Testing on a physical Android device

The fastest inner loop for this app is building the debug APK and installing it straight onto a real device over USB (an Android phone, or an Android-based DAP like the FiiO M33). This is quicker than nix run .#emulate and tests real networking to your MPD server.

One-time device setup

Enable Developer Options: Settings → About phone → tap Build number seven times.
Enable USB debugging: Settings → System → Developer options → USB debugging.
Use a data-capable USB cable and plug the device directly into the machine. Many cables are charge-only — if the device never appears in lsusb, suspect the cable or the USB mode first.
Unlock the device screen. The "Allow USB debugging?" authorization dialog only appears while unlocked — this is the usual reason "no popup shows up". Tap Allow and check Always allow from this computer.

NixOS note (this machine)

adb is provided by the dev shell (nix develop). On this NixOS host it talks to devices without needing programs.adb.enable, custom udev rules, or an adbusers group: a plugged-in, authorized device shows up directly as device.

If a device instead shows as:

unauthorized → you haven't accepted the on-device prompt yet (unlock the screen and tap Allow).
no permissions → then you'd need udev rules; add programs.adb.enable = true; and your user to the adbusers group in the NixOS config, nixos-rebuild switch, re-login, and adb kill-server. (Not currently needed here.)

Verify the device is connected

adb devices -l          # should list the device as `device` (not unauthorized)
adb shell getprop ro.product.model

If adb devices is empty, check lsusb for the device (Pixels show as Google Inc. … / vendor 18d1), then re-check the cable and USB debugging.

Build, install, launch

From the repo root, inside nix develop:

./gradlew assembleDebug
adb install -r app/build/outputs/apk/debug/app-debug.apk
adb shell am start -n ca.ksamad.musicremote/.MainActivity   # optional auto-launch

-r reinstalls over the existing app keeping its data (so persisted connection settings survive). To simulate a clean first run:

adb shell pm clear ca.ksamad.musicremote

Screenshots

adb exec-out screencap -p > screenshot.png

Troubleshooting

"failed to connect to :" — the device can't reach the MPD server. Check the device is on the same WiFi/LAN as the server. A common gotcha: WiFi is off on a portable DAP, so adb shell ip route shows no route and adb shell ping <server> returns "Network is unreachable".
App looks stale after changes — reinstall the APK; restarting the device or emulator alone does not update the installed app.

Wireless alternative (no cable)

Android 11+ supports wireless debugging (Developer options → Wireless debugging → Pair device with pairing code), then on the host:

adb pair <ip>:<pair-port>      # enter the code shown on-device
adb connect <ip>:<debug-port>

This needs no cable and no udev rules; the device must share your LAN.

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