41 lines
3.1 KiB
Markdown
41 lines
3.1 KiB
Markdown
# Android platform
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For native Android apps: Jetpack Compose, Android Views, React Native, Expo, Flutter shipping to Android hardware.
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On native, register narrows. Material Design 3 governs structure, navigation, and interaction whatever the register; brand expresses through Material's theming (color roles, type scale, shape, motion). A Material-everywhere cross-platform app that also ships to iPhone still owes iOS its OS guarantees on that hardware: safe-area insets, Reduce Motion, edge-swipe back.
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## The Android slop test
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Would a fluent Android user trust this app, or trip on off-spec components? The most common tell is an iOS app wearing Android's skin: a bottom-only navigation copied from iPhone, a back arrow that ignores the system Back gesture, Cupertino-shaped switches and dialogs. Material 3 is the rulebook; follow its components and theme the brand through it.
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## Layout & structure
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- **Material navigation, matched to size.** Navigation bar (bottom, 3–5 destinations) on compact width; navigation rail or drawer on expanded width. Never ship a phone bottom-bar untouched on a tablet.
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- **System Back always works.** Honor the predictive Back gesture and Back button; never trap the user or hijack the gesture.
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- **Edge-to-edge with window insets.** Apply the status bar, navigation bar, display cutout, and IME insets so content never hides behind system bars or the keyboard.
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- **Top app bar for screen context**; pair with a FAB when the screen has a single primary action.
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## Touch targets
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- **48×48 dp minimum** for every touch target, with at least 8 dp between them.
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## Typography
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- **Material type scale.** Display, Headline, Title, Body, Label roles (large/medium/small each). Map text to roles; never hand-pick sizes per screen.
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- **Roboto is the system face**; theme a brand face in through the type scale, keeping body, labels, and controls legible and consistent.
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- **sp units, never fixed px**, so type follows the system font-size setting.
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## Color & theming
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- **Material color roles** (primary, on-primary, surface, surface-variant, secondary-container, outline, error). Role tokens resolve light/dark and contrast variants automatically; raw hex breaks there.
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- **Dynamic Color (Material You)** where it fits: derive the scheme from the user's wallpaper on Android 12+, with a static fallback.
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- **Dark theme is a first-class scheme.** Design and test it; never a quick invert.
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- **Tonal elevation.** Convey elevation through the standard surface tonal levels (plus shadow where appropriate); no arbitrary drop shadows.
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## Components & motion
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- **Material components.** Buttons (filled / tonal / outlined / text), FAB, switches, chips, snackbars, bottom sheets, Material dialogs, navigation bar/rail/drawer. Never port iOS controls or invent equivalents.
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- **One FAB, one primary action.** Never stack FABs or spend one on a secondary task.
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- **Snackbars for transient feedback** (actionable when useful, never a toast for that); dialogs only for decisions that must interrupt.
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- **Material motion patterns.** Container transform, shared-axis, fade-through, with standard easing and durations; honor the system Remove animations setting with a crossfade or instant cut.
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