dat-conventions

Kotlin patterns, DatResult, session and capability conventions for DAT SDK Android development

npx skills add https://github.com/facebook/meta-wearables-dat-android --skill dat-conventions

DAT SDK Conventions (Android)

Quick Reference

Task	Command
Build app	`./gradlew assembleDebug`
Run tests	`./gradlew test`
Install app	`./gradlew installDebug`
Lint app	`./gradlew lint`

Architecture

The SDK is organized into four public modules:

mwdat-core: Registration, permissions, devices, and session creation
mwdat-camera: Stream capability, video frames, and photo capture
mwdat-display: Display capability, display UI components, icons, images, buttons, and video
mwdat-mockdevice: MockDeviceKit for testing without hardware

Initialization and session setup

Wearables.initialize(context)

val session = Wearables.createSession(AutoDeviceSelector()).getOrElse { error ->
    throw IllegalStateException(error.description)
}
session.start()

val camera = session.addCamera(StreamConfiguration()).getOrElse { error ->
    throw IllegalStateException(error.description)
}
camera.stream.start().getOrElse { error ->
    throw IllegalStateException(error.description)
}

Kotlin patterns

Use DatResult<T, E> for typed success and failure handling
Observe state with StateFlow and Flow
Create a Session first, then attach capabilities such as Stream or Display
Keep frame handling off the main thread when doing heavier processing

Error handling

Wearables.checkPermissionStatus(Permission.CAMERA)
    .onSuccess { status -> /* handle status */ }
    .onFailure { error, _ -> /* handle error */ }

Avoid getOrThrow() in user-facing samples. Surface typed errors from DatResult instead.

Naming conventions

Type	Purpose	Example
`Session`	Device connection lifecycle	`Wearables.createSession(...)`
`Stream`	Camera capability on a session	`session.addCamera(...)` → `camera.stream`
`Display`	Display capability on a session	`session.addDisplay(...)`
`*Selector`	Device targeting	`AutoDeviceSelector`
`*Error`	Typed failure surface	`SessionError`, `StreamError`

Key types

Wearables — SDK entry point
Session — lifecycle for an interaction with a linked device
Stream — camera capability attached to a session
Display — display capability attached to a session
StreamConfiguration — video quality and frame rate configuration
MockDeviceKit — simulated device environment for testing

Live docs search

If your editor supports remote MCP servers, connect https://mcp.developer.meta.com/wearables and use search_dat_docs for current DAT setup, session lifecycle, camera streaming, MockDeviceKit, permissions, and exact API symbols. This public docs server does not require authentication; do not configure tokens, OAuth, or custom authorization headers for it.

Use llms.txt when your tool only supports static reference context.

Testing with MockDeviceKit

val mockDeviceKit = MockDeviceKit.getInstance(context)
mockDeviceKit.enable()
val device = mockDeviceKit.pairGlasses(GlassesModel.RAYBAN_META).getOrThrow()

Use MockDeviceKit to drive registration, device availability, streaming media, and permission scenarios without physical hardware.

Common pitfalls

Do not call SDK APIs before Wearables.initialize(context)
Do not assume a session implies streaming or display access; capabilities are attached separately
Do not ignore DatResult failures from createSession, start, addCamera, addDisplay, or capturePhoto
Do not reuse terminally stopped sessions