flutter3默认空白页

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: '程序名称',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: '顶部标题'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: SafeArea(
        child: Container(),
      ),
    );
  }
}

　　删除了

int _counter = 0;  
  
void _incrementCounter() {  
  setState(() {  
    _counter++;  
  });  
}

floatingActionButton: FloatingActionButton(  
  onPressed: _incrementCounter,  
  tooltip: 'Increment',  
  child: const Icon(Icons.add),  
),

　　删除了

body: Center(  
  child: Column(  
    mainAxisAlignment: MainAxisAlignment.center,  
    children: <Widget>[  
      const Text(  
        'You have pushed the button this many times:',  
      ),  
      Text(  
        '$_counter',  
        style: Theme.of(context).textTheme.headlineMedium,  
      ),  
    ],  
  ),  
),

　　替换为

body: SafeArea(
  child: Container(),
),

　记录最终例子

import 'package:flutter/material.dart';

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

class GoWaterMyApp extends StatelessWidget {
  const GoWaterMyApp({super.key});
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: '程序名称',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.lightBlue),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: '顶部标题'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: SafeArea(
        child: Container(),
      ),
    );
  }
}