Android UX

Android UX

This reference covers the non-obvious platform facts and reviewing an existing screen for M3 compliance, not the basics of building M3-correct UI.

Non-obvious platform facts

Foldable postures

Foldables introduce postures beyond window size classes. Detect them with WindowInfoTracker + FoldingFeature (Jetpack WindowManager), and never place interactive content or critical information across the hinge.

Posture	Detection	Layout behavior
Flat (unfolded)	no folding feature	Treat as Medium/Expanded by width
Half-opened, horizontal fold (tabletop)	HALF_OPENED + Orientation.HORIZONTAL	Content above the hinge, controls below it — read the hinge bounds, never assume a 50/50 split
Half-opened, vertical fold (book)	HALF_OPENED + Orientation.VERTICAL	List left, detail right
Folded (cover screen)	—	Treat as Compact

On current Compose, the adaptive APIs replace the manual tracker: mediaQuery { windowPosture == UiMediaScope.Posture.Tabletop } — see Google's adaptive skill (android skills add adaptive). The WindowInfoTracker form below works on older versions.

@Composable
fun FoldAwareLayout() {
    val context = LocalContext.current
    val layoutInfo by WindowInfoTracker.getOrCreate(context)
        .windowLayoutInfo(context)  // accepts @UiContext — Activity, InputMethodService, or createWindowContext()
        .collectAsStateWithLifecycle(initialValue = WindowLayoutInfo(emptyList()))

    val fold = layoutInfo.displayFeatures.filterIsInstance<FoldingFeature>().firstOrNull()
    when {
        fold?.state == FoldingFeature.State.HALF_OPENED ->
            if (fold.orientation == FoldingFeature.Orientation.HORIZONTAL) TabletopLayout() else BookLayout()
        else -> StandardAdaptiveLayout()  // by window size class
    }
}

M3 contrast levels (user-controlled contrast)

Compose's dynamicLightColorScheme / dynamicDarkColorScheme read the system contrast setting automatically (SDK 34+) and expose no contrast parameter. To offer in-app contrast control (Standard 0.0 / Medium 0.5 / High 1.0 tonal distance), build the scheme from Hct + SchemeContent:

// com.google.android.material:material (MDC-Android), package com.google.android.material.color.utilities
// Marked @RestrictTo(LIBRARY_GROUP) — internal API, may change between versions; re-check on version bumps.
val hct = Hct.fromInt(0xFF6750A4.toInt())
val scheme = SchemeContent(hct, /* isDark = */ false, /* contrastLevel = */ 1.0)
val colorScheme = lightColorScheme(
    primary = Color(scheme.primary),
    onPrimary = Color(scheme.onPrimary),
    // ... map remaining roles
)

For multiplatform or a stable public API, com.materialkolor:material-color-utilities is a KMP alternative.

Motion: duration tokens + reduced motion

Use M3's duration ladder rather than arbitrary millis, and pick easing by what the element does — decelerate to enter, accelerate to exit, emphasized to move on screen (values in compose/references/animation.md). Reach for MotionScheme (Compose M3 1.4+) where available; otherwise hold durations at one source of truth in the theme.

Token group	Range	Typical use
short1…short4	50–200ms	Micro-interactions, state changes (ripple, selection, switch)
medium1…medium4	250–400ms	Standard transitions (screen enter/exit, expansion, reveal)
long1…long4	450–600ms	Container transforms, fade-through between large surfaces
extraLong1…extraLong4	700–1000ms	Shared-element / hero transitions on tablets/foldables

Animations must be interruptible and never block input. Reduced motion: Compose already applies the system animator duration scale to its animations (through MotionDurationScale), so with animations off they finish instantly — no code needed for that. Add the local below only to swap the motion design, e.g. drop a slide and keep nothing; Compose has no built-in LocalReducedMotion:

val LocalReducedMotion = staticCompositionLocalOf { false }

@Composable
fun AppTheme(content: @Composable () -> Unit) {
    val context = LocalContext.current
    val reduceMotion = remember {
        Settings.Global.getFloat(context.contentResolver, Settings.Global.ANIMATOR_DURATION_SCALE, 1f) == 0f
    }
    CompositionLocalProvider(LocalReducedMotion provides reduceMotion) { MaterialTheme { content() } }
}

// at the call site
AnimatedVisibility(
    visible = isVisible,
    enter = if (LocalReducedMotion.current) EnterTransition.None else fadeIn() + slideInVertically(),
) { Content() }

(staticCompositionLocalOf + keyless remember read the setting once per Activity; for live updates switch to compositionLocalOf + a ContentObserver on ANIMATOR_DURATION_SCALE.)

