 5+ destinations or complex navigation hierarchies, typically on expanded screens.

// Compose: Permanent Navigation Drawer for large screens
PermanentNavigationDrawer(
    drawerContent = {
        PermanentDrawerSheet {
            Text("App Name", modifier = Modifier.padding(16.dp),
                 style = MaterialTheme.typography.titleMedium)
            HorizontalDivider()
            items.forEach { item ->
                NavigationDrawerItem(
                    label = { Text(item.label) },
                    selected = item == selectedItem,
                    onClick = { selectedItem = item },
                    icon = { Icon(item.icon, contentDescription = null) }
                )
            }
        }
    }
) {
    Scaffold { /* page content */ }
}

Rules:

• R2.8: Use modal drawer on compact screens, permanent drawer on expanded screens.
• R2.9: Group drawer items into sections with dividers and section headers.

2.4 Predictive Back Gesture

Android 13+ supports predictive back with an animation preview.

// Compose: Predictive back with BackHandler (androidx.activity.compose)
BackHandler(enabled = true) {
    // Called when back is confirmed; navigate back in your nav controller
    navController.popBackStack()
}

// Compose: Predictive back progress animation using predictiveBackHandler modifier
// (androidx.activity:activity-compose 1.8+)
Modifier.predictiveBackHandler(enabled = true) { progress ->
    // progress is a Flow<BackEventCompat> with x, y, swipeEdge, progress (0.0–1.0)
    progress.collect { backEvent ->
        animationState = backEvent.progress
    }
}

<!-- AndroidManifest.xml: opt in to predictive back -->
<application android:enableOnBackInvokedCallback="true">

Rules:

• R2.10: Opt in to predictive back in the manifest. In Compose apps, use BackHandler (from androidx.activity.compose) to intercept back events. In View-based apps, implement OnBackInvokedCallback (API 33+) or OnBackPressedCallback (AndroidX) instead of overriding onBackPressed().
• R2.11: The system back gesture navigates back in the navigation stack. The Up button (toolbar arrow) navigates up in the app hierarchy. These may differ.
• R2.12: Never intercept system back to show "are you sure?" dialogs unless there is unsaved user input.
• R2.13: Do not suppress the system-provided back preview animation. If you implement custom enter/exit transitions, interpolate them using BackEventCompat.progress (0.0–1.0) and respect BackEventCompat.swipeEdge (EDGE_LEFT/EDGE_RIGHT) so the exiting screen scales down and shifts toward the initiating edge, matching the system animation.
• R2.14: Prefer recognition over recall. Keep destinations labeled, selected state visible, and back-stack context preserved so users do not reconstruct where they are after every navigation step.

// Compose: drive a custom animation from predictive back progress
Modifier.predictiveBackHandler(enabled = true) { progress ->
    progress.collect { backEvent ->
        // backEvent.progress: 0.0 (gesture start) → 1.0 (committed)
        // backEvent.swipeEdge: BackEventCompat.EDGE_LEFT or EDGE_RIGHT
        exitScale = 1f - (backEvent.progress * 0.1f)
        exitOffsetX = if (backEvent.swipeEdge == BackEventCompat.EDGE_LEFT) -backEvent.progress * 32.dp.toPx() else backEvent.progress * 32.dp.toPx()
    }
}

2.5 Navigation Component Selection

| Screen Size | 3-5 Destinations | 5+ Destinations | |-------------|-------------------|-----------------| | Compact (< 600dp) | Navigation Bar | Modal Drawer + Navigation Bar | | Medium (600-839dp) | Navigation Rail | Modal Drawer + Navigation Rail | | Expanded (840dp+) | Navigation Rail | Permanent Drawer |

---

3. Layout & Responsive [HIGH]

3.1 Window Size Classes

Use window size classes for adaptive layouts, not raw pixel breakpoints.

// Compose: Window size classes
val windowSizeClass = calculateWindowSizeClass(this)
when (windowSizeClass.widthSizeClass) {
    WindowWidthSizeClass.Compact -> CompactLayout()
    WindowWidthSizeClass.Medium -> MediumLayout()
    WindowWidthSizeClass.Expanded -> ExpandedLayout()
}

| Class | Width | Typical Device | Columns | |-------|-------|----------------|---------| | Compact | < 600dp | Phone portrait | 4 | | Medium | 600-839dp | Tablet portrait, foldable | 8 | | Expanded | 840dp+ | Tablet landscape, desktop | 12 |

Rules:

• R3.1: Always use WindowSizeClass from material3-window-size-class for responsive layout decisions.
• R3.2: Never use fixed pixel breakpoints. Device categories are fluid.
• R3.3: Support all three width size classes. At minimum, compact and expanded.

