Together with buttons, another extremely common form of user interaction is the text field. There comes a point in most apps where your users will need to type something; for example, a form where users need to type in their username and password.
Because the text is often related to the concept of forms, Flutter also has a subclass of TextField called TextFormField, which adds functionality for multiple text fields to work together.
In this recipe, we're going to create a login form for our stopwatch app so that we know which runner we're timing.
