The RefreshIndicator widget in Flutter provides a standard way to add the "swipe to refresh" functionality to a scrollable widget, typically a ListView, GridView, or CustomScrollView. It's commonly used when you want users to pull down on the screen to trigger a refresh action.

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyRefreshIndicator(),
    );
  }
}

class MyRefreshIndicator extends StatefulWidget {
  @override
  _MyRefreshIndicatorState createState() => _MyRefreshIndicatorState();
}

class _MyRefreshIndicatorState extends State<MyRefreshIndicator> {
  List<String> items = List.generate(20, (index) => 'Item ${index + 1}');
  GlobalKey<RefreshIndicatorState> refreshKey = GlobalKey<RefreshIndicatorState>();

  Future<void> refreshList() async {
    // Simulating data fetching delay with Future.delayed
    await Future.delayed(Duration(seconds: 2));

    // Add new items or update the list here
    setState(() {
      items = List.generate(20, (index) => 'Refreshed Item ${index + 1}');
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('RefreshIndicator Example')),
      body: RefreshIndicator(
        key: refreshKey,
        onRefresh: refreshList,
        child: ListView.builder(
          itemCount: items.length,
          itemBuilder: (BuildContext context, int index) {
            return ListTile(
              title: Text(items[index]),
              // Add onTap or other interactions as needed
            );
          },
        ),
      ),
    );
  }
}

In this example, a RefreshIndicator wraps a ListView.builder. The onRefresh callback is called when the user performs the swipe-down action to refresh the list. In this case, the refreshList function simulates the refresh by replacing the existing list items with new ones after a delay.