Flutter网络图片缓存与加载插件rxcache_network_image的使用

rxcache_network_image 是一个用于Flutter应用中高效加载和缓存网络图片的插件。它支持磁盘缓存和内存缓存，并且允许预加载图片以提高用户体验。

主要特性

• 磁盘缓存图片
• 内存缓存图片
• 使用 RxCacheManager 预加载图片

开始使用

首先，在你的 pubspec.yaml 文件中添加依赖：

dependencies:
  rxcache_network_image: 1.0.7

然后运行 flutter pub get 来安装这个包。

基本用法

显示缓存的网络图片

你可以使用 RxImage.cacheNetwork 小部件来显示缓存的网络图片：

RxImage.cacheNetwork(
  url: 'https://example.com/image.png',
);

设置内存缓存大小

你可以通过 setMemoryCache 方法设置内存缓存的大小：

cacheManager.setMemoryCache(size); // size in bytes

下载图片

使用 download 方法下载并缓存图片：

cacheManager.download(url: 'https://example.com/image.png');

获取缓存文件

使用 getFile 方法获取缓存的文件：

final file = await cacheManager.getFile('https://example.com/image.png');

创建自定义 CacheManager

你可以创建自己的 CacheManager 类，以便根据需要进行定制：

class CustomCacheManager extends BaseRxCacheManager {
  static CustomCacheManager? _instance;

  CustomCacheManager._({String folder = "rx_image_cache"}) : super(folder: folder);

  factory CustomCacheManager({String folder = "rx_image_cache"}) {
    _instance ??= CustomCacheManager._(folder: folder);
    return _instance!;
  }
}

示例代码

以下是一个完整的示例，展示了如何在Flutter应用中使用 rxcache_network_image 插件：

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

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

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

  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

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

  final String title;

  [@override](/user/override)
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final cacheManager = RxCacheManager();
  final showList = ValueNotifier(true);
  bool allowLoad = true;
  final items = [
    "https://images.pexels.com/photos/18280488/pexels-photo-18280488.jpeg?auto=compress&cs=tinysrgb&w=1200&lazy=load",
    "https://images.pexels.com/photos/19564349/pexels-photo-19564349.jpeg?auto=compress&cs=tinysrgb&w=1260&h=750&dpr=2",
  ];

  [@override](/user/override)
  void didChangeDependencies() async {
    for (var element in urls) {
      cacheManager.download(url: element);
    }
    super.didChangeDependencies();
  }

  [@override](/user/override)
  void dispose() {
    showList.dispose();
    super.dispose();
  }

  [@override](/user/override)
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: Column(
        children: [
          const SizedBox(height: 30),
          SizedBox(
            height: 600,
            width: double.infinity,
            child: ValueListenableBuilder(
              valueListenable: showList,
              builder: (context, value, child) {
                return value
                    ? NotificationListener<ScrollNotification>(
                        onNotification: (details) {
                          if (details.metrics.pixels == details.metrics.maxScrollExtent) {
                            if (allowLoad) {
                              loadMore();
                            }
                          }
                          return true;
                        },
                        child: ListView.builder(
                          itemCount: items.length,
                          itemBuilder: (context, index) {
                            return RxImage.cacheNetwork(
                              url: items[index],
                              width: double.infinity,
                              fit: BoxFit.cover,
                              height: 300,
                            );
                          },
                        ),
                      )
                    : const SizedBox.shrink();
              },
            ),
          ),
        ],
      ),
      floatingActionButton: FloatingActionButton.small(onPressed: () {
        showList.value = !showList.value;
      }),
    );
  }

  void loadMore() async {
    allowLoad = false;
    await Future.delayed(const Duration(milliseconds: 750), () {
      debugPrint("wait preload");
    });

    for (final url in urls) {
      cacheManager.download(url: url);
    }

    setState(() {
      items.addAll(urls);
    });
  }
}

const urls = [
  "https://images.pexels.com/photos/19560944/pexels-photo-19560944.jpeg?auto=compress&cs=tinysrgb&w=1260&h=750&dpr=2",
  "https://images.pexels.com/photos/17889085/pexels-photo-17889085.jpeg?auto=compress&cs=tinysrgb&w=1260&h=750&dpr=2",
  "https://images.pexels.com/photos/19542480/pexels-photo-19542480.jpeg?auto=compress&cs=tinysrgb&w=1260&h=750&dpr=2",
  // 更多URL...
];