Flutter StreamBuilder 实现局部刷新 Widget

import 'package:flutter/material.dart';
 
class CustomStreamBuilder extends StatefulWidget {
  final Stream<int> stream;
  final Widget child;
 
  const CustomStreamBuilder({Key key, this.stream, this.child}) : super(key: key);
 
  @override
  _CustomStreamBuilderState createState() => _CustomStreamBuilderState();
}
 
class _CustomStreamBuilderState extends State<CustomStreamBuilder> {
  StreamSubscription<int> _subscription;
  int _count = 0;
 
  @override
  void initState() {
    super.initState();
    _subscription = widget.stream.listen((count) {
      setState(() {
        _count = count;
      });
    });
  }
 
  @override
  void dispose() {
    _subscription?.cancel();
    super.dispose();
  }
 
  @override
  Widget build(BuildContext context) {
    return widget.child;
  }
}

这个代码示例展示了如何创建一个CustomStreamBuilder类，它继承自StatefulWidget。在initState方法中，它订阅了传递给构造函数的流，并在流接收到数据时更新内部的_count状态。如果小部件被销毁，dispose方法将取消订阅，以防止内存泄漏。这个示例展示了如何使用Flutter中的Stream来实现局部刷新Widget的简单方法。