Jetpack Compose is the modern Android UI framework — declarative Kotlin UI that has replaced the old XML layouts. Material 3 is Google's current design system, wired up here with dynamic (wallpaper-based) color on Android 12+.

Layout

flake.nix                     Nix entrypoint: dev shells, SDK, package, emulator
package.nix                   Reproducible APK build (nixpkgs-style derivation)
deps.json                     Lockfile of Gradle/Maven deps (generated — see below)
settings.gradle.kts           Gradle project + repositories
build.gradle.kts              Root build script (declares plugin versions)
gradle/libs.versions.toml     Version catalog: all dependency/plugin versions
app/
  build.gradle.kts            The :app module (Android + Compose config)
  src/main/
    AndroidManifest.xml       App/activity declaration
    kotlin/ca/ksamad/musicremote/
      MainActivity.kt         Entry activity; sets the Compose content
      Theme.kt                Material 3 theme (dynamic color)
    res/values/               strings.xml, themes.xml
  src/test/kotlin/...         A plain JVM unit test

Everyday Development (Recommended)

Use the dev shell — it puts a JDK, Gradle, and the Android SDK on your PATH with the right environment variables set:

nix develop
gradle assembleDebug        # build the debug APK -> app/build/outputs/apk/debug/
gradle testDebugUnitTest    # run unit tests
gradle tasks                # see everything available

The debug APK is unsigned but installable on a device/emulator:

adb install app/build/outputs/apk/debug/app-debug.apk

Android Studio

For the GUI editor, Compose previews, and device manager:

nix develop .#studio
android-studio

Open this folder as an existing project. (Android Studio manages its own SDK; the command-line flow above is fully independent of it.)

Emulator

nix run .#emulate

Reproducible Build with Nix

nix build          # -> ./result/music-remote.apk

Unlike gradle assembleDebug, this build runs fully offline: every Gradle/Maven dependency is pinned by hash in deps.json, and Nix supplies the Android SDK. It also runs the unit tests (testDebugUnitTest) as its check phase, so a green nix build means both "it assembles" and "tests pass". This is what you'd use in CI for a reproducible artifact.

Note: package.nix and app/build.gradle.kts contain a few small workarounds, active only during dependency capture (gated on the IN_GRADLE_UPDATE_DEPS env var), that stop Nix's "resolve every configuration" sweep from tripping over internal AGP/Kotlin configurations. They don't affect the dev shell or the actual build. See the comments in app/build.gradle.kts for the details.

Regenerating `deps.json`

Any time you change a dependency or plugin version (i.e. edit gradle/libs.versions.toml or a build.gradle.kts), regenerate the lockfile:

nix build .#default.mitmCache.updateScript
./result                    # runs the build under a proxy, rewrites ./deps.json

Then commit the updated deps.json. (It works by recording Gradle's dependency downloads through a man-in-the-middle proxy and storing their hashes — see package.nix.)

Docs

docs/device-testing.md — build & install onto a real Android device/DAP over USB (and the NixOS adb notes).
docs/TODO.md — near-term roadmap / known bugs.

Version notes

Pinned in gradle/libs.versions.toml: AGP 8.7.3, Kotlin 2.0.21, Compose BOM 2024.10.01, compiled against compileSdk 35, minSdk 24. Nix supplies Gradle 8.14. If you bump these, keep AGP/Kotlin/Gradle mutually compatible and regenerate deps.json.

README.md

Music Remote