Widgets

In flutter almost everything is a widget, including the entire app. This also includes thing like alignment, padding and layout.

A widget’s main job is to provide a build() method that describes how to display the widget in terms of other, lower level widgets.

StatelessWidget

Stateless widgets are immutable, so their properties are final and can't change.

StatefulWidget

A stateful widget contains state which may change over the lifetime of the widget. A StatefulWidget instance must contain an instace of a State class.

A StatefulWidget should define a method createState() which instantiates the relevant state class (see below).

State

If you have a stateful widget class called ExampleClass, you can create a corresponding state widget like so:

class ExampleStateClass extends State<ExampleClass> {
    build()

    ...
}