Flutter / Dart -我有一个简单的应用程序，但我是编程新手，所以很挣扎。
目前，设置是将所有TextInput框都放在一个Column中。我想将其更改为放在一个Row中。我以为这很简单，只需将第44行的Word Column替换为Row即可。但它不起作用，当我尝试运行它时，“errors_patch.dart”页面打开（我以前从未见过），在第51行有一个突出显示的错误“int assertionStart，int assertionEnd，Object”消息）;“.
如何简单地从“列”更改为“行”？
如何真实的显示结果，而不需要单击“减法”按钮来获得结果？
提前感谢。

import 'package:flutter/material.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    const appTitle = 'Help with a meal....';
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: appTitle,
      home: Scaffold(
        appBar: AppBar(
          title: const Text(appTitle),
          backgroundColor: Colors.grey,
          foregroundColor: Colors.black,
        ),
        body: const AddTwoNumbers(),
      ),
    );
  }
}

class AddTwoNumbers extends StatefulWidget {
  const AddTwoNumbers({super.key});

  @override
  // ignore: library_private_types_in_public_api
  _AddTwoNumbersState createState() => _AddTwoNumbersState();
}

class _AddTwoNumbersState extends State<AddTwoNumbers> {
  TextEditingController num1controller = TextEditingController();
  TextEditingController num2controller = TextEditingController();
  TextEditingController num3controller = TextEditingController();
  TextEditingController num4controller = TextEditingController();
  String result = "0";
  @override
  Widget build(BuildContext context) {
    return Container(
      padding: const EdgeInsets.all(10.0),
      child: Column(
        children: <Widget>[
          TextField(
            keyboardType: const TextInputType.numberWithOptions(decimal: true),
            controller: num1controller,
            decoration: const InputDecoration(
              border: OutlineInputBorder(),
              labelText: 'Target Level',
              hintText: 'Enter First Number',
            ),
          ),
          const SizedBox(
            height: 8,
          ),
          TextField(
            keyboardType: const TextInputType.numberWithOptions(decimal: true),
            controller: num2controller,
            decoration: const InputDecoration(
              border: OutlineInputBorder(),
              labelText: 'Current Level',
              hintText: 'Enter Second Number',
            ),
          ),
          const SizedBox(
            height: 8,
          ),
          TextField(
            keyboardType: const TextInputType.numberWithOptions(decimal: true),
            controller: num3controller,
            decoration: const InputDecoration(
              border: OutlineInputBorder(),
              labelText: 'Current Meal carbs',
              hintText: 'Enter Third Number',
            ),
          ),
          const SizedBox(
            height: 8,
          ),
          TextField(
            keyboardType: const TextInputType.numberWithOptions(decimal: true),
            controller: num4controller,
            decoration: const InputDecoration(
              border: OutlineInputBorder(),
              labelText: 'Current Meal carbs 2',
              hintText: 'Enter Fourth Number',
            ),
          ),
          const SizedBox(
            height: 8,
          ),
          Wrap(children: [
            ElevatedButton(
              style: ElevatedButton.styleFrom(
                  foregroundColor: Colors.white,
                  backgroundColor: Colors.purple),
              child: const Text("Subtraction"),
              onPressed: () {
                setState(() {
                  double sum = double.parse(num1controller.text) -
                      double.parse(num2controller.text);
                  result = sum.toStringAsFixed(1);
                });
              },
            ),
            const SizedBox(
              height: 20,
              width: 20,
            ),
          ]),
          Text('Difference between Target Level and Current Level: $result'),
        ],
      ),
    );
  }
}

import 'package:flutter/material.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    const appTitle = 'Help with a meal....';
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: appTitle,
      home: Scaffold(
        appBar: AppBar(
          title: const Text(appTitle),
          backgroundColor: Colors.grey,
          foregroundColor: Colors.black,
        ),
        body: const AddTwoNumbers(),
      ),
    );
  }
}

class AddTwoNumbers extends StatefulWidget {
  const AddTwoNumbers({super.key});

  @override
  // ignore: library_private_types_in_public_api
  _AddTwoNumbersState createState() => _AddTwoNumbersState();
}

class _AddTwoNumbersState extends State<AddTwoNumbers> {
  TextEditingController num1controller = TextEditingController();
  TextEditingController num2controller = TextEditingController();
  TextEditingController num3controller = TextEditingController();
  TextEditingController num4controller = TextEditingController();
  String result = "0";

  _calculate() {
    if (num1controller.text.isNotEmpty && num2controller.text.isNotEmpty) {
      setState(() {
        double sum = double.parse(num1controller.text) -
            double.parse(num2controller.text);
        result = sum.toStringAsFixed(1);
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(
        body: Container(
          padding: const EdgeInsets.all(10.0),
          child: Column(
            children: [
              Row(
                children: <Widget>[
                  Expanded(
                    child: TextField(
                      onChanged: (value) => _calculate(),
                      keyboardType:
                          const TextInputType.numberWithOptions(decimal: true),
                      controller: num1controller,
                      decoration: const InputDecoration(
                        border: OutlineInputBorder(),
                        labelText: 'Target Level',
                        hintText: 'Enter First Number',
                      ),
                    ),
                  ),
                  const SizedBox(
                    width: 8,
                  ),
                  Expanded(
                    child: TextField(
                      onChanged: (value) => _calculate(),
                      keyboardType:
                          const TextInputType.numberWithOptions(decimal: true),
                      controller: num2controller,
                      decoration: const InputDecoration(
                        border: OutlineInputBorder(),
                        labelText: 'Current Level',
                        hintText: 'Enter Second Number',
                      ),
                    ),
                  ),
                  const SizedBox(
                    width: 8,
                  ),
                  Expanded(
                    child: TextField(
                      onChanged: (value) => _calculate(),
                      keyboardType:
                          const TextInputType.numberWithOptions(decimal: true),
                      controller: num3controller,
                      decoration: const InputDecoration(
                        border: OutlineInputBorder(),
                        labelText: 'Current Meal carbs',
                        hintText: 'Enter Third Number',
                      ),
                    ),
                  ),
                  const SizedBox(
                    width: 8,
                  ),
                  Expanded(
                    child: TextField(
                      onChanged: (value) => _calculate(),
                      keyboardType:
                          const TextInputType.numberWithOptions(decimal: true),
                      controller: num4controller,
                      decoration: const InputDecoration(
                        border: OutlineInputBorder(),
                        labelText: 'Current Meal carbs 2',
                        hintText: 'Enter Fourth Number',
                      ),
                    ),
                  ),
                  const SizedBox(
                    width: 8,
                  ),
                ],
              ),
              Text(
                  'Difference between Target Level and Current Level: $result'),
            ],
          ),
        ),
      ),
    );
  }
}