Retrieve the Java instance of the Android activity class.
Defined in <SDL3/SDL_system.h>
void * SDL_GetAndroidActivity(void);(void *) Returns the jobject representing the instance of the Activity class of the Android application, or NULL on failure; call SDL_GetError() for more information.
The prototype of the function in SDL's code actually declares a void* return type, even if the implementation returns a jobject. The rationale being that the SDL headers can avoid including jni.h.
The jobject returned by the function is a local reference and must be released by the caller. See the PushLocalFrame() and PopLocalFrame() or DeleteLocalRef() functions of the Java native interface:
https://docs.oracle.com/javase/1.5.0/docs/guide/jni/spec/functions.html
It is safe to call this function from any thread.
This function is available since SDL 3.2.0.
#include <SDL3/SDL.h> #include <jni.h> // This example requires C++ and a custom Java method named "void showHome()" // Calls the void showHome() method of the Java instance of the activity. void showHome(void) { // retrieve the JNI environment. JNIEnv* env = (JNIEnv*)SDL_GetAndroidJNIEnv(); // retrieve the Java instance of the SDLActivity jobject activity = (jobject)SDL_GetAndroidActivity(); // find the Java class of the activity. It should be SDLActivity or a subclass of it. jclass clazz(env->GetObjectClass(activity)); // find the identifier of the method to call jmethodID method_id = env->GetMethodID(clazz, "showHome", "()V"); // effectively call the Java method env->CallVoidMethod(activity, method_id); // clean up the local references. env->DeleteLocalRef(activity); env->DeleteLocalRef(clazz); // Warning (and discussion of implementation details of SDL for Android): // Local references are automatically deleted if a native function called // from Java side returns. For SDL this native function is main() itself. // Therefore references need to be manually deleted because otherwise the // references will first be cleaned if main() returns (application exit). }