/hz-android-2d-porting

name: hz-android-2d-porting
license: Apache-2.0
description: Guides porting existing Android 2D apps to Meta Quest and Horizon OS — input adaptation, panel layout, and design requirements. Use when adapting a mobile Android app for Quest.
allowed-tools: Bash(metavr:*) Bash(hzdb:*)

Android 2D App Porting to Horizon OS

When to Use

Use this skill when:

• Porting an existing Android 2D app to run on Meta Quest headsets
• Adapting a mobile Android app for Horizon OS panels
• Troubleshooting input, layout, or compatibility issues with a 2D app on Quest
• Preparing an Android app for Horizon Store submission
• Evaluating whether an existing Android app is compatible with Horizon OS

Overview

Horizon OS is built on Android (AOSP) and can run standard Android applications inside **panels** -- floating 2D windows positioned in 3D space. Most well-built Android apps work on Quest with minimal changes, but several areas require attention:

1. **Input**: There is no touchscreen. Users interact via controller pointer (ray-casting), hand tracking, or connected peripherals. 2. **Layout**: Apps run in resizable panels, not full-screen on a fixed display. 3. **Design**: Apps must meet Horizon OS design requirements for Horizon Store approval. 4. **Performance**: Quest uses a mobile GPU (Adreno) with thermal constraints.

The goal of porting is to make the app feel native to the Quest experience while preserving existing functionality.

Porting Workflow

Step 1: Initial Testing

Invoke metavr (the Quest device CLI) via `metavr <args>`. The command is published as the npm package `metavr`, so if `metavr` is not on PATH you can run the same CLI via `npx -y metavr <args>` — no global install needed; npx fetches the latest published version on demand.

The examples in this doc call `metavr` directly; the `npx -y metavr <args>` form above is the equivalent when `metavr` is not on PATH (the published npm package is still `metavr`).

Install the existing APK on a connected Quest device and test basic functionality:

metavr app install path/to/your-app.apk
metavr app launch com.example.yourapp

Note any immediate issues: crashes, black screens, input problems, or layout breakage.

Step 2: Input Adaptation

The most common porting issue is input. Touch events are translated from the controller pointer, but:

• **Hover states** are now visible (users point before clicking)
• **Scrolling** uses the thumbstick, not swipe gestures
• **Multi-touch** gestures (pinch-to-zoom) do not translate directly
• **Tap targets** must be large enough for pointer accuracy (48dp minimum)

See [Input Adaptation Reference](references/input-adaptation.md) for detailed guidance.

Step 3: Layout Adjustment

Panels are resizable and can have various aspect ratios. Your app must handle:

• Dynamic width and height changes
• Landscape and portrait orientations
• Different effective DPI values

Use responsive layout strategies such as `ConstraintLayout` or Jetpack Compose. See [Panel Layout Reference](references/panel-layout.md).

Step 4: Gradle and Manifest Updates

Update your build configuration to target Horizon OS:

// build.gradle.kts
android {
    defaultConfig {
        minSdk = 29       // Android 10 minimum
        targetSdk = 34    // API 34 or higher required for all new 2D panel apps
    }
}

Add required manifest entries for device targeting. See [Gradle Setup Reference](references/gradle-setup.md).

Step 5: Input Testing

Test with all supported input methods:

• **Controller**: point-and-click, thumbstick scroll, trigger tap
• **Hand tracking**: pinch-to-select, hand scroll
• **Keyboard/mouse**: Bluetooth peripherals, system keyboard for text fields

Use the XR Simulator for rapid iteration, then validate on-device.

Step 6: Store Submission

Before submitting to the Horizon Store:

• Verify all [Compatibility Requirements](references/compatibility-requirements.md)
• Test on at least Quest 3 and Quest 2 (if targeting both)
• Confirm the app works in both passthrough and immersive home environments
• Review Meta's content policies and technical requirements

Quick Compatibility Check

Works on Horizon OS

| Feature | Status | Notes | |---|---|---| | Standard Android Views | Supported | TextView, RecyclerView, etc. | | Jetpack Compose | Supported | Full Compose UI toolkit | | WebView | Supported | Chromium-based | | Media playback (ExoPlayer) | Supported | Video and audio | | Networking (HTTP, WebSocket) | Supported | Wi-Fi connectivity | | Room / SQLite | Supported | Local database | | WorkManager | Supported | Background tasks | | Notifications | Supported | Horizon OS notification panel | | Bluetooth (peripherals) | Supported | Keyboard, mouse, gamepad | | Android Accessibility APIs | Supported | TalkBack equivalent available |

Restricted or Unavailable

| Feature | Status | Notes | |---|---|---| | Camera (front-facing) | Not available | No standard camera in 2D mode | | Telephony / SMS | Not available | No cellular radio | | NFC | Not available | No NFC hardware | | GPS / Fine location | Limited | Wi-Fi-based location only | | Fingerprint / BiometricPrompt | Not available | Use Meta account auth instead | | Split-screen (multi-window) | Limited | Use Spatial SDK panels instead | | Google Play Services | Not available | Use Meta equivalents or alternatives | | ARCore | Not available | Use Meta Spatial SDK for spatial features | | Multi-touch gestures | Limited | Single pointer from controller |

Common Issues and Fixes

| Issue | Cause | Fix | |---|---|---| | App crashes on launch | Missing Google Play Services dependency | Remove or make GMS optional | | Buttons too small to tap | Touch targets under 48dp | Increase minimum tap target size | | No scroll in lists | Swipe-based scroll not triggered | Ensure `RecyclerView`/`LazyColumn` handles generic scroll events | | Keyboard doesn't appear | Custom input field not using `InputConnection