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

Install hzdb (the Quest device CLI) if you haven't already:

npm install -g @meta-quest/hzdb

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

hzdb app install path/to/your-app.apk
hzdb 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 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.

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    // 32-34 for immersive apps, 32-36 for 2D apps
    }
}

Add required manifest entries for device targeting. See Gradle Setup Reference.

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
• 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

Restricted or Unavailable

Common Issues and Fixes

Key Concepts

Compatibility Mode vs Native Targeting

Apps not specifically targeting Horizon OS run in compatibility mode:

• Fixed panel size (simulating a phone screen)
• Limited resizing
• Basic input translation

Apps that target Horizon OS with proper manifest entries run in native mode:

• Resizable panels
• Full input API support
• Access to Spatial SDK features (optional)
• Better integration with Horizon OS shell

Testing Tools

• hzdb: Command-line tool for installing, launching, and debugging apps on Quest
• XR Simulator: Desktop tool for testing Quest apps without a headset
• Meta Quest Developer Hub (MQDH): GUI tool for device management and debugging
• Android Studio: Full IDE with Quest device support via ADB

Performance Considerations

Quest devices have mobile-class hardware with strict thermal limits:

• GPU: Qualcomm Adreno (varies by Quest model)
• RAM: 6-12 GB shared between system and apps
• Thermal: Sustained workloads may trigger thermal throttling
• Avoid heavy overdraw and complex shader effects in 2D UI
• Minimize background work to reduce power consumption
• Test with representative data loads (large lists, images, etc.)

References

• Compatibility Requirements -- store requirements and API compatibility
• Input Adaptation -- adapting touch to controller and hand input
• Panel Layout -- responsive layout for Horizon OS panels
• Gradle Setup -- build configuration and manifest entries