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Views platform

Guidelines for implementing and consuming Cabin with Android Views / XML — essential for SystemUI, status bar, CarLauncher, other AOSP build-tree apps, and legacy surfaces that cannot yet adopt Compose.

Role of Views in Cabin​

Views are not a compatibility afterthought. They are the primary stack for platform chrome. Many AAOS images deliver SystemUI and vendor apps as View hierarchies built with Soong. Cabin’s Views stack must be as intentional as Compose: tokenized, compliance-aware, and parity-tested.

Compose remains first-class for apps and for platform apps that already use it — but Compose is not a gate for SystemUI adoption (build-tree).

Planned artifacts​

PathIdentifierStatus
Maven (Gradle apps)dev.decoupled.cabin:cabin-views:<version>Alpha (Theme Kit + System/Status bars)
Soong (build-tree)CabinViewsAlpha sketch cabin-views/Android.bp

Depends on cabin-tokens / CabinTokens and cabin-compliance / CabinCompliance for restriction-aware bars. Does not depend on cabin-compose / CabinCompose. No AppCompat / Material (platform DayNight parent).

Theme and attributes​

Theme Kit (Alpha) lives in cabin-views — see theme-kit.

  • Styles: Theme.Cabin / Theme.Cabin.DayNight, ThemeOverlay.Cabin
  • Attrs (cabin_color*) defined in cabin-tokens; Theme Kit binds them to semantic + scheme color resources (day/night via values-night)
  • Resolve in code with CabinThemeResolver — no hardcoded hex in widgets
  • OEM brand via theme overlay / RRO without forking (ADR 0003, build-tree)
<style name="Theme.Cabin" parent="@android:style/Theme.DeviceDefault.DayNight">
    <!-- Token-backed cabin_* attributes (see cabin-views res); NoActionBar via window flags -->
</style>

System/Status bar widgets: CabinSystemBarView, CabinStatusBarView (Alpha).

Implementation guidelines​

TopicCabin rule
InflationSafe in system UI contexts; avoid Compose-only assumptions
ConfigurationHandle day/night and locale without losing vehicle state
State bindingExplicit bind() / adapters; no hidden global singletons
Focus / rotaryfocusable, orderly nextFocus*, visible focus from tokens
AccessibilitycontentDescription, important-for-accessibility set correctly
PerformanceAvoid overdraw in persistent chrome; flatten where practical
TestingRobolectric/instrumentation + screenshot; shared fixtures with Compose; on-image tests for SystemUI

Compliance wiring​

val host = CabinComplianceHost(initialState = VehicleUiState.parked())
systemBar.setCompliance(host)
statusBar.setCompliance(host)
host.updateState(adapterState) // map CarUxRestrictions → VehicleUiState

Gated click listeners disable or substitute interactions consistently with Compose (driving). Null compliance host is fail-closed (Block) so chrome cannot activate ungated.

Parity contracts with Compose​

Same table as compose.md: shared state/actions, token sizes, gating, unavailable UI, day/night roles. Views may use XML layouts for driving substitutes (layout / layout-driving patterns or programmatic swap) but outcomes must match Compose substitutes.

System UI and build-tree adoption​

Primary Views consumers:

TargetConsumption
SystemUI / status + system barsSoong: CabinTokens + CabinCompliance + CabinViews
CarLauncherSoong Views path; Compose only if that subtree already uses it
Platform media (Views)Soong CabinViews
Gradle-built legacy appsMaven cabin-views

Rules:

  • Keep dependencies minimal — tokens + compliance + views only (packaging, build-tree).
  • Never pull CabinCompose, catalog, or samples into SystemUI.
  • Prefer source-in-tree over AAR prebuilts for privileged chrome.
  • Soong engineering notes: soong.

Interop​

  • Host Compose islands via ComposeView when a subtree is Compose-first (apps / Compose-capable platform modules only).
  • Do not create a cyclic Gradle or Soong dependency between stacks.

Do not​

  • Reintroduce handheld-sized touch targets via AppCompat defaults without Cabin style overlays.
  • Encode OEM brand in widget source.
  • Skip unavailable/stale signal UI because “Views make it hard.”
  • Document or implement SystemUI adoption as a Gradle implementation of Cabin AARs.