Building from source

#What you need

• JDK 17
• Android SDK with platform 34 and build-tools 34.0.0
• Android NDK (any recent one) for the controller passthrough helper; without it Tandem builds without that feature
• Git

Gradle itself comes with the repository (./gradlew), and the first build downloads the rest.

#With Nix or NixOS

The repository's shell.nix provides JDK 17, the Android SDK and adb:

git clone https://github.com/ZahakJ/tandem && cd tandem
nix-shell --run './gradlew assembleDebug'

The shell also points Gradle at the SDK's own aapt2, because the one Gradle downloads is a generic Linux binary that doesn't run on NixOS.

#The controller passthrough helper

Controller passthrough (Controls) uses a small C program, app/src/padlink/padlink.c. The build compiles it for 64-bit ARM with the newest NDK in the SDK (task buildPadLink) and packs it as lib/arm64-v8a/libpadlink.so; native libraries are unpacked on install (useLegacyPackaging), so Tandem can run it through Shizuku or su. Without an NDK the build warns and leaves it out, and the feature stays hidden. To try it by hand on a device: adb shell <Tandem's lib folder>/libpadlink.so prints its usage.

#With a plain JDK and SDK

Install JDK 17 and the Android SDK (Android Studio installs both). Then tell Gradle where the SDK is, either with an environment variable:

export ANDROID_HOME="$HOME/Android/Sdk"

or with a local.properties file in the repository root (it is ignored by git):

sdk.dir=/home/you/Android/Sdk

Make sure the right SDK packages are installed:

"$ANDROID_HOME/cmdline-tools/latest/bin/sdkmanager" "platforms;android-34" "build-tools;34.0.0" "ndk;27.2.12479018"

and build:

./gradlew assembleDebug

#Where the APK goes

A debug build is signed with your computer's debug key; official releases are signed with the project's release key. Both use the same app id, so Android won't install one over the other: switching between them means uninstalling first. Uninstalling deletes Tandem's data, so back up first (Settings › Data & about › Back up).

#Installing on a device

With USB debugging (or wireless debugging) on:

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

./gradlew installDebug builds and installs in one step. To see what Tandem logs:

adb logcat -s Tandem

#Discord status

The optional Discord status (Privacy) uses Discord's Social SDK, which is proprietary, so it isn't in the repository and a plain build leaves it out: no Discord code is compiled in and the setting doesn't show. To build with it:

1. Create a Discord application in the Discord Developer Portal and enable the Social SDK for it. Under OAuth2, switch on Public Client and add the redirect discord-<application ID>:/authorize/callback, with your application's ID.

2. Download the Social SDK from the portal and copy lib/release/discord_partner_sdk.aar from it into third_party/discord/ (any folder inside it works). That folder is ignored by git; never commit the SDK.

3. Put the application ID in local.properties (or pass -Pdiscord.appId=...):

   discord.appId=123456789012345678

4. Build as usual. The build also needs the Android NDK and CMake 3.22.1, which Android Studio installs from the SDK Manager. With Nix, shell.nix adds them by itself once third_party/discord exists. Without an NDK the build leaves Discord out and says so.

With both the .aar and the ID present, the build compiles a small JNI bridge (app/src/discord) and adds the SDK's sign-in activity for the redirect. The SDK's voice-chat permissions are removed, and the build includes only the 64-bit ARM library (about 9 MB more).

#Continuous integration

Every push and pull request is built by GitHub Actions (ci.yml), and the debug APK is attached to the run as an artifact, so you can try a pull request without building it yourself. Releases are built from tags by release.yml; see Releasing.

#Building this website

The website lives in site/, and the documentation pages are generated from the Markdown in docs/ by a small script with no dependencies:

node scripts/build-docs.mjs

That writes site/docs/, and fails on a broken link between pages. To preview, serve site/ with any static file server, for example npx serve site or python3 -m http.server -d site.