你想搞得跟它一样？

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

void main() {
  WidgetsFlutterBinding.ensureInitialized();

  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'My Title',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        scaffoldBackgroundColor: Colors.black,
        dialogBackgroundColor: Colors.black,
        primarySwatch: Colors.grey,
        cardColor: Colors.white70,
        accentColor: Colors.black,
      ),
      home: Scaffold(
        body: Container(
          decoration: BoxDecoration(
            image: DecorationImage(
              image: AssetImage("assets/bg.png"),
              fit: BoxFit.cover,
            ),
          ),
          child: null /* add child content here */,
        ),
      ),
    );
  }
}

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试试这个

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'My Title',
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Container(
          decoration: BoxDecoration(
            image: DecorationImage(
              image: AssetImage("assets/bg.png"),
              fit: BoxFit.fill,
            ),
          ),
          child: null /* add child content here */,
        ),
      ),
    );
  }
}
        ),
      ),
    );
  }
}

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并且不要忘记在pubspec.yaml文件中添加一个assetfile