How to access an element (or an Activity method) from the Application class?

Question

Java

Good evening, I'm still new to Android. I am developing an application that receives messages from a computer using the singleton principle. How do I access an element (eg TextView) in a running Activity, the Application class acts as a singleton?

Answer 1

in the designer, add a specific id to the desired TextView (for example, myTextView). Next, add the following text to the end of the onCreate() method.
Further work is already underway with myTextView.