dart笔记19:基于stream流的Flutter
StreamBuilder
组件,可以用来替代
StatefulWidegt
的
setState
方法,做到数据更新,实时渲染页面。
import 'dart:async';
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'StreamBuilder示例',
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key}) : super(key: key);
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _count = 0;
final StreamController<int> _streamController = StreamController();
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('StreamBuilder示例'),
),
body: Container(
child: Center(
child: StreamBuilder(
//流的来源
stream: _streamController.stream,
//将流的内容进行实时渲染
builder: (BuildContext context, AsyncSnapshot snapshot) {
return snapshot.data == null
? Text(
'0',
style: TextStyle(fontSize: 36.0),
)
: Text(
'${snapshot.data}',
style: TextStyle(fontSize: 36.0),
);
},
),
),
),
floatingActionButton: FloatingActionButton(
child: Icon(Icons.add),
onPressed: () {
//往stream流里面加数据
_streamController.sink.add(++_count);
},
),
);
}
@override
void dispose() {
_streamController.close();
super.dispose();
}
}