All the Android UI elements are classes too
When our app is run and the setContentView method is called from the onCreate method, the layout is inflated from the XML and instances of the UI classes are loaded into memory as usable objects. They are stored in a part of the memory called the heap. The heap is managed by the Android Runtime (ART) system.
Re-introducing references
But where are all these UI objects/classes? We certainly can't see them in our code. And how on earth do we get our hands on them?
The ART inside every Android device takes care of memory allocation to our apps. In addition, it stores different types of variables in different places.
Variables that we declare and initialize in methods are stored on the area of memory known as the Stack. We can stick to our existing warehouse analogy when talking about the Stack. We already know how we can manipulate variables on the Stack with straightforward expressions. So, let's talk about the heap...