The focus manager

This article explains how to control where keyboard input is directed. If you
are implementing an application that uses a physical keyboard, such as most
desktop and web applications, this page is for you. If your app won’t be used
with a physical keyboard, you can skip this.

Overview

Flutter comes with a focus system that directs the keyboard input to a
particular part of an application. In order to do this, users “focus” the input
onto that part of an application by tapping or clicking the desired UI element.
Once that happens, text entered with the keyboard flows to that part of the
application until the focus moves to another part of the application.  Focus can
also be moved by pressing a particular keyboard shortcut, which is typically
bound to the Tab key, so it is sometimes called “tab traversal”.