Flutter StreamBuilder实现局部刷新实例详解

 const StreamBuilder({
     Key? key,
     this.initialData,
     Stream<T>? stream,
     required this.builder,
   }) : assert(builder != null),
        super(key: key, stream: stream);

 typedef AsyncWidgetBuilder<T> = Widget Function(BuildContext context, AsyncSnapshot<T> snapshot);
 final AsyncWidgetBuilder<T> builder;

 int a = 0;
 // 1、声明一个StreamController类型的控制器，命名为streamController；
 final StreamController<int> streamController = StreamController();
 @override
 Widget build(BuildContext context) {
   return Scaffold(
     appBar: AppBar(),
     body: Center(
       child: Column(
         mainAxisAlignment: MainAxisAlignment.center,
         children: [
           // 2、将需要局部刷新数据的组件嵌套在StreamBuilder组件内，并接收信息；
           StreamBuilder<int>(
             stream: streamController.stream,
             initialData: a,
             builder: (BuildContext context, AsyncSnapshot<int> snapshot) {
               return Text('a : $a');
             },
           ),
           ElevatedButton(
             onPressed: () {
               a++;
               setState(() {});
             },
             child: Text('setState'),
           ),
           ElevatedButton(
             onPressed: () {
               a++;
               // 3、往`StreamBuilder`里添加数据，并通知`StreamBuilder`重新构建；
               streamController.add(a);
             },
             child: Text('streamBuilder'),
           ),
         ],
       ),
     ),
   );
 }
 @override
 void dispose() {
   // TODO: implement dispose
   super.dispose();
   // 4、关流，避免内存泄漏
   streamController.close();
 }