Streambuilder is a widget that listens to events emitted by a stream, and whenever an event is emitted, it rebuilds its descendants. Like the FutureBuilder widget, which we have seen in Chapter 7, The Future Is Now: Introduction to Asynchronous Programming, StreamBuilder makes it extremely easy to build reactive user interfaces that update every time new data is available.
In this recipe, we will update the text on the screen with StreamBuilder. This is very efficient compared to the update that happens with a setState method and its build call, as only the widgets contained in StreamBuilder are actually redrawn.
