Flutter实时数据流插件stream_live_data的使用

Flutter 实时数据流插件 stream_live_data 的使用

Getting Started（入门）

要开始使用 stream_live_data 插件，首先需要在项目的 pubspec.yaml 文件中添加依赖项。

dependencies:
    stream_live_data: ^0.0.2

接下来，初始化一个 LiveData 实例。例如：

LiveData<String> liveData = LiveData<String>();

订阅变化

注册到 LiveData 的变化。每当数据发生变化时，会触发回调函数。

LiveDataToken token = liveData.register((event) {
  print("Event Received: $event");
});

更新数据

更新 LiveData 的值。这将触发所有订阅者（即注册的回调函数）。

liveData.add(newValue);

清理资源

当不再需要监听数据变化时，记得取消注册以释放资源。

liveData.unRegister(token);
// 或者
token.cancel();

完整示例 Demo

以下是一个完整的示例代码，展示了如何使用 stream_live_data 插件来管理实时数据流。

import 'dart:async';

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

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

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

  [@override](/user/override)
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  final MutableLiveData<String> liveData = MutableLiveData<String>(initValue: "first value");
  final MutableLiveData<String> filter = MutableLiveData<String>(initValue: "");
  final MutableLiveData<List<String>> list = MutableLiveData<List<String>>(initValue: ["a", "b", "c"]);
  final StreamController<String> controller = StreamController<String>.broadcast();
  late final LiveData<String> fromStream = LiveData.fromStream(stream: controller.stream, initValue: "");
  late final LiveData<String> fromStream2 = fromStream.map((e) => "e+ ${e ?? ""}");
  late final LiveData<List<String>?> filteredList = LiveData.transform<List<String>?, List<String>?, List<String>?>(filter, list,
      (a, b) {
    if (a?.isEmpty ?? true) return b;
    textToUpdate = "List filtered";
    return b?.where((element) => element == a).toList();
  }, onError: (e) {
    setState(() {
      textToUpdate = e.toString();
    });
  });

  LiveDataToken? token;
  LiveDataToken? filterToken;
  String textToUpdate = "";

  [@override](/user/override)
  void initState() {
    super.initState();
    textToUpdate = liveData.value ?? "";
    token = liveData.register((event) {
      setState(() {
        // 调用 setState 更新文本
        textToUpdate = event ?? "";
      });
    });
    filterToken = filteredList.register((event) {
      setState(() {});
    });
    controller.stream.listen((event) {
      setState(() {
        textToUpdate = event.toString();
      });
    });
  }

  [@override](/user/override)
  void dispose() {
    super.dispose();
    token?.cancel();
    filterToken?.cancel();
  }

  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
            appBar: AppBar(
              title: const Text('Live data example app'),
            ),
            body: Column(children: [
              TextField(onChanged: (value) {
                filter.add(value);
              }),
              Text(filteredList.value?.toString() ?? ""),
              TextButton(onPressed: () => liveData.add("new value"), child: const Text("更新实时数据为新值")),
              TextButton(onPressed: () => filter.dispose(), child: const Text("销毁过滤器实时数据")),
              TextButton(onPressed: () => filter.addError("发生错误"), child: const Text("添加错误")),
              TextButton(onPressed: () => controller.add("a ${fromStream.value ?? ""}"), child: const Text("向 StreamController 添加数据")),
              TextButton(onPressed: () => fromStream.dispose(), child: const Text("销毁 fromStream")),
              Text("文本: $textToUpdate"),
              LiveDataBuilder(
                  liveData: liveData,
                  builder: (context, snapshot) {
                    return Text("构建器: ${snapshot.data}");
                  }),
              LiveDataBuilder(
                  liveData: fromStream,
                  builder: (context, snapshot) {
                    return Text("fromStream: ${snapshot.data}");
                  })
            ])));
  }
}