经常碰到非叶子节点的Widget进行setState时会导致其子组件重复的build操作, 像前端框架 React 有生命周期方法 shouldComponentUpdate来确认组件是否进行重新渲染

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: const MyHomePage(title: 'Flutter Demo Home Page'),
      ),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);
  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  int counter = 0;
  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    print("build parent");

    return ListView(children: [

      SonWidget(),

      FloatingActionButton(onPressed: (){
        setState((){
          counter ++;
        });
      })
    ],);
  }
}

class SonWidget extends StatefulWidget{
  const SonWidget({Key? key}) : super(key: key);

  @override
  State<StatefulWidget> createState() => _SonState();
}


class _SonState extends State<SonWidget>{
  @override
  Widget build(BuildContext context) {
    print("build son");
    return Container();
  }
}