Flutter官网demo实现计数器

这个demo中，如果要更新_count++，调用setState就会重新build，这样做比较耗费性能，此时可以使用Getx的响应式状态管理器实现局部刷新

import 'package:flutter/material.dart';class JiShu extends StatefulWidget {const JiShu({Key? key}):super(key:key);@overrideState<JiShu> createState() => _JiShuState();
}class _JiShuState extends State<JiShu> {int _count = 0;@overrideWidget build(BuildContext context) {return Scaffold(appBar: AppBar(title: Text('计数器'),),body: Column(children: [Text('计数器：${_count}'),ElevatedButton(onPressed: (){setState(() {_count++;});}, child: Text('计数器++'))],),);}
}

Getx响应式状态管理器，实现刷新局部数据

Flutter中无状态组件StatelessWidget 是不能触发计数器的，通过Getx响应式状态管理器实现了数字的更新

final _count = 0.obs; // 定义响应式状态
Obx(()=> Text('计数器：${_count.value}')),  // 通过Obx渲染数据
_count.value++; // 改变数据

// main 文件入口必须使用GetMaterialApp包裹以下
return const GetMaterialApp(home: JiShu(),
);import 'package:flutter/material.dart';
import 'package:get/get.dart';class JiShu extends StatelessWidget {const JiShu({Key?key}):super(key: key);@overrideWidget build(BuildContext context) {final _count = 0.obs;final _name = '张三'.obs;return Scaffold(appBar: AppBar(title: Text('计数器'),),body: Column(children: [Obx(()=> Text('计数器：${_count.value}，姓名：${_name.value}')),ElevatedButton(onPressed: (){_count.value++;_name.value = '李四';}, child: Text('计数器++'))],),);}
}

响应式数据定义的方式

final name = ''.obs;
final isLogged = false.obs;
final count = 0.obs;
final balance = 0.0.obs;
final number = 0.obs;
final items = <String>[].obs;
final myMap = <String, int>{}.obs;
自定义类 - 可以是任何类
final user = User().obs;

自定义响应式类

class Animal {String name;int age;Animal(this.name,this.age);
}// 下个页面中使用这个类
import 'animal.dart';
var _animal = Animal('张三', 30).obs;...Obx(()=> Text('计数器：${_animal.value.name}，年龄：${_animal.value.age}')),
ElevatedButton(onPressed: (){_animal.value.name = '李四';_animal.value.age = 40;_animal.value = _animal.value;
}, child: Text('修改自定义类响应式')),