Flutter: 下拉刷新，上拉加载更多

import 'package:flutter/material.dart';
import 'package:english_words/english_words.dart';

void main() => runApp(Myapp());

class Myapp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(home: MyHome());
  }
}

class MyHome extends StatefulWidget {
  @override
  _MyHomeState createState() => _MyHomeState();
}

class _MyHomeState extends State<MyHome> {
  final _suggestions = <WordPair>[];
  bool _loading = true;
  ScrollController _strollCtrl = ScrollController();

  Future<void> _getData() async {
    await Future.delayed(Duration(seconds: 1));
    setState(() {
      _suggestions.addAll(generateWordPairs().take(15));
      _loading = false;
    });
  }

  @override
  void initState() {
    _getData();
    _strollCtrl.addListener(() {
      if (_strollCtrl.position.pixels == _strollCtrl.position.maxScrollExtent) {
        if (!_loading) {
          setState(() {
            _loading = true;
          });
        }
        _getData();
      }
    });
    super.initState();
  }

  @override
  void dispose() {
    _strollCtrl.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('ListView'),
      ),
      body: Stack(
        children: <Widget>[
          _loading
              ? Center(
                  child: Column(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: <Widget>[
                      RefreshProgressIndicator(
                        semanticsLabel: 'loading more..',
                        semanticsValue: 'loading more..',
                      ),
                      Text(
                        '加载中...',
                        style: Theme.of(context).textTheme.title,
                      ),
                    ],
                  ),
                )
              : Container(),
          // 下拉加载更多组件
          RefreshIndicator(
            onRefresh: () async {
              _suggestions.clear();
              return _getData();
            },
            child: ListView.builder(
              physics: const AlwaysScrollableScrollPhysics(), // 确保滚动视图始终可滚动
              controller: _strollCtrl,
              itemCount: _suggestions.length,
              itemBuilder: (context, i) {
                return ListTile(
                  leading: Text('${(i + 1).toString()}'),
                  title: Text('${_suggestions[i].asPascalCase}'),
                  trailing: Icon(Icons.event),
                );
              },
            ),
          ),
        ],
      ),
    );
  }
}