Nrthugu

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See edit for latest problem. I am trying to pass a Vector3 value from my cpp library to my java activity. I am able to do it vice versa, but cannot seem to find a way to go cpp to java. Anyone mine helping me out with this? I am receving this error: undefined reference to 'jni_createjavavm'

JavaVM *jvm;       /* denotes a Java VM */

JNIEnv *env;       /* pointer to native method interface */

JavaVMInitArgs vm_args; /* JDK/JRE 6 VM initialization arguments */

JavaVMOption* options = new JavaVMOption[1];

options[0].optionString = "-Djava.class.path=/usr/lib/java";

vm_args.version = JNI_VERSION_1_6;

vm_args.nOptions = 1;

vm_args.options = options;

vm_args.ignoreUnrecognized = false;

/* load and initialize a Java VM, return a JNI interface

 * pointer in env */

JNI_CreateJavaVM(&jvm, &env, &vm_args);

delete options;

/* invoke the Main.test method using the JNI */

jclass cls = env->FindClass("MenuActivity");

jmethodID mid = env->GetStaticMethodID(cls, "Test", "(I)V");

env->CallStaticVoidMethod(cls, mid);

/* We are done. */

jvm->DestroyJavaVM();

Nov 11 2018 @2031 UTC+9 | EDIT: New Problem.. Crashes with java_class == NULL.

JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM *vm, void *reserved) {

//Some Other Code Not Regarding JVM



JNIEnv *env;

vm->AttachCurrentThread(&env, NULL);

jclass cls = env->FindClass("MenuActivity");

jmethodID mid = env->GetStaticMethodID(cls, "Test", "(I)V");

env->CallStaticVoidMethod(cls, mid);

return JNI_VERSION_1_6;

}

On Android, there is no JNI_CreateJavaVM(). The apps run in JVM which is essential to access system APIs and services.

The callbacks from native code to the Java part of the app use the JNIEnv * that must belong to the current thread.

If this runs on a Java thread, the JNIEnv is received as the first parameter by the native method. You can call back to Java from a native thread, too. But then, you must attach the thread to JVM. AttachCurrentThread() accepts JavaVM * which can be stored as a global in your native code. You can obtain it in JNI_OnLoad() or derive it from JNIEnv with GetJavaVM().

Each native thread that is attached, must be detached on termination. The best practice is to use pthread_key_create() to define a destructor function that will be called before the thread exits.

You can read more explanations in the Android JNI tips article.