Creating object of c++ class in Activity when using C++ with android NDK

First of all, Activity is a controller from MVC viewpoint, an activity gets destroyed when the screen orientation changes from, say, vertical to horizontal. First create a class able to outlive the activities and use the native resources from there.

I assume you know how to create and invoke native functions, and know how to create a C++ object. I also assume you know what

#ifdef __cplusplus
extern "C" {
#endif

and

#ifdef __cplusplus
}
#endif

do in a .h file (they allow functions compiled with C++ (not member functions, just functions) be visible from C).

Now, calling C++ object instance methods from Java is basically the same as calling C++ object instance methods from plain C. Instead of doing

myObject.myMethod(arg1,arg2, ...)

you will have to do

callMyMethod(myObjHandle, arg1, arg2, ...)

where myObjHandle may be the native address of the C++ object converted into an int.

You, of course, will have to care about deleting that C++ object -- Java has no means to know that some integer value must be passed to C++ to either delete or delete[] it.

And a good news for you is that the same threads are used for Java and native code.

To call the C++ method from Activity you need to declare that method as 'native'.

//MultiPlayerJNI.java
public static native void onNetworkDataReceived(int index);

//MultiPlayerJNI.h
void Java_com_example_game_MultiPlayerJNI_onNetworkDataReceived(JNIEnv *env, jobject thiz, jint spIndex);

//MultiPlayerJNI.cpp
void Java_com_example_game_MultiPlayerJNI_onNetworkDataReceived(JNIEnv *env, jobject thiz, jint spIndex){
DebugLog("JNI onNetworkDataReceived");

if(MultiplayerJNI::getInstance()->multiGameController != NULL){
    MultiPlayerJNI::getInstance()->multiGameController->onNetworkDataReceived(spIndex);
}else if(MultiPlayerJNI::getInstance()->singleGameController != NULL){
    MultiPlayerJNI::getInstance()->singleGameController->onNetworkDataReceived(spIndex);


   }
}

To call Java method from C++

//MultiPlayerJNI.h
void getTableInfo();

//MultiPlayerJNI.cpp
void MultiPlayerJNI::getTableInfo(){
DebugLog("MultiPlayerJNI::getTableInfo()");
 JniMethodInfo t;
    if (JniHelper::getStaticMethodInfo(t
                                , "com/example/game/MultiPlayerJNI"
                                , "getTableInfo"
                                , "()V"))
        {
         t.env->CallStaticVoidMethod(t.classID,t.methodID);
            t.env->DeleteLocalRef(t.classID);
            }
}
//MultiPlayerJNI.java
public static void getTableInfo(){

}

I would suggest creating Singleton JNI classes for Java and CPP part.

I sometimes use C or C++ in my Android Project. But create Java object in C/C++ source code. If you will create C++ class in your Java source code, maybe ...

( I understood what do you want and only I give an idea. Maybe create Java Object in C++ source code)

this is my example;(In example deployed Java object in native code.)

// JAVA CODE

public class mActivity extends Activity{

public native Object get();
public native void set(Object data);
}

// C CODE

typedef struct data_type
{
    jobject data;
    struct data_type* next;
}DATA_TYPE;

jobject Java_com_example_nativequeue_TestActivity_get(JNIEnv* env, jobject thiz)
{
    if(HEADER != NULL){
        jobject result = HEADER->data;
        --data_struct_size;
        return result;
    }

    if(HEADER->next != NULL)
        HEADER = HEADER->next;


    return NULL;
}

void Java_com_example_nativequeue_TestActivity_set(JNIEnv* env, jobject thiz, jobject data)
{
    jobject new_data = (*env)->NewGlobalRef(env, data);
    if(new_data == NULL){
        return;
    }

    NEW = (DATA_TYPE*)malloc(sizeof(DATA_TYPE));
    NEW->data = new_data;
    NEW->next = NULL;

    if(HEADER == NULL){
        HEADER = NEW;
        FOOTER = HEADER;
    }else{
        FOOTER->next = NEW;
        FOOTER = NEW;
    }

    ++data_struct_size;

}