Getting the results from a dialog

This recipe shows an alternative way of awaiting some data from another screen, which was shown in the previous recipe, but this time, instead of using a full-sized page, we will use a dialog box: actually dialogs behave just like routes that can be await-ed.

An AlertDialog can be used to show pop-up screens that typically contain some text and buttons, but could also contain images or other widgets. AlertDialogs may contain a title, some content, and actions. The actions property is where you ask for the user's feedback (think of "save," "delete," or "accept").

There are also design properties such as elevation or background, shape or color, that help you make an AlertDialog well integrated into the design of your app.

In this recipe, we'll perform the same actions that we implemented in the previous recipe, Turning navigation routes into asynchronous functions. We will ask the user to choose a color in the dialog...