Android

Technical information

Flax is compiled for Linux platform using Android NDK and build with Android SDK. Supported are system version Android 7 or newer (platform API level 24). Flax uses Vulkan for rendering graphics on Android (min. Vulkan 1.0).

Android Setup

Follow these steps to setup your development PC for building game for Android platform. In case of problems, please follow official documentation of Android platform.

• Download and install Android Studio (https://developer.android.com/studio)
  • Install Android SDK within Android Studio setup.
  • Set ANDROID_HOME env var to SDK location (typically C:\Users\USERNAME\AppData\Local\Android\android-studio\sdk on Windows)
• Install NDK
  • via Android SDK Manager: Android SDK -> SDK Tools -> NDK (side by side)
  • or manually via https://developer.android.com/ndk/downloads/index.html and set ANDROID_NDK env var to install location
• Install Java
  • use in-built from Android Studio: set JAVA_HOME env var to <android-studio>\jbr
  • or download manually from https://jdk.java.net/19 and set env var JAVA_HOME to jdk root folder
• Install .Net Android Workload
  • Run dotnet workload install android via command line
  • More info: https://learn.microsoft.com/en-us/dotnet/core/tools/dotnet-workload-install
• (when using Flax from Launcher) Install Android Platform Tools for Editor installation via Flax Launcher

Troubleshooting

• Ensure to accept software licenses from Android SDK
• Verify that environment variables are properly set:
  • On Windows: echo %ANDROID_HOME%, echo %JAVA_HOME%
  • On Linux/Mac: echo $ANDROID_HOME, echo $JAVA_HOME
• If you're getting the error Missing NET SDK runtime for Android ARM64. then install Android workload for dotnet (as mentioned above). It contains .Net libs and runtime for Android required to run C#.

Build options

See Game Cooker window.

Property	Description
Output	The built game output folder (relative to the project).
Show Output	If checked, after building the output folder will be shown in an Explorer.
Configuration Mode	Game building mode. Possible options: Option Description Release The release build ready for shipment. Debug The debug build for testing and profiling. Most of the code optimizations are disabled for the best debugging experience. Development The development build for testing and profiling but is more optimized for runtime than Debug build.

Platform settings

See Android Platform Settings asset.

Property	Description
Package Name	The application package name (eg. com.company.product). Custom tokens: ${PROJECT_NAME}, ${COMPANY_NAME}.
Version Code	The application version code (eg. 1, 12, 123).
Minimum API Level	The minimum Android API level (eg. 20, 28, 34).
Target API Level	The target Android API level (eg. 20, 28, 34).
Permissions	The application permissions list (eg. android.media.action.IMAGE_CAPTURE). Added to the generated manifest file.
Default Orientation	The default screen orientation.
Textures Quality	The output textures quality (compression).
Override Icon	Custom icon texture to use for the application (overrides the default one).

C++ Debugging

• Install C++ Android development tools via Visual Studio Installer
• Build game for android to .apk and install it on the device
• Regenerate scripts projects files
• Set startup project to one named Android
• Edit that project properties: Debugging -> Package To Launch set your apk path in Package to Launch and set Additional Symbol Search Paths to game cooker output location folder with libFlaxGame.so file for the target arch ARM64 (<output>/app/jniLibs/arm64-v8a)
• Run the Android project with a debugger on an device

Optionally you can install apk manually and attach to it with

• Use Debug -> Attach to Android Process
• Once debugger is attached you can insert breakpoints and debug the game code

To fix some problems with gdb debugger inside Visual Studio do:

• Add environment variable on Windows HOME=C:/Users/yourusername where yourusername is your Windows username
• Restart Visual Studio (if opened)
• Create .gdbinit file in that HOME directory with the contents: handle SIGXCPU SIG33 SIG35 SIG36 SIGPWR nostop noprint

Android adb logs collecting

Debug and Devlopment builds are using low-level Android logger to output engine and game logs directly to the adb. Use .\adb.exe -d logcat Flax:I *:S to listen for game logs on device.

Vulkan debugging

• Build Debug build
• Copy libVkLayer_khronos_validation.so (optionally other validation libs) from NDK/sources/third_party/vulkan/src/build-android/jniLibs/arm64-v8a to output Gradle project libs folder (<output>/app/jniLibs/arm64-v8a)
• Monitor adb output log with Vulkan Validation layer logs
• Note that game performance will be lower (esp. CPU) due to additional validation of the GPU commands

Additional notes

• Flax exposes Gamepad for Android device at index 0 which can be used to vibrate the device or read the Back key pressed by the user during gameplay
• To enable device vibrations add android.permission.VIBRATE to the permissions list in Android Platform Settings asset
• To enable device network state reading add android.permission.ACCESS_NETWORK_STATE to the permissions list in Android Platform Settings asset