做网站怎样投放广告网络营销有哪些手段

1.说明

无意间发现了一个好用的库rxdart，它为 Dart 的 Stream 添加了额外的功能。

2.功能

（1）合并多个流Stream

借助Rx.combineLatest2()合并两个流stream1和stream2。
注意：如果dart文件中同时使用了getx，需要隐藏掉Rx，否则会冲突。

import 'dart:async';import 'package:flutter/material.dart';
import 'package:rxdart/rxdart.dart';
// import 'package:get/get.dart' hide Rx;// Library: rxdart , v0.28.0
// 为 Dart 的 Stream 添加了额外的功能
// 合并多个流 CombineLatestStream// Publisher: fluttercommunity.devclass RxdartDemo extends StatefulWidget {const RxdartDemo({super.key});@overrideState<RxdartDemo> createState() => _RxdartDemoState();
}class _RxdartDemoState extends State<RxdartDemo> {//（热重载报错） Unhandled Exception: Bad state: Stream has already been listened to.// 解决：更改为广播流（broadcast）。StreamController<String> streamController1 = StreamController<String>.broadcast();late Stream<String> stream1;StreamController<int> streamController2 = StreamController<int>.broadcast();late Stream<int> stream2;StreamController<List<int>> streamController3 = StreamController<List<int>>.broadcast();late Stream<List<int>> stream3;@overridevoid initState() {super.initState();stream1 = streamController1.stream;streamController1.add("A");stream2 = streamController2.stream;streamController2.add(1);stream3 = streamController3.stream;streamController3.add([1, 2]);}@overridevoid dispose() {streamController1.close();streamController2.close();streamController3.close();super.dispose();}// Rx.combineLatest2 将两个Stream流合并Stream<String> get streamCombined =>Rx.combineLatest2(stream1, stream2, (a, b) => '$a - $b');@overrideWidget build(BuildContext context) {return Scaffold(body: Center(child: Column(mainAxisAlignment: MainAxisAlignment.center,children: [const Text("单个流Stream",style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),),const SizedBox(height: 12,),StreamBuilder<List<int>>(stream: stream3,builder: (context, snapshot) {return Text("${snapshot.data}",style: const TextStyle(fontSize: 16),);}),const SizedBox(height: 12,),const Text("合并多个流Stream",style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),),const SizedBox(height: 12,),StreamBuilder<String>(stream: streamCombined,builder: (context, snapshot) {return Text(snapshot.data ?? 'empty',style: const TextStyle(fontSize: 16),);}),TextButton(onPressed: () {streamController1.add("b");streamController2.add(2);streamController3.add([3, 4]);},child: const Text('Change',style: TextStyle(fontSize: 16, color: Colors.blue),))],),),);}
}