Not being able to understand the flutter docs - flutter

Question

I was referencing to the Flutter Docs, but I am not able to correctly read them. What I am trying to say is that I am not able to correctly understand them. I am having questions like "How would I know if a property accepts Widget or double or MaterialStateProperty?"
I was trying to understand the elevation property under ButtonStyle class under ButtonStyleButton class. It is written as:
elevation → MaterialStateProperty<double?>?
The elevation of the button's Material.
I can't understand this syntax. What will be the input of elevation if I am defining the custom ButtonClassButton class as following:
class RoundIconButton extends StatelessWidget {
const RoundIconButton({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return ButtonStyleButton(
onPressed: () {},
style: ButtonStyle(
elevation: ?????????????,
),
);
}
}

Answer 1

The MaterialState enum provides interactive states that some of the Material widgets can take on when receiving input from the user. The MaterialStateProperty<T> class is an interface for classes that resolve to a value of type T based on a widget's interactive "state".
To provide more clarification, please refer the Static Methods under MaterialStateProperty class here.
If you have a single value for all states (say 10.0 as the double value), you can set the elevation as follows:
class RoundIconButton extends StatelessWidget {
const RoundIconButton({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return ButtonStyleButton(
onPressed: () {},
style: ButtonStyle(
elevation: MaterialStateProperty.all(10),
),
);
}
}