Android JNI で C/C++ のポインタを Java に渡す。(C++側のソース)

NdkPointer.cpp

#include <jni.h>
#include <android/log.h>

#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG,"NdkPointer", __VA_ARGS__)

static JavaVM* jvm = nullptr;
static JNIEnv* env;

class CppClass {

public:
	void callback() {
		LOGD("!!!! callback called !!!!");
	}
};

extern "C" {

jint JNI_OnLoad(JavaVM* vm, void* reserved) {
	jvm = vm;
	vm->GetEnv((void**)&env, JNI_VERSION_1_6);
	return JNI_VERSION_1_6;
}

void Java_com_example_ndkpointer_MainActivity_nativeMethod() {
	LOGD("nativeMethod called");

	auto obj = new CppClass();

	jclass c = env->FindClass("com/example/ndkpointer/MainActivity");
	if (c == nullptr) {
		LOGD("class not found.");
		return;
	}
	jmethodID mid = env->GetStaticMethodID(c, "asyncProc", "(J)V");
	if (mid == nullptr) {
		LOGD("method not found");
		return;
	}
	env->CallStaticVoidMethod(c, mid, reinterpret_cast<jlong>(obj));

}

void Java_com_example_ndkpointer_MainActivity_callback(jlong p) {
	CppClass* obj = (CppClass*)p;
	obj->callback();
	delete obj;
}
}