今天学习下Flutter中state管理的第三方provide.
其中,provide: ^1.0.2

代码结构如图所示:
provide_demo_代码结构

下面是各文件的源码.

main.dart

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import 'package:flutter/material.dart';
import 'package:provide_demo/tabbar.dart';
import 'package:provide/provide.dart';
import 'package:provide_demo/model/counter.dart';

void main() {
var counter = Counter();
var providers = Providers();

providers
..provide(Provider<Counter>.value(counter));

runApp(ProviderNode(child: MyApp(), providers: providers));
}

class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
// This is the theme of your application.
//
// Try running your application with "flutter run". You'll see the
// application has a blue toolbar. Then, without quitting the app, try
// changing the primarySwatch below to Colors.green and then invoke
// "hot reload" (press "r" in the console where you ran "flutter run",
// or simply save your changes to "hot reload" in a Flutter IDE).
// Notice that the counter didn't reset back to zero; the application
// is not restarted.
primarySwatch: Colors.blue,
),
home: Tabbar(),
);
}
}

tabbar.dart

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import 'package:flutter/material.dart';
import 'One/one.dart';
import 'Two/two.dart';

class Tabbar extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
debugShowCheckedModeBanner: false, home: new MainPageWidget());
}
}

class MainPageWidget extends StatefulWidget {
@override
State<StatefulWidget> createState() {
return new MainPageState();
}
}

class MainPageState extends State<MainPageWidget> {
int _tabIndex = 0;
var tabImages;
var appBarTitles = ['One', 'Two'];
/*
* 存放二个页面,跟fragmentList一样
*/
var _pageList;

/*
* 根据选择获得对应的normal或是press的icon
*/
Image getTabIcon(int curIndex) {
if (curIndex == _tabIndex) {
return tabImages[curIndex][1];
}
return tabImages[curIndex][0];
}
/*
* 获取bottomTab的颜色和文字
*/
Text getTabTitle(int curIndex) {
if (curIndex == _tabIndex) {
return new Text(appBarTitles[curIndex],
style: new TextStyle(fontSize: 14.0, color: const Color(0xff1296db)));
} else {
return new Text(appBarTitles[curIndex],
style: new TextStyle(fontSize: 14.0, color: const Color(0xff515151)));
}
}
/*
* 根据image路径获取图片
*/
Image getTabImage(path) {
return new Image.asset(path, width: 24.0, height: 24.0);
}


void initData() {
/*
* 初始化选中和未选中的icon
*/
tabImages = [
[getTabImage('images/tab/one.png'), getTabImage('images/tab/one_active.png')],
[getTabImage('images/tab/two.png'), getTabImage('images/tab/two_active.png')],
];
/*
* 子界面
*/
_pageList = [
new One(),
new Two(),
];
}

@override
Widget build(BuildContext context) {
//初始化数据
initData();
return Scaffold(
body: _pageList[_tabIndex],
bottomNavigationBar: new BottomNavigationBar(
items: <BottomNavigationBarItem>[
new BottomNavigationBarItem(
icon: getTabIcon(0), title: getTabTitle(0)),
new BottomNavigationBarItem(
icon: getTabIcon(1), title: getTabTitle(1)),
],
type: BottomNavigationBarType.fixed,
//默认选中首页
currentIndex: _tabIndex,
iconSize: 24.0,
//点击事件
onTap: (index) {
setState(() {
_tabIndex = index;
});
},
));
}
}

counter.dart

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import 'package:flutter/material.dart';

class Counter with ChangeNotifier{
int value = 0;

increment(){
value++;
notifyListeners();
}
}

one.dart

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import 'package:flutter/material.dart';
import 'package:provide/provide.dart';
import 'package:provide_demo/model/counter.dart';

class One extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('One')),
body: Padding(
padding: EdgeInsets.only(top: 400.0,left: 200.0),
child: Column(
children: <Widget>[
Provide<Counter>(
builder: (context, child, counter) {
return Text(
'${counter.value}',
);
},
),
IconButton(
icon: Icon(Icons.add),
onPressed: () {
Provide.value<Counter>(context).increment();
},
),
],
),
),
);
}
}

two.dart

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import 'package:flutter/material.dart';
import 'package:provide/provide.dart';
import 'package:provide_demo/model/counter.dart';

class Two extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('Two')),
body: Center(
child: Provide<Counter>(
builder: (context, child, counter) {
return Text(
'${counter.value}',
);
},
),
),
);
}
}

效果图:
provide_demo_result

源码

另外:其他管理库学习

另外:Flutter学习demo