为什么此代码在运行时显示空白屏幕？

Question

在显示代码之前，我检查了以下内容以避免出现类似的答案：

android:extratNativeLibs="true"
已连接 Jsonfile firebase
routegenerator 和 initialroute 在主文件中检查并且
生成器文件

。我喜欢避免使用 mediaQuery 而使用百分比，这就是我使用 FractionallySizedBox 的原因。这是初始路线的代码：

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

class Start extends StatelessWidget {
  const Start({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
            body: Align(
                alignment: Alignment.center,
                child: Center(
                    child: Column(mainAxisSize: MainAxisSize.min, children: <Widget>[
                  FractionallySizedBox(widthFactor: 0.15, heightFactor: 0.15, child: Image.asset('assets/crown.png')),
                  FractionallySizedBox(
                      widthFactor: 0.40,
                      heightFactor: 0.20,
                      child: TextButton(
                          onPressed: () {
                            Navigator.of(context).pushNamed('/items');
                          },
                          child: Container(
                              decoration: BoxDecoration(color: Colors.purple),
                              child: Row(mainAxisSize: MainAxisSize.min, children: <Widget>[
                                const Text('Start shopping',
                                    style: TextStyle(
                                      color: Colors.white,
                                      fontStyle: FontStyle.italic,
                                      fontSize: 25,
                                    )),
                                Image.asset('assets/crown.png')
                              ]))))
                ])))));
  }
}

Answer 1

用 Expanded

扭曲你的 FractionallySizedBox

              Expanded(
                child: FractionallySizedBox(
                    widthFactor: 0.15,
                    heightFactor: 0.15,
                    child: Image.asset('assets/crown.png')),
              ),
              Expanded(
                child: FractionallySizedBox(
                  widthFactor: 0.40,
                  heightFactor: 0.20,
                  child: TextButton(
                    onPressed: () {
                      Navigator.of(context).pushNamed('/items');
                    },
                    child: Container(
                      decoration: BoxDecoration(color: Colors.purple),
                      child: Row(
                        mainAxisSize: MainAxisSize.min,
                        children: <Widget>[
                          const Text('Start shopping',
                              style: TextStyle(
                                color: Colors.white,
                                fontStyle: FontStyle.italic,
                                fontSize: 25,
                              )),
                          Image.asset('assets/crown.png')
                        ],
                      ),
                    ),
                  ),
                ),
              ),

为什么此代码在 运行 时显示空白屏幕？

Why does this code display a blank screen when running?

android

dart

firebase

flutter

为什么此代码在运行时显示空白屏幕？