Flutter分组无限滚动列表插件grouped_infinite_list的使用

grouped_infinite_list 是一个用于在Flutter中实现双向无限滚动列表的插件。它基于 CustomScrollView 和两个 SliverList 实现，允许你创建具有分组功能的无限滚动列表。

安装

步骤

1. 确保已安装Flutter SDK：请参考 Flutter官方文档 进行安装。

2. 添加依赖

   在你的 pubspec.yaml 文件中添加 grouped_infinite_list 依赖：

   dependencies:
     grouped_infinite_list: ^latest_version
   

3. 安装包

   运行以下命令来安装新添加的依赖：

   flutter packages get
   

参数说明

以下是 GroupedInfiniteList 的一些主要参数：

更多详细参数信息请参见插件文档。

示例代码

下面是一个完整的示例，展示如何使用 grouped_infinite_list 创建一个带有聊天气泡的双向无限滚动列表。

import 'package:flutter/material.dart';
import 'package:grouped_infinite_list/grouped_infinite_list.dart';
import 'package:intl/intl.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final dateFormat = DateFormat('dd MMM yyyy HH:mm:ss');
  final List<ChatPost> positiveItems = [];
  final List<ChatPost> negativeItems = [];
  final ScrollController _scrollController = ScrollController();
  bool _isPositiveLoading = false;
  bool _isNegativeLoading = false;

  @override
  void initState() {
    _addPositiveItem(10);
    _addNegativeItem(10);
    _scrollController.addListener(_scrollListener);
    super.initState();
  }

  void _scrollListener() {
    var thresholdPixels = 120;
    var nextPageTrigger =
        _scrollController.position.maxScrollExtent - thresholdPixels;
    var previousPageTrigger =
        _scrollController.position.minScrollExtent + thresholdPixels;

    if (_scrollController.position.pixels > nextPageTrigger) {
      _addPositiveItemAsync(10);
    }

    if (_scrollController.position.pixels < previousPageTrigger) {
      _addNegativeItemAsync(10);
    }
  }

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

  @override
  Widget build(BuildContext context) {
    final offset = MediaQuery.of(context).viewPadding.top + kToolbarHeight;

    return Scaffold(
      extendBodyBehindAppBar: true,
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.primary.withOpacity(0.85),
        title: const Text('Grouped Infinite List'),
      ),
      body: GroupedInfiniteList(
        controller: _scrollController,
        positiveItems: positiveItems,
        negativeItems: negativeItems,
        useStickyGroupSeparators: true,
        groupBy: (item) => item.dateOnly,
        stickyHeaderPositionOffset: offset,
        groupSeparatorPadding: const EdgeInsets.symmetric(vertical: 8.0),
        groupSeparatorBuilder: (item) {
          return Container(
            alignment: Alignment.center,
            child: Container(
              padding: const EdgeInsets.symmetric(
                vertical: 4.0,
                horizontal: 12.0,
              ),
              decoration: BoxDecoration(
                color: Colors.grey.shade100,
                borderRadius: BorderRadius.circular(12),
              ),
              child: Text(
                DateFormat('dd MMMM yyyy').format(item.date),
                style: TextStyle(
                  color: Colors.grey.shade600,
                  fontWeight: FontWeight.w600,
                ),
              ),
            ),
          );
        },
        itemComparator: (item1, item2) => item1.date.compareTo(item2.date),
        suffix: _isPositiveLoading
            ? const Center(child: CircularProgressIndicator())
            : null,
        negativeSuffix: _isNegativeLoading
            ? const Center(child: CircularProgressIndicator())
            : null,
        itemBuilder: (context, item) {
          return ChatBubble(
            message: item.message,
            isMe: item.isMe,
          );
        },
      ),
    );
  }

  Future<void> _addPositiveItemAsync(int count) async {
    if (_isPositiveLoading) return;
    setState(() => _isPositiveLoading = true);
    await Future.delayed(const Duration(milliseconds: 1500));
    _addPositiveItem(count);
    setState(() => _isPositiveLoading = false);
  }

  Future<void> _addNegativeItemAsync(int count) async {
    if (_isNegativeLoading) return;
    setState(() => _isNegativeLoading = true);
    await Future.delayed(const Duration(milliseconds: 1500));
    _addNegativeItem(count);
    setState(() => _isNegativeLoading = false);
  }

  void _addPositiveItem(int count) {
    final int startIndex = positiveItems.length;
    final ChatPost? lastItem = positiveItems.isNotEmpty ? positiveItems.last : null;
    final date = lastItem?.date ?? DateTime.now();
    positiveItems.addAll(
      List<ChatPost>.generate(
        count,
        (index) => ChatPost(
          message: 'Message ${startIndex + index} ${dummyMessageList[index % dummyMessageList.length]}',
          date: date.add(Duration(hours: (index + 1) * 2)),
          isMe: index % 2 == 0,
        ),
      ),
    );
  }

  void _addNegativeItem(int count) {
    final int startIndex = negativeItems.length;
    final ChatPost? lastItem = negativeItems.isNotEmpty ? negativeItems.last : null;
    final date = lastItem?.date ?? DateTime.now();

    negativeItems.addAll(
      List<ChatPost>.generate(
        count,
        (index) => ChatPost(
          message: 'Message ${(startIndex + index + 1) * -1} ${dummyMessageList[index % dummyMessageList.length]}',
          date: date.subtract(Duration(hours: (index + 1) * 2)),
          isMe: index % 2 == 1,
        ),
      ),
    );
  }
}

class ChatPost {
  ChatPost({
    required this.message,
    required this.date,
    required this.isMe,
  });

  final String message;
  final DateTime date;
  final bool isMe;

  DateTime get dateOnly => DateTime(date.year, date.month, date.day);
}

class ChatBubble extends StatelessWidget {
  final String message;
  final bool isMe;

  const ChatBubble({super.key, required this.message, required this.isMe});

  @override
  Widget build(BuildContext context) {
    return LayoutBuilder(builder: (context, sizingInformation) {
      final maxWidth = sizingInformation.maxWidth;
      return Column(
        crossAxisAlignment: isMe ? CrossAxisAlignment.end : CrossAxisAlignment.start,
        children: [
          Container(
            constraints: BoxConstraints(maxWidth: maxWidth * 0.8),
            decoration: BoxDecoration(
              color: isMe ? Colors.blue : Colors.grey.shade300,
              borderRadius: BorderRadius.only(
                topLeft: const Radius.circular(12),
                topRight: const Radius.circular(12),
                bottomLeft: isMe ? const Radius.circular(12) : const Radius.circular(0),
                bottomRight: isMe ? const Radius.circular(0) : const Radius.circular(12),
              ),
            ),
            padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 10),
            margin: const EdgeInsets.symmetric(horizontal: 16, vertical: 4),
            child: Text(
              message,
              style: TextStyle(
                color: isMe ? Colors.white : Colors.black,
              ),
            ),
          ),
        ],
      );
    });
  }
}

List<String> dummyMessageList = [
  'Lorem ipsum',
  'Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.',
  'Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.',
  'Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.',
  'Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.',
];

以上示例展示了如何创建一个包含双向无限滚动和分组功能的列表，并且实现了加载动画效果。你可以根据需要进行自定义和扩展。