“IconData”类型不是“Widget”类型的子类型

Question

浏览“向您的 Flutter 应用程序添加交互性”教程时，我一直运行到此错误消息：

类型 'IconData' 不是类型 'Widget' 的子类型

由于我缺乏经验，我不确定补救措施是什么。作为一个教程，我找到了答案代码并将其复制粘贴到 Visual Studio 中，只是为了看看它的外观。我收到了同样的错误。我通过堆栈溢出和 github 做了一些查看。我找到的示例在故障代码中专门调用了 IconData。在教程代码中，它只调用了一次 IconData，它是一个完全不同的小部件。

 import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    Widget titleSection = Container(
      padding: const EdgeInsets.all(32),
      child: Row(
        children: [
          Expanded(
            /*1*/
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                /*2*/
                Container(
                  padding: const EdgeInsets.only(bottom: 8),
                  child: Text(
                    'Oeschinen Lake Campground',
                    style: TextStyle(
                      fontWeight: FontWeight.bold,
                    ),
                  ),
                ),
                Text(
                  'Kandersteg, Switzerland',
                  style: TextStyle(
                    color: Colors.grey[500],
                  ),
                ),
              ],
            ),
          ),
          FavoriteWidget(),
        ],
      ),
    );

    Color color = Theme.of(context).primaryColor;

    Widget buttonSection = Container(
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        children: [
          _buildButtonColumn(color, Icons.call, 'CALL'),
          _buildButtonColumn(color, Icons.near_me, 'ROUTE'),
          _buildButtonColumn(color, Icons.share, 'SHARE'),
        ],
      ),
    );

    Widget textSection = Container(
      padding: const EdgeInsets.all(32),
      child: Text(
        'Lake Oeschinen lies at the foot of the Blüemlisalp in the Bernese '
            'Alps. Situated 1,578 meters above sea level, it is one of the '
            'larger Alpine Lakes. A gondola ride from Kandersteg, followed by a '
            'half-hour walk through pastures and pine forest, leads you to the '
            'lake, which warms to 20 degrees Celsius in the summer. Activities '
            'enjoyed here include rowing, and riding the summer toboggan run.',
        softWrap: true,
      ),
    );

    return MaterialApp(
      title: 'Flutter layout demo',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Flutter layout demo'),
        ),
        body: ListView(
          children: [
            Image.asset(
              'images/lake.jpg',
              width: 600,
              height: 240,
              fit: BoxFit.cover,
            ),
            titleSection,
            buttonSection,
            textSection,
          ],
        ),
      ),
    );
  }

  Column _buildButtonColumn(Color color, IconData icon, String label) {
    return Column(
      mainAxisSize: MainAxisSize.min,
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        Icon(icon, color: color),
        Container(
          margin: const EdgeInsets.only(top: 8),
          child: Text(
            label,
            style: TextStyle(
              fontSize: 12,
              fontWeight: FontWeight.w400,
              color: color,
            ),
          ),
        ),
      ],
    );
  }
}

// #docregion FavoriteWidget
class FavoriteWidget extends StatefulWidget {
  @override
  _FavoriteWidgetState createState() => _FavoriteWidgetState();
}
// #enddocregion FavoriteWidget

// #docregion _FavoriteWidgetState, _FavoriteWidgetState-fields, _FavoriteWidgetState-build
class _FavoriteWidgetState extends State<FavoriteWidget> {
  // #enddocregion _FavoriteWidgetState-build
  bool _isFavorited = true;
  int _favoriteCount = 41;
  // #enddocregion _FavoriteWidgetState-fields

  // #docregion _toggleFavorite
  void _toggleFavorite() {
    setState(() {
      if (_isFavorited) {
        _favoriteCount -= 1;
        _isFavorited = false;
      } else {
        _favoriteCount += 1;
        _isFavorited = true;
      }
    });
  }
  // #enddocregion _toggleFavorite

  // #docregion _FavoriteWidgetState-build
  @override
  Widget build(BuildContext context) {
    return Row(
      mainAxisSize: MainAxisSize.min,
      children: [
        Container(
          padding: EdgeInsets.all(0),
          child: IconButton(
            padding: EdgeInsets.all(0),
            alignment: Alignment.centerRight,
            icon: (_isFavorited ? Icon(Icons.star) : Icon(Icons.star_border)),
            color: Colors.red[500],
            onPressed: _toggleFavorite,
          ),
        ),
        SizedBox(
          width: 18,
          child: Container(
            child: Text('$_favoriteCount'),
          ),
        ),
      ],
    );
  }
  // #docregion _FavoriteWidgetState-fields
}

该错误还专门引用了第 34 行：第 11 行，即 FavoriteWidget() 行。

感谢您的宝贵时间

Answer 1

您发布的代码对我来说很好。

请务必添加正确的图片资源 (images/lake.jpg)，例如：

请务必在 pubspec.yaml 中设置 uses-material-design: true 以使图标包含在应用程序中。

同时尝试更新flutter并运行flutter doctor看看是否还有其他问题