3.2 Material Grid

Apply canonical Material grid margins and gutters.

| Size Class | Margins | Gutters | Columns | |------------|---------|---------|---------| | Compact | 16dp | 8dp | 4 | | Medium | 24dp | 16dp | 8 | | Expanded | 24dp | 24dp | 12 |

Rules:

• R3.4: Content should not span the full width on expanded screens. Use a max content width of ~840dp or list-detail layout.
• R3.5: Apply consistent horizontal margins matching the grid spec.

3.3 Edge-to-Edge Display

Android 15+ enforces edge-to-edge. All apps should draw behind system bars.

// Compose: Edge-to-edge setup
class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        enableEdgeToEdge()
        super.onCreate(savedInstanceState)
        setContent {
            Scaffold(
                modifier = Modifier.fillMaxSize(),
                // Scaffold handles insets for top/bottom bars automatically
            ) { innerPadding ->
                Content(modifier = Modifier.padding(innerPadding))
            }
        }
    }
}

Rules:

• R3.6: Call enableEdgeToEdge() before setContent. Draw behind both status bar and navigation bar.
• R3.7: Use WindowInsets to pad content away from system bars. Scaffold handles this for top bar and bottom bar content automatically.
• R3.8: Scrollable content should scroll behind transparent system bars with appropriate inset padding at the top and bottom of the list.

3.4 Foldable Device Support

// Compose: Detect fold posture
val foldingFeatures = WindowInfoTracker.getOrCreate(context)
    .windowLayoutInfo(context)
    .collectAsState(initial = WindowLayoutInfo(emptyList()))

Rules:

• R3.9: Detect hinge/fold position and avoid placing critical content across the fold.
• R3.10: Use ListDetailPaneScaffold or SupportingPaneScaffold from Material3 adaptive library for foldable-aware layouts.

---

4. Typography [HIGH]

4.1 Material Type Scale

| Role | Default Size | Default Weight | Usage | |------|-------------|----------------|-------| | displayLarge | 57sp | 400 | Hero text, onboarding | | displayMedium | 45sp | 400 | Large feature text | | displaySmall | 36sp | 400 | Prominent display | | headlineLarge | 32sp | 400 | Screen titles | | headlineMedium | 28sp | 400 | Section headers | | headlineSmall | 24sp | 400 | Card titles | | titleLarge | 22sp | 400 | Top app bar title | | titleMedium | 16sp | 500 | Tabs, navigation | | titleSmall | 14sp | 500 | Subtitles | | bodyLarge | 16sp | 400 | Primary body text | | bodyMedium | 14sp | 400 | Secondary body text | | bodySmall | 12sp | 400 | Captions | | labelLarge | 14sp | 500 | Buttons, prominent labels | | labelMedium | 12sp | 500 | Chips, smaller labels | | labelSmall | 11sp | 500 | Timestamps, annotations |

// Compose: Custom typography
val AppTypography = Typography(
    displayLarge = TextStyle(
        fontFamily = FontFamily(Font(R.font.brand_regular)),
        fontWeight = FontWeight.Normal,
        fontSize = 57.sp,
        lineHeight = 64.sp,
        letterSpacing = (-0.25).sp
    ),
    bodyLarge = TextStyle(
        fontFamily = FontFamily(Font(R.font.brand_regular)),
        fontWeight = FontWeight.Normal,
        fontSize = 16.sp,
        lineHeight = 24.sp,
        letterSpacing = 0.5.sp
    )
    // ... define all 15 roles
)

Rules:

• R4.1: Always use sp units for text sizes to support user font scaling preferences.
• R4.2: Never set text below 12sp for body content. Labels may go to 11sp minimum.
• R4.3: Reference typography roles from MaterialTheme.typography, not hardcoded sizes.
• R4.4: Support dynamic type scaling. Test at 200% font scale. Ensure no text is clipped or overlapping.
• R4.5: Line height should be approximately 1.2-1.5x the font size for readability.

