[flutter-chat-demo]home.dart

Container(
  child: StreamBuilder(
    stream: Firestore.instance.collection('users').limit(_limit).snapshots(),
    builder: (context, snapshot) {
      if (!snapshot.hasData) {
        return Center(
          child: CircularProgressIndicator(
			valueColor: AlwaysStoppedAnimation<Color>(themeColor),
          ),
        );
      } else {
        return ListView.builder(
          padding: EdgeInsets.all(10.0),
          itemBuilder: (context, index) => buildItem(context, snapshot.data.documents[index]),
          itemCount: snapshot.data.documents.length,
        );
      }
    },
  ),
),