What is FutureBuilder and StreamBuilder?

 Both are widgets to handle asynchronous data.

FutureBuilder – For one-time data (Future)

FutureBuilder(
  future: getData(),
  builder: (context, snapshot) {
    if (snapshot.hasData) return Text(snapshot.data);
    return CircularProgressIndicator();
  },
);

StreamBuilder – For continuous data (Stream)

StreamBuilder(
  stream: counterStream,
  builder: (context, snapshot) {
    if (snapshot.hasData) return Text('${snapshot.data}');
    return CircularProgressIndicator();
  },
);