Android app (experimental)

A FOSS Android frontend to the same HARP core, living in the repo's android/ directory. The app embeds src/harp directly via Chaquopy (MIT), so app and CLI can never drift apart.

Current features:

• Spike screen — proves the on-device astro stack (numpy, astropy, astroplan, harp) by computing tonight's darkness window on the phone.
• Horizon wizard — the reason the app exists: live true-north azimuth/altitude from the fused rotation-vector sensor, magnetic declination applied automatically on-device (built-in World Magnetic Model — no NOAA lookup), compass-calibration status, tap-to-record skyline vertices, polar preview, and .hrz export via the share sheet — ready for N.I.N.A. and harp plan.

Getting the app

There is no store listing yet: build a debug APK yourself, one of two ways.

Path A — GitHub CI (zero setup)

Every push touching android/** or src/** builds a debug APK in the Android workflow; download the harp-debug-apk artifact from the Actions run and sideload it. Convenient, but each iteration costs a CI round-trip.

Path B — local build (fast iteration)

A one-time headless toolchain (JDK 21, Android SDK 35 command-line tools, Gradle 8.13 — no Android Studio required), then:

gradle -p android :app:assembleDebug
# -> android/app/build/outputs/apk/debug/app-debug.apk

First build is slow (Chaquopy fetches the Android wheels of the astro stack); later builds take seconds to a minute. The full setup commands, phone-transfer options (HTTP serve or wireless adb), and the on-device debugging tip (adb logcat -s python.stderr) are in android/README.md, together with the first-device test checklist.