FlutterListView 列表高级功能 ( RefreshIndicator 下拉刷新组件 )

Posted 2021-09-11 韩曙亮

文章目录

• 一、下拉刷新组件
• 二、下拉刷新代码示例
• 三、相关资源

一、下拉刷新组件

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使用 Flutter 提供的 RefreshIndicator 组件 , 可以实现下拉刷新的功能 ;

使用 RefreshIndicator 组件包裹 ListView 组件 ;

在 RefreshIndicator 构造函数中 , 设置 onRefresh 参数 , 为其设置其下拉刷新回调事件 , 当用户下拉刷新时 , 会回调该方法 ;

onRefresh 参数原型如下 , 是一个 RefreshCallback 类型的对象 ;

final RefreshCallback onRefresh;

RefreshCallback 类型是一个返回值为 Future 的方法 ;

typedef RefreshCallback = Future<void> Function();

RefreshIndicator 构造函数原型 :

/// The signature for a function that's called when the user has dragged a
/// [RefreshIndicator] far enough to demonstrate that they want the app to
/// refresh. The returned [Future] must complete when the refresh operation is
/// finished.
///
/// Used by [RefreshIndicator.onRefresh].
typedef RefreshCallback = Future<void> Function();

class RefreshIndicator extends StatefulWidget {
  const RefreshIndicator({
    Key? key,
    required this.child,
    this.displacement = 40.0,
    this.edgeOffset = 0.0,
    required this.onRefresh,
    this.color,
    this.backgroundColor,
    this.notificationPredicate = defaultScrollNotificationPredicate,
    this.semanticsLabel,
    this.semanticsValue,
    this.strokeWidth = 2.0,
    this.triggerMode = RefreshIndicatorTriggerMode.onEdge,
  })

  /// A function that's called when the user has dragged the refresh indicator
  /// far enough to demonstrate that they want the app to refresh. The returned
  /// [Future] must complete when the refresh operation is finished.
  final RefreshCallback onRefresh;
}

二、下拉刷新代码示例

---

import 'package:flutter/material.dart';

var NAMES = [ '宋江', '卢俊义', '吴用', '公孙胜', '关胜',
  '林冲', '秦明', '呼延灼', '花荣', '柴进',
  '李应', '朱仝', '鲁智深', '武松', '董平',
  '张清', '杨志', '徐宁', '索超', '岱宗',
  '刘唐', '李逵', '史进', '穆弘' '雷横' ];

/// ListView 垂直列表 , RefreshIndicator  下拉刷新
void main() {
  runApp(MyApp());
}

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

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

class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    /// 材料设计主题
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          /// 标题组件
          title: Text("ListView 示例"),
        ),

        /// 列表组件
        body: RefreshIndicator(
          onRefresh: _onRefresh,
          child: ListView(
            children: _buildList(),
          ),
        ),
      ),
    );
  }

  /// 下拉刷新回调方法
  Future<Null> _onRefresh() async {
    /// 强制休眠 1 秒
    await Future.delayed(Duration(seconds: 1));

    /// 更新状态
    setState(() {
      /// 将 List 元素翻转
      NAMES = NAMES.reversed.toList();
    });
    return null;
  }

  /// 创建列表
  List<Widget> _buildList(){
    /// 遍历 NAMES 数组
    /// 调用 map 方法遍历数组元素
    return NAMES.map((name) => _generateWidget(name)).toList();
  }

  Widget _generateWidget(name){
    return Container(
      height: 80,
      margin: EdgeInsets.only(bottom: 5),
      alignment: Alignment.center,
      decoration: BoxDecoration(color: Colors.black),
      child: Text(
        name,
        style: TextStyle(
            color: Colors.yellowAccent,
            fontSize: 20
        ),
      ),
    );
  }
}

执行结果 :

三、相关资源

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参考资料 :

• Flutter 官网 : https://flutter.dev/
• Flutter 插件下载地址 : https://pub.dev/packages
• Flutter 开发文档 : https://flutter.cn/docs ( 强烈推荐 )
• 官方 GitHub 地址 : https://github.com/flutter
• Flutter 中文社区 : https://flutter.cn/
• Flutter 实用教程 : https://flutter.cn/docs/cookbook
• Flutter CodeLab : https://codelabs.flutter-io.cn/
• Dart 中文文档 : https://dart.cn/
• Dart 开发者官网 : https://api.dart.dev/
• Flutter 中文网 : https://flutterchina.club/ , http://flutter.axuer.com/docs/
• Flutter 相关问题 : https://flutterchina.club/faq/ ( 入门阶段推荐看一遍 )
• GitHub 上的 Flutter 开源示例 : https://download.csdn.net/download/han1202012/15989510
• Flutter 实战电子书 : https://book.flutterchina.club/chapter1/
• Dart 语言练习网站 : https://dartpad.dartlang.org/

重要的专题 :

• Flutter 动画参考文档 : https://flutterchina.club/animations/

博客源码下载 :

• GitHub 地址 : https://github.com/han1202012/flutter_listview ( 随博客进度一直更新 , 有可能没有本博客的源码 )

• 博客源码快照 : https://download.csdn.net/download/han1202012/21601609 ( 本篇博客的源码快照 , 可以找到本博客的源码 )