---

5. Components [HIGH]

5.1 Floating Action Button (FAB)

The FAB represents the single most important action on a screen.

// Compose: FAB variants
// Standard FAB
FloatingActionButton(onClick = { /* action */ }) {
    Icon(Icons.Default.Add, contentDescription = "Create new item")
}

// Extended FAB (with label - preferred for clarity)
ExtendedFloatingActionButton(
    onClick = { /* action */ },
    icon = { Icon(Icons.Default.Edit, contentDescription = null) },
    text = { Text("Compose") }
)

// Large FAB
LargeFloatingActionButton(onClick = { /* action */ }) {
    Icon(Icons.Default.Add, contentDescription = "Create", modifier = Modifier.size(36.dp))
}

Rules:

• R5.1: Use at most one FAB per screen. It represents the primary action.
• R5.2: Place the FAB at the bottom-end of the screen. On screens with a Navigation Bar, the FAB floats above it.
• R5.3: The FAB should use primaryContainer color by default. Use tertiaryContainer for secondary screens.
• R5.4: Prefer ExtendedFloatingActionButton with a label for clarity. Collapse to icon-only on scroll if needed.

5.2 Top App Bar

// Compose: Top app bar variants
// Small (default)
TopAppBar(
    title = { Text("Page Title") },
    navigationIcon = {
        IconButton(onClick = { /* navigate up */ }) {
            Icon(Icons.AutoMirrored.Filled.ArrowBack, contentDescription = "Back")
        }
    },
    actions = {
        IconButton(onClick = { /* search */ }) {
            Icon(Icons.Default.Search, contentDescription = "Search")
        }
    }
)

// Medium — expands title area
MediumTopAppBar(
    title = { Text("Section Title") },
    scrollBehavior = TopAppBarDefaults.enterAlwaysScrollBehavior()
)

// Large — for prominent titles
LargeTopAppBar(
    title = { Text("Screen Title") },
    scrollBehavior = TopAppBarDefaults.exitUntilCollapsedScrollBehavior()
)

Rules:

• R5.5: Use TopAppBar (small) for most screens. Use MediumTopAppBar or LargeTopAppBar for prominent section or screen titles.
• R5.6: Connect scroll behavior to the app bar so it collapses/expands with content scrolling.
• R5.7: Limit action icons to 2-3. Overflow additional actions into a more menu.

5.3 Bottom Sheets

// Compose: Modal bottom sheet
ModalBottomSheet(
    onDismissRequest = { showSheet = false },
    sheetState = rememberModalBottomSheetState()
) {
    Column(modifier = Modifier.padding(16.dp)) {
        Text("Sheet Title", style = MaterialTheme.typography.titleLarge)
        Spacer(modifier = Modifier.height(16.dp))
        // Sheet content
    }
}

Rules:

• R5.8: Use modal bottom sheets for non-critical supplementary content. Use standard bottom sheets for persistent content.
• R5.9: Bottom sheets must have a visible drag handle for discoverability.
• R5.10: Sheet content must be scrollable if it can exceed the visible area.

5.4 Dialogs

// Compose: Alert dialog
AlertDialog(
    onDismissRequest = { showDialog = false },
    title = { Text("Discard draft?") },
    text = { Text("Your unsaved changes will be lost.") },
    confirmButton = {
        TextButton(onClick = { /* confirm */ }) { Text("Discard") }
    },
    dismissButton = {
        TextButton(onClick = { showDialog = false }) { Text("Cancel") }
    }
)

Rules:

• R5.11: Dialogs interrupt the user. Use them only for critical decisions requiring immediate attention.
• R5.12: Confirm button uses a text button, not a filled button. The dismiss button is always on the left.
• R5.13: Dialog titles should be concise questions or statements. Body text provides context.

5.5 Snackbar

// Compose: Snackbar with action
val snackbarHostState = remember { SnackbarHostState() }
Scaffold(snackbarHost = { SnackbarHost(snackbarHostState) }) {
    // trigger snackbar
    LaunchedEffect(key) {
        val result = snackbarHostState.showSnackbar(
            message = "Item archived",
            actionLabel = "Undo",
            duration = SnackbarDuration.Short
        )
        if (result == SnackbarResult.ActionPerformed) { /* undo */ }
    }
}

Rules:

• R5.14: Use snackbars for brief, non-critical feedback. They auto-dismiss and should not contain critical information.
• R5.15: Snackbars appear at the bottom of the screen, above the Navigation Bar and below the FAB.
• R5.16: Include an action (e.g., "Undo") when the operation is reversible. Limit to one action.

