Sample login app for Android Java will not compile
I am running Android Studio 3.1.1 on an Ubuntu linux machine. I have downloaded and installed backendless-4.5.1.jar. From the backendless console I downloaded the sample "login" app. When I try to run the sample code in Android Studio I get the following error message: "Compilation failed". The java compiler error log says the problem is in RegisterActivity.java. The specific compiler error message is: "error: cannot find symbol class AsyncCallback." In line 91 of RegisterActivity the code reads: "Backendless.UserService.register(user, new AsyncCallback<BackendlessUser>();" The AsyncCallback portion of this line of code is flagged in red. So, what can I do by myself to correct this situation?
Thank you in advance. I am a newbie and still earning the product.