Flutter StatefulBuilder实现局部刷新实例详解

 int a = 0;
 int b = 0;
 @override
 Widget build(BuildContext context) {
   return Scaffold(
     body: Center(
       child: Column(
         mainAxisAlignment: MainAxisAlignment.center,
         children: [
           // 点击按钮，数据‘a'加1，并刷新页面
           ElevatedButton(
             onPressed: () {
               a++;
               setState(() {});
             },
             child: Text('a : $a'),
           ),
           // 点击按钮，数据‘b'加1，并刷新页面
           ElevatedButton(
             onPressed: () {
               b++;
               setState(() {});
             },
             child: Text('b : $b'),
           ),
         ],
       ),
     ),
   );
 }

 const StatefulBuilder({
     Key? key,
     required this.builder,
   }) : assert(builder != null),
 super(key: key);  

 typedef StatefulWidgetBuilder = Widget Function(BuildContext context, StateSetter setState);
 final StatefulWidgetBuilder builder;

 int a = 0;
 int b = 0;
 // 1、定义一个叫做“aState”的StateSetter类型方法；
 StateSetter? aState;
 @override
 Widget build(BuildContext context) {
   return Scaffold(
     body: Center(
       child: Column(
         mainAxisAlignment: MainAxisAlignment.center,
         children: <Widget>[
           // 2、将第一个“ElevatedButton”组件嵌套在“StatefulBuilder”组件内；
           StatefulBuilder(
             builder: (BuildContext context, StateSetter setState) {
               aState = setState;
               return ElevatedButton(
                 onPressed: () {
                   a++;
                   // 3、调用“aState”方法对“StatefulBuilder”内部进行刷新；
                   aState(() {});
                 },
                 child: Text('a : $a'),
               );
             },
           ),
           ElevatedButton(
             onPressed: () {
               b++;
               setState(() {});
             },
             child: Text('b : $b'),
           ),
         ],
       ),
     ),
   );
 }