How does focus traversal work for users navigating a Flutter app using a keyboard or an external switch device, and how can you control the order in which interactive elements are focused?

Focus traversal determines the order in which interactive elements, such as buttons and text fields, receive focus when a user navigates through an app using the tab key on a keyboard or an external assistive switch device rather than by touch, and Flutter automatically determines a reasonable default traversal order based on the widget tree structure, but a developer can explicitly control this order using a FocusTraversalGroup or by assigning explicit traversal priorities when the automatically determined order does not match the logical, expected reading order of the screen.

FocusTraversalGroup(
  policy: OrderedTraversalPolicy(),
  child: Column(children: [emailField, passwordField, loginButton]),
)