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M3 Compliance Audit

Use this when reviewing a screen or feature for Material Design 3 compliance — the part that's easy to skip from memory. Score each category Pass / Partial / Fail, then fix any Partial/Fail before shipping.

1. Color tokens

• All colors reference MaterialTheme.colorScheme roles — no hardcoded hex/ARGB.
• Correct role usage: primary for key actions, secondary/tertiary for less prominent / accents, error for errors; on* paired correctly; layered surfaces via surfaceContainerLow/High, not arbitrary grays.
• Outlines: outline for interactive boundaries needing 3:1 (field borders, focus rings), outlineVariant for decorative dividers.
• Dynamic color on Android 12+ with a static fallback.

2. Typography

• All text from MaterialTheme.typography — no inline fontSize/fontWeight.
• Correct scale: display* hero, headline* section headers, title* card/dialog titles, body* content, label* buttons/captions.

3. Shape

• Corner radii from MaterialTheme.shapes, not hardcoded RoundedCornerShape.
• Scale: extraSmall (4dp) chips, small (8dp) cards, medium (12dp) dialogs, large (16dp) sheets, extraLarge (28dp) FABs. Consistent shape language.

4. Elevation & surface

• Elevation via tonal color (surface containers), not drop shadows; shadow elevation reserved for dialogs/menus/FABs.
• ElevatedCard/ElevatedButton over manual shadowElevation.
• Container hierarchy monotonic by tone (surfaceContainerLowest < … < Highest) — if two adjacent layers render the same color in either theme, the elevation cue is broken.

5. Components

• M3 components (androidx.compose.material3.*), no M2 (androidx.compose.material.*) and no M2/M3 mixing on a screen.
• Used as intended: FloatingActionButton for the primary action, Card for grouped content, TopAppBar for screen-level actions.

Quick grep checks

Run from the project root — each hit is a category-1/3/5 violation to triage before human review:

rg --type kt 'Color\(0x[0-9a-fA-F]{6,8}\)' --files-with-matches | head            # 1: hardcoded colors
rg --type kt 'RoundedCornerShape\(\s*\d+(?:\.\d+)?\s*\.dp\s*\)' --files-with-matches | head  # 3: hardcoded radii
rg --type kt 'import androidx\.compose\.material\.' --files-with-matches | head    # 5: Material 2 imports

6. Layout & spacing

• 8dp grid for padding/margins; responsive compact/medium/expanded breakpoints; screen maps to a canonical layout (Feed, List-Detail, Supporting Pane).
• Content width constrained on wide screens — cap body content at ~840–1040dp on Large and center it; full width is for navigation chrome, not paragraphs.
• Foldable postures handled (no content across the hinge; tabletop/book layouts where relevant).
• Dialogs centered (not full-screen) on Medium+; bottom sheets convert to side sheets on Expanded+.

7. Navigation

• Navigation component matches width (Bottom Bar / Rail / Drawer); items have both icon and label; current destination indicated via selected + active indicator.

8. Motion

• Transitions use M3 easing + duration tokens; shared elements use Emphasized at 300–500ms; enter/exit follow M3 (fade-through, container transform); interruptible and respect reduced motion.

9. Accessibility

• Meaningful images/icons have contentDescription; contrast meets WCAG AA (4.5:1 body, 3:1 large text + UI components); touch targets ≥48dp.
• Composite items merged with semantics(mergeDescendants = true) so TalkBack announces them as one unit (icon contentDescription = null when merged).
• Section titles marked semantics { heading() } so screen-reader users can jump between sections.
• Traversal order logical (semantics { traversalIndex } where needed). User-controlled contrast (Standard/Medium/High) considered if supported.

10. Theming consistency

• Single MaterialTheme (no nested/conflicting themes); light + dark both tested; custom theme extensions via CompositionLocal, not globals; brand colors via a custom ColorScheme, not per-component overrides.

Audit summary template

Screen: [name]   Date: [date]

| # | Category            | Score   | Notes                  |
|---|---------------------|---------|------------------------|
| 1 | Color tokens        | Pass    |                        |
| 2 | Typography          | Partial | bodySmall hardcoded    |
| 5 | Components          | Fail    | M2 Scaffold still used |
| 6 | Layout & spacing    | Partial | No tablet breakpoint   |
| 9 | Accessibility       | Partial | Missing headings       |
…

Action items:
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