By the end of this chapter, the missing link between our Kotlin code and our XML layouts will be fully revealed, leaving us with the power to add all kinds of widgets and UI features to our layouts as we have done before, but this time we will be able to control them through our code.
In this chapter, we will take control of some simple UI elements, such as Button
and TextView
, and, in the next chapter, we will take things further and manipulate a whole range of UI elements.
To enable us to understand what is happening, we need to find out a bit more about the memory in an app, and two areas of it in particular – the Stack and the Heap.
In this chapter, we will cover the following topics:
Android UI elements are classes
Garbage collection
Our UI is on the Heap
More polymorphism
Nullability – val and var revisited
Casting to different types
Prepare to make your UI come to life.