ci: build simple Android SDL app using gradle

android-project/app/jni/src/CMakeLists.txt

@@ -1,13 +1,29 @@
 cmake_minimum_required(VERSION 3.6)
 
-project(MY_APP)
+project(my_app)
 
-find_library(SDL3 SDL3)
+if(NOT TARGET SDL3::SDL3)
+    find_package(SDL3 CONFIG)
+endif()
 
-add_library(main SHARED)
+if(NOT TARGET SDL3::SDL3)
+    find_library(SDL3_LIBRARY NAMES "SDL3")
+    find_path(SDL3_INCLUDE_DIR NAMES "SDL3/SDL.h")
+    add_library(SDL3::SDL3 UNKNOWN IMPORTED)
+    set_property(TARGET SDL3::SDL3 PROPERTY IMPORTED_LOCATION "${SDL3_LIBRARY}")
+    set_property(TARGET SDL3::SDL3 PROPERTY INTERFACE_INCLUDE_DIRECTORIES "${SDL3_INCLUDE_DIR}")
+endif()
 
-target_sources(main PRIVATE YourSourceHere.c)
-
-target_link_libraries(main SDL3)
+if(NOT TARGET SDL3::SDL3)
+    message(FATAL_ERROR "Cannot find SDL3.
 
+Possible ways to fix this:
+- Use a SDL3 Android aar archive, and configure gradle to use it: prefab is required.
+- Add add_subdirectory(path/to/SDL) to your CMake script, and make sure a vendored SDL is present there.
+")
+endif()
 
+add_library(main SHARED
+    YourSourceHere.c
+)
+target_link_libraries(main PRIVATE SDL3::SDL3)

android-project/app/jni/src/YourSourceHere.c

@@ -0,0 +1,26 @@
+#include <SDL3/SDL.h>
+#include <SDL3/SDL_main.h>
+
+/* !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! */
+/*                                                       */
+/* Remove this source, and replace with your SDL sources */
+/*                                                       */
+/* !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! */
+
+int main(int argc, char *argv[]) {
+    (void)argc;
+    (void)argv;
+    if (SDL_Init(SDL_INIT_EVENTS | SDL_INIT_VIDEO) < 0) {
+        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "SDL_Init failed (%s)", SDL_GetError());
+        return 1;
+    }
+
+    if (SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_INFORMATION, "Hello World",
+                                 "!! Your SDL project successfully runs on Android !!", NULL) < 0) {
+        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "SDL_ShowSimpleMessageBox failed (%s)", SDL_GetError());
+        return 1;
+    }
+
+    SDL_Quit();
+    return 0;
+}