Flutter基础篇07--状态管理方案：Provide

Provide是Google官方推出的状态管理模式。官方地址为：https://github.com/google/flutter-provide

下面通过使用Provide来实现如下效果

1、Provide引入项目

provide: ^1.0.2

2、创建Provide

通过notifyListeners可以通知监听者刷新。

import 'package:flutter/material.dart';

class Counter with ChangeNotifier {
  int value =0 ;
  //数字+1
  increment(){
    value++;
    notifyListeners();
  }
}

3、页面编写

import 'package:flutter/material.dart';

import 'package:provide/provide.dart';
import '../provide/counter.dart';

class CartPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          children: <Widget>[
            MyNumber(),
            MyButton()
          ],
        )
      ),
    );
  }
}

class MyNumber extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      margin: EdgeInsets.only(top: 200),
      //获取数字值
      child: Provide<Counter>(
          builder: (context, child, counter) {
            return Text('${counter.value}', style: TextStyle(fontSize: 30),);
          }
      ),
    );
  }
}

class MyButton extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      child: RaisedButton(
        onPressed: (){
          //修改数字值
          Provide.value<Counter>(context).increment();
        },
        child: Text('递增'),
      ),
    );
  }
}

4、修改main.dart

新添加
import 'package:provide/provide.dart';
import './provide/counter.dart';

void main(){
  var counter = Counter();
  var provides = Providers();
  provides..provide(Provider<Counter>.value(counter));
  runApp(ProviderNode(child: MyApp(), providers: provides));
}