SDL3 Android Manual Build – App Won’t Start

[P3RK4N]

Hi, everyone.

I'm automating the Android build process for an SDL3-based project without using Gradle. While SDL provides an Android project template, it doesn't fully cover my case, so I'm customizing it to support prebuilt native libraries and a manual build chain.

I'm using CMake with the Android NDK and toolchain to build my native code, and that part works fine. Here's a snippet:

# Shared libs are on
if(ANDROID)
    add_library(main SHARED "src/potok/main.c")
    target_link_libraries(main log SDL3::SDL3)
endif()

// main.c

// main.c
#define SDL_MAIN_USE_CALLBACKS
#include <SDL3/SDL.h>
#include <SDL3/SDL_main.h>
...
// SDL_AppInit, SDL_AppIterate, SDL_AppEvent, SDL_AppQuit implemented
// Using SDL_Renderer to clear screen with random color when screen is pressed
// Works on desktop

This builds libmain.so and libSDL3.so.

I'm using the SDL-provided android-template but with my own native libs. Key layout:

📦android-tmp
 ┣ 📂build/apk/lib/arm64-v8a/
 ┃ ┣ 📜libmain.so # Not sure how main interacts with SDL3 as they are dynamically linked
 ┃ ┗ 📜libSDL3.so
 ┣ 📂java/org/libsdl/app/
 ┃ ┣ 📜SDLActivity.java 
 ┃  ┗ ...
 ┣ 📜AndroidManifest.xml (just added missing package name: org.libsdl.app)
# Helper stuff
 ┣ 📜android.jar
 ┣ 📜keystore.jks

No changes to Java code; I only added the package attribute in the manifest.

Lastly, here are my commands that i used:

# 1. AAPT: Generate Java bindings
aapt package -f -m -J build/gen -S res -M AndroidManifest.xml -I android.jar

# 2. Compile Java (Java 17 here)
javac --release 17 -classpath android.jar -d build/obj build/gen/org/libsdl/app/*.java java/org/libsdl/app/*.java

# 3. D8 -> classes.jar
d8 build/obj/org/libsdl/app/*.class --output build/apk/classes.jar --no-desugaring --min-api 34

# 4. Final dex
d8 android.jar classes.jar --output build/apk/

# 5. AAPT: Package APK
aapt package -f -M AndroidManifest.xml -S res -I android.jar -F build/app.unsigned.apk build/apk/

# 6. Align & sign
zipalign -f -p 4 build/app.unsigned.apk build/app.aligned.apk
apksigner sign --ks keystore.jks --ks-key-alias androidkey \
  --ks-pass pass:android --key-pass pass:android \
  --out build/app.apk build/app.aligned.apk

# 7. Install
adb install -r build/app.apk

❌ Issue

The app installs, but won’t launch at all, and logcat shows no concrete errors. I suspect something might be wrong with the context which might be set differently by SDL3 scripts.

If you could help me find out in running this up, I would be grateful. Thanks!

P.S. Sorry if this is not the best place for asking, feel free to close the issue.

[madebr]

These are the commands our test/CMakeLists.txt generates to create apks of the tests,

In general, it does:

• compile all java sources and put them in jars (our cmake script creates a jar for SDL3, and a jar for each test)
• run d8 on the jar(s)
• generate a debug key using keytool
• aapt2 compile all Android resources (=files in the res/ folder)
• aapt2 link all files together (AndroidManifest.xml is an argument here)
• add all extra files to the apk zip file generated by the aapt2 link step
• run zipalign on the apk
• run apksigner on the apk

If SDL3 finds your android ndk and sdk, you can build apks of all SDL tests with the target names <testname>-apk. e.g. ninja testsprite-apk or cmake --build . --target testcontroller-apk

I'm surprised you're using aapt. It's not mentioned on the cli page. Only aapt2. The SDL tests don't need to generate Java bindings, so I don't know how to do this with the documented cli tools.

[P3RK4N]

These are the commands our test/CMakeLists.txt generates to create apks of the tests,

In general, it does:

• compile all java sources and put them in jars (our cmake script creates a jar for SDL3, and a jar for each test)
• run d8 on the jar(s)
• generate a debug key using keytool
• aapt2 compile all Android resources (=files in the res/ folder)
• aapt2 link all files together (AndroidManifest.xml is an argument here)
• add all extra files to the apk zip file generated by the aapt2 link step
• run zipalign on the apk
• run apksigner on the apk

If SDL3 finds your android ndk and sdk, you can build apks of all SDL tests with the target names <testname>-apk. e.g. ninja testsprite-apk or cmake --build . --target testcontroller-apk

I'm surprised you're using aapt. It's not mentioned on the cli page. Only aapt2. The SDL tests don't need to generate Java bindings, so I don't know how to do this with the documented cli tools.

Hey, I was using outdated guide (https://hereket.com/posts/android_from_command_line/) which worked for simple case. Upgrading it to sdl example was not successful.

Im gonna check tests to see if there is anything i could use

[madebr]

Closing since this does not appear to be an SDL issue.