5.6 Chips

// Filter Chip
FilterChip(
    selected = isSelected,
    onClick = { isSelected = !isSelected },
    label = { Text("Filter") },
    leadingIcon = if (isSelected) {
        { Icon(Icons.Default.Check, contentDescription = null, modifier = Modifier.size(18.dp)) }
    } else null
)

// Assist Chip
AssistChip(
    onClick = { /* action */ },
    label = { Text("Add to calendar") },
    leadingIcon = { Icon(Icons.Default.CalendarToday, contentDescription = null) }
)

Rules:

• R5.17: Use FilterChip for toggling filters, AssistChip for smart suggestions, InputChip for user-entered content (tags), SuggestionChip for dynamically generated suggestions.
• R5.18: Chips should be arranged in a horizontally scrollable row or a flow layout, not stacked vertically.
• R5.19: Expose waiting states immediately. If an action cannot finish right away, acknowledge it with inline state change, progress, or another visible response rather than leaving the UI static.

5.7 Component Selection Guide

| Need | Component | |------|-----------| | Primary screen action | FAB | | Brief feedback | Snackbar | | Critical decision | Dialog | | Supplementary content | Bottom Sheet | | Toggle filter | Filter Chip | | User-entered tag | Input Chip | | Smart suggestion | Assist Chip | | Content group | Card | | Vertical list of items | LazyColumn with ListItem | | Segmented option (2-5) | SegmentedButton | | Binary toggle | Switch | | Selection from list | Radio buttons or exposed dropdown menu |

---

6. Accessibility [CRITICAL]

6.1 TalkBack and Content Descriptions

// Compose: Accessible components
Icon(
    Icons.Default.Favorite,
    contentDescription = "Add to favorites" // Descriptive, not "heart icon"
)

// Decorative elements
Icon(
    Icons.Default.Star,
    contentDescription = null // null for purely decorative
)

// Merge semantics for compound elements
Row(modifier = Modifier.semantics(mergeDescendants = true) {}) {
    Icon(Icons.Default.Event, contentDescription = null)
    Text("March 15, 2026")
}

// Custom actions
Box(modifier = Modifier.semantics {
    customActions = listOf(
        CustomAccessibilityAction("Archive") { /* archive */ true },
        CustomAccessibilityAction("Delete") { /* delete */ true }
    )
})

Rules:

• R6.1: Every interactive element must have a contentDescription (or null if purely decorative).
• R6.2: Content descriptions must describe the action or meaning, not the visual appearance. Say "Add to favorites" not "Heart icon."
• R6.3: Use mergeDescendants = true to group related elements into a single TalkBack focus unit (e.g., a list item with icon + text + subtitle).
• R6.4: Provide customActions for swipe-to-dismiss or long-press actions so TalkBack users can access them.

6.2 Touch Targets

// Compose: Ensure minimum touch target
IconButton(onClick = { /* action */ }) {
    // IconButton already provides 48dp minimum touch target
    Icon(Icons.Default.Close, contentDescription = "Close")
}

// Manual minimum touch target
Box(
    modifier = Modifier
        .sizeIn(minWidth = 48.dp, minHeight = 48.dp)
        .clickable { /* action */ },
    contentAlignment = Alignment.Center
) {
    Icon(Icons.Default.Info, contentDescription = "Info", modifier = Modifier.size(24.dp))
}

Rules:

• R6.5: All interactive elements must have a minimum touch target of 48x48dp. Material 3 components handle this by default.
• R6.6: Do not reduce touch targets to save space. Use padding to increase the touchable area if the visual element is smaller.

6.3 Color Contrast and Visual

Rules:

• R6.7: Text contrast ratio must be at least 4.5:1 for normal text and 3:1 for large text (18sp+ or 14sp+ bold) against its background.
• R6.8: Never use color as the only means of conveying information. Pair with icons, text, or patterns.
• R6.9: Support bold text and high contrast accessibility settings. Use Configuration.fontWeightAdjustment (API 31+) to detect the user's bold text preference and scale custom font weights accordingly. Use AccessibilityManager.isHighTextContrastEnabled() to de

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