How to get the native activity class name

So I need to call a function in java from c++.
To do that i need the class that inherits from the native activity, in my case that class is called theReader.

I’m using this code:
const char* NativeActivityClassName = “theReader”;

void AdmobHelper::hideAd(){
cocos2d::JniMethodInfo t;
if (cocos2d::JniHelper::getStaticMethodInfo(t
, NativeActivityClassName
, “hideAD”
, “()V”))
{
t.env->CallStaticVoidMethod(t.classID, t.methodID);
t.env->DeleteLocalRef(t.classID);
}
}

But apparently it doesn’t find the class. What is the correct path for that class?