Crash in android when using android context in CPP layer

Question

I am using NDK with cocos2dx. In main.cpp, I have the following method.

       void Java_org_cocos2dx_lib_Cocos2dxRenderer_nativeInit(JNIEnv*  env, 
           jobject thiz, jint w, jint h)

Is it possible to assign jobject thiz to another object and use in cpp? Just like this:-

         static jobject context = NULL;
         void Manager::SetJobject(jobject object)
         {
           context = object;
         }
          .............
         // in some other class
         //if platform == ANDROID
           connectToSomeThirdParty(context, key );

I tried this , but I got crash. Crash log is shown below:

10-01 11:38:13.228: E/dalvikvm(5828): JNI ERROR (app bug): attempt to use stale local reference 0x1e200001
10-01 11:38:13.228: E/dalvikvm(5828): VM aborting
10-01 11:38:13.228: A/libc(5828): Fatal signal 6 (SIGABRT) at 0x000016c4 (code=-6), thread 5857 (Thread-577)

Thanks in advance.

score 0 · Answer 1 · edited May 23 '17 at 11:44

Try global references. Please see:

Global and Local References (Oracle about JNI)

What is 'JNI Global reference' (at StackOverflow)

"A JNI global reference is a reference from "native" code to a Java object managed by the Java garbage collector." "JNI global references are prone to memory leaks."

It is more or less safe to store the application context, storing a reference to an Activity during initialization is almost definitely a memory leak (normally after a screen turn a new Activity is created and the old one is garbage-collected). If you do not really want to care about freeing the resources, consider a refactoring like:

class MyClass {
    static Context mContext;
    MyClass(Context c) {
        mContext = c.getApplicationContext(); // or just c
    }
    public static myFunc(int arg) {
        myFuncNative(mContext, arg);
    }
    private static native myFuncNative(Context c, int a);
}

It is still recommended to keep the application context.

People do use references to activities, but usually such references are set in onResume() and cleared in onPause().

Crash in android when using android context in CPP layer

1 Answers1