相較於一次性的非同步執行緒 FutureBuilder，StreamBuilder 能持續運作並可搭配 StreamController 達到更新畫面資料時，不需要整個重新 build 而只更動使用 StreamBuilder 的區塊。
以下StreamBuilder 範例為使用 dart_ping 套件，建立一個簡易的網址偵測 App。
程式規劃和引用的套件(pubspec.yaml)
main.dart
import 'package:flutter/material.dart';
import 'package:network_toolkit/screens/ping_screen.dart';
void main() {
runApp(
const AppEntryPoint()
);
}
class AppEntryPoint extends StatelessWidget {
const AppEntryPoint({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Network Toolkit',
theme: ThemeData(
useMaterial3: true,
primarySwatch: Colors.green,
),
routes: {
"/ping":(BuildContext context) => const PingScreen(),
},
initialRoute: "/ping",
);
}
}screens/ping_screen.dart
import 'package:flutter/material.dart';
import 'dart:async';
import 'package:dart_ping/dart_ping.dart';
import 'package:network_toolkit/components/ping_result_component.dart';
class PingScreen extends StatefulWidget {
const PingScreen({super.key});
@override
State createState() {
return _PingScreen();
}
}
class _PingScreen extends State<PingScreen> {
bool _userInputTextFieldEnabled = true;
String _urlOrIP = "";
late StreamController _controller;
final ScrollController _scrollController = ScrollController();
List<String> _pingResultList = [];
@override
void initState() {
super.initState();
_controller = StreamController.broadcast(); // Initial
}
@override
Widget build(BuildContext context) {
var textEditController = TextEditingController( text: _urlOrIP );
Widget userInputTextField = SizedBox(
width: 500,
child: TextField(
decoration: const InputDecoration(
border: OutlineInputBorder(),
hintText: 'Input URL or IP',
),
controller: textEditController,
enabled: _userInputTextFieldEnabled,
onSubmitted: (inputvalue){
_urlOrIP = inputvalue;
_pingResultList = [];
setState(() {
_userInputTextFieldEnabled = false;
});
// Begin ping process and listen for output
final ping = Ping(_urlOrIP, count: 5);
ping.stream.listen(
(event) {
_pingResultList.add("${ping.command} : ${event.toString()}");
_controller.sink.add(_pingResultList);
},
onDone: () {
setState(() {
_userInputTextFieldEnabled = true;
});
},
);
},
),
);
return Scaffold(
appBar: AppBar(
title: const Text("Ping"),
),
body: Column(
children: [
userInputTextField,
StreamBuilder(
initialData: _pingResultList,
stream: _controller.stream,
builder: (context, n) {
List<String> results = n.data as List<String>;
return Expanded(
child: ListView(
controller: _scrollController,
children: [
...results.map((pingResult) => PingResultComponent(pingResult)).toList()
]
)
);
}
),
]
),
);
}
@override
void dispose() {
super.dispose();
_controller.close();
}
}components/ping_result_component.dart
import 'package:flutter/material.dart';
// ignore: must_be_immutable
class PingResultComponent extends StatefulWidget {
String pingResult;
PingResultComponent(this.pingResult, {super.key});
@override
State createState() {
return _PingResultComponent();
}
}
class _PingResultComponent extends State<PingResultComponent> {
@override
Widget build(BuildContext context) {
Widget pingResultValueText =
Flexible(
child: Text(
widget.pingResult,
)
);
return Card(
child: ListTile(
title: Row(
children: [
pingResultValueText,
]
),
),
);
}
}
Brassai Kao’s Tech Weave 