Flutter下拉刷新插件liquid_pull_to_refresh的使用

Liquid Pull To Refresh 是一个用于Flutter应用程序的自定义下拉刷新指示器，它具有美观的设计，灵感来自于Ramotion Pull Down to Refresh。你可以通过下面的内容了解如何安装、配置以及在你的项目中使用这个插件。

安装

1. Depend on it

在pubspec.yaml文件中添加依赖：

dependencies:
  liquid_pull_to_refresh: ^3.0.1

2. Install it

可以通过命令行安装依赖包：

• 使用 pub:

  $ pub get
  

• 使用 flutter:

  $ flutter packages get
  

3. Import it

在Dart代码中导入包：

import 'package:liquid_pull_to_refresh/liquid_pull_to_refresh.dart';

使用方法

要将此自定义刷新指示器添加到你的Flutter应用中，只需要简单地将ListView或GridView包装在LiquidPullToRefresh组件内，并提供onRefresh参数作为刷新回调函数即可。

例如：

LiquidPullToRefresh(
  key: _refreshIndicatorKey, // 如果需要可以添加key
  onRefresh: _handleRefresh, // 刷新回调
  child: ListView(), // 滚动视图
);

如果你不希望子组件有透明度过渡效果，可以设置showChildOpacityTransition: false。

以下是关于LiquidPullToRefresh类的一些重要属性：

示例Demo

以下是一个完整的示例demo，展示了如何使用liquid_pull_to_refresh插件创建一个带有下拉刷新功能的应用程序。

import 'dart:async';
import 'dart:math';

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

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Liquid Pull To Refresh'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, this.title}) : super(key: key);

  final String? title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();
  final GlobalKey<LiquidPullToRefreshState> _refreshIndicatorKey =
      GlobalKey<LiquidPullToRefreshState>();

  static int refreshNum = 10; // 刷新时变化的数字
  Stream<int> counterStream =
      Stream<int>.periodic(const Duration(seconds: 3), (x) => refreshNum);

  ScrollController? _scrollController;

  @override
  void initState() {
    super.initState();
    _scrollController = ScrollController();
  }

  static final List<String> _items = <String>[
    'A',
    'B',
    'C',
    'D',
    'E',
    'F',
    'G',
    'H',
    'I',
    'J',
    'K',
    'L',
    'M',
    'N'
  ];

  Future<void> _handleRefresh() {
    final Completer<void> completer = Completer<void>();
    Timer(const Duration(seconds: 3), () {
      completer.complete();
    });
    setState(() {
      refreshNum = Random().nextInt(100);
    });
    return completer.future.then<void>((_) {
      ScaffoldMessenger.of(_scaffoldKey.currentState!.context).showSnackBar(
        SnackBar(
          content: const Text('Refresh complete'),
          action: SnackBarAction(
            label: 'RETRY',
            onPressed: () {
              _refreshIndicatorKey.currentState!.show();
            },
          ),
        ),
      );
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _scaffoldKey,
      appBar: AppBar(
        title: Stack(
          children: [
            const Align(
              alignment: Alignment(-1.0, 0.0),
              child: Icon(Icons.reorder),
            ),
            Align(
              alignment: const Alignment(-0.3, 0.0),
              child: Text(widget.title!),
            ),
          ],
        ),
      ),
      body: LiquidPullToRefresh(
        key: _refreshIndicatorKey,
        onRefresh: _handleRefresh,
        showChildOpacityTransition: false,
        child: StreamBuilder<int>(
          stream: counterStream,
          builder: (context, snapshot) {
            return ListView.builder(
              padding: kMaterialListPadding,
              itemCount: _items.length,
              controller: _scrollController,
              itemBuilder: (BuildContext context, int index) {
                final String item = _items[index];
                return ListTile(
                  isThreeLine: true,
                  leading: CircleAvatar(child: Text(item)),
                  title: Text('This item represents $item.'),
                  subtitle: Text(
                      'Even more additional list item information appears on line three. ${snapshot.data}'),
                );
              },
            );
          },
        ),
      ),
    );
  }
}

这个示例创建了一个简单的Flutter应用，其中包含一个带有字母项的列表视图。当用户执行下拉刷新操作时，会触发_handleRefresh方法，该方法更新refreshNum并显示一个Snackbar通知用户刷新完成。