Function SystemEventHandler

Core/ClientSMLSWIG/Java/JavaCallbackByHand.h:850–882

This is the C++ handler which will be called by clientSML when the event fires. Then from here we need to call back to Java to pass back the message.

// This is the C++ handler which will be called by clientSML when the event fires.
// Then from here we need to call back to Java to pass back the message.
static void SystemEventHandler(sml::smlSystemEventId id, void* pUserData, sml::Kernel* pKernel)
{
    // The user data is the class we declared above, where we store the Java data to use in the callback.
    JavaCallbackData* pJavaData = (JavaCallbackData*)pUserData ;
    
    // Now try to call back to Java
    JNIEnv* jenv = pJavaData->GetEnv() ;
    
    // We start from the Java object whose method we wish to call.
    jobject jobj = pJavaData->m_HandlerObject ;
    jclass cls = jenv->GetObjectClass(jobj) ;
    
    if (cls == 0)
    {
        printf("Failed to get Java class\n") ;
        return ;
    }
    
    // Look up the Java method we want to call.
    // The method name is passed in by the user (and needs to match exactly, including case).
    // The method should be owned by the m_HandlerObject that the user also passed in.
    // Any slip here and you get a NoSuchMethod exception and my Java VM shuts down.
    jmethodID mid = jenv->GetMethodID(cls, pJavaData->m_HandlerMethod.c_str(), "(ILjava/lang/Object;Lsml/Kernel;)V") ;
    
    if (mid == 0)
    {
        printf("Failed to get Java method\n") ;
        return ;
    }
    
    // Make the method call.
    jenv->CallVoidMethod(jobj, mid, (int)id, pJavaData->m_CallbackData, pJavaData->m_KernelObject);
}

// This is the hand-written JNI method for registering a callback.
// I'm going to model it after the existing SWIG JNI methods so hopefully it'll be easier to patch this into SWIG eventually.