Question

我是Flutter的初学者。我收到错误消息：类型'IconData'不是'颜色'类型的子类型。我无法在网络上的任何地方找到它。我该如何解决？我正在开发一个简单的应用程序，有2条路线。我正在使用以下GitHub链接中的代码： https://github.com/flutter/udacity-course/tree/master/course/04_navigation/solution_04_navigation

cartegory.dart文件使用IconData。

我有5个.dart文件，如下所示：

main.dart：

import 'package:flutter/material.dart';

// You can use a relative import, i.e. `import 'category.dart';` or
// a package import, as shown below.
// More details at http://dart-lang.github.io/linter/lints/avoid_relative_lib_imports.html
import 'package:testapp/category.dart';
import 'package:testapp/category_route.dart';

// TODO: Pass this information into your custom [Category] widget
const _categoryName = 'Cake';
const _categoryIcon = Icons.cake;
const _categoryColor = Colors.green;

/// The function that is called when main.dart is run.
void main() {
  runApp(UnitConverterApp());
}

/// This widget is the root of our application.
/// Currently, we just show one widget in our app.
class UnitConverterApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      // title: 'Unit Converter',
      home: CategoryRoute(),
    );
  }
}

category_route.dart：

import 'package:flutter/material.dart';

import 'package:testapp/category.dart';
import 'package:testapp/unit.dart';

final _backgroundColor = Colors.green[100];

/// Category Route (screen).
///
/// This is the 'home' screen of the Unit Converter. It shows a header and
/// a list of [Categories].
///
/// While it is named CategoryRoute, a more apt name would be CategoryScreen,
/// because it is responsible for the UI at the route's destination.
class CategoryRoute extends StatelessWidget {
  const CategoryRoute();

  static const _categoryNames = <String>[
    'Length',
    'Area',
    'Volume',
    'Mass',
    'Time',
    'Digital Storage',
    'Energy',
    'Currency',
  ];

  static const _baseColors = <Color>[
    Colors.teal,
    Colors.orange,
    Colors.pinkAccent,
    Colors.blueAccent,
    Colors.yellow,
    Colors.greenAccent,
    Colors.purpleAccent,
    Colors.red,
  ];

  /// Makes the correct number of rows for the list view.
  ///
  /// For portrait, we use a [ListView].
  Widget _buildCategoryWidgets(List<Widget> categories) {
    return ListView.builder(
      itemBuilder: (BuildContext context, int index) => categories[index],
      itemCount: categories.length,
    );
  }

  /// Returns a list of mock [Unit]s.
  List<Unit> _retrieveUnitList(String categoryName) {
    return List.generate(10, (int i) {
      i += 1;
      return Unit(
        name: '$categoryName Unit $i',
        conversion: i.toDouble(),
      );
    });
  }

  @override
  Widget build(BuildContext context) {
    final categories = <Category>[];

    for (var i = 0; i < _categoryNames.length; i++) {
      categories.add(Category(
        name: _categoryNames[i],
        color: _baseColors[i],
        iconLocation: Icons.cake,
        units: _retrieveUnitList(_categoryNames[i]),
      ));
    }

    final listView = Container(
      color: _backgroundColor,
      padding: EdgeInsets.symmetric(horizontal: 8.0),
      child: _buildCategoryWidgets(categories),
    );

    final appBar = AppBar(
      elevation: 0.0,
      title: Text(
        'Unit Converter',
        style: TextStyle(
          color: Colors.black,
          fontSize: 30.0,
        ),
      ),
      centerTitle: true,
      backgroundColor: _backgroundColor,
    );

    return Scaffold(
      appBar: appBar,
      body: listView,
    );
  }
}

converter_route.dart：

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

import 'package:testapp/unit.dart';

/// Converter screen where users can input amounts to convert.
///
/// Currently, it just displays a list of mock units.
///
/// While it is named ConverterRoute, a more apt name would be ConverterScreen,
/// because it is responsible for the UI at the route's destination.
class ConverterRoute extends StatelessWidget {
  /// Units for this [Category].
  final List<Unit> units;

  /// This [ConverterRoute] requires the color and units to not be null.
  // TODO: Pass in the [Category]'s color
  const ConverterRoute({
    @required this.units,
  }) : assert(units != null);

  @override
  Widget build(BuildContext context) {
    // Here is just a placeholder for a list of mock units
    final unitWidgets = units.map((Unit unit) {
      // TODO: Set the color for this Container
      return Container(
        margin: EdgeInsets.all(8.0),
        padding: EdgeInsets.all(16.0),
        child: Column(
          children: <Widget>[
            Text(
              unit.name,
              style: Theme.of(context).textTheme.headline1,
            ),
            Text(
              'Conversion: ${unit.conversion}',
              style: Theme.of(context).textTheme.subtitle1,
            ),
          ],
        ),
      );
    }).toList();

    return ListView(
      children: unitWidgets,
    );
  }
}

category.dart：

import 'package:flutter/material.dart';
// @required is defined in the meta.dart package
import 'package:meta/meta.dart';

import 'package:testapp/converter_route.dart';
import 'package:testapp/unit.dart';

// We use an underscore to indicate that these variables are private.
// See https://www.dartlang.org/guides/language/effective-dart/design#libraries
final _rowHeight = 100.0;
final _borderRadius = BorderRadius.circular(_rowHeight / 2);

/// A custom [Category] widget.
///
/// The widget is composed on an [Icon] and [Text]. Tapping on the widget shows
/// a colored [InkWell] animation.
class Category extends StatelessWidget {
  final String name;
  final ColorSwatch color;
  final IconData iconLocation;
  final List<Unit> units;

  /// Creates a [Category].
  ///
  /// A [Category] saves the name of the Category (e.g. 'Length'), its color for
  /// the UI, and the icon that represents it (e.g. a ruler).
  // While the @required checks for whether a named parameter is passed in,
  // it doesn't check whether the object passed in is null. We check that
  // in the assert statement.
  const Category({
    Key key,
    @required this.name,
    @required this.color,
    @required this.iconLocation,
    @required this.units,
  })  : assert(name != null),
        assert(color != null),
        assert(iconLocation != null),
        assert(units != null),
        super(key: key);

  /// Navigates to the [ConverterRoute].
  void _navigateToConverter(BuildContext context) {
    Navigator.of(context).push(MaterialPageRoute<Null>(
      builder: (BuildContext context) {
        return Scaffold(
          appBar: AppBar(
            elevation: 1.0,
            title: Text(
              name,
              style: Theme.of(context).textTheme.display1,
            ),
            centerTitle: true,
            backgroundColor: color,
          ),
          body: ConverterRoute(
            color: color,
            units: units,
          ),
        );
      },
    ));
  }

  /// Builds a custom widget that shows [Category] information.
  ///
  /// This information includes the icon, name, and color for the [Category].
  @override
  // This `context` parameter describes the location of this widget in the
  // widget tree. It can be used for obtaining Theme data from the nearest
  // Theme ancestor in the tree. Below, we obtain the display1 text theme.
  // See https://docs.flutter.io/flutter/material/Theme-class.html
  Widget build(BuildContext context) {
    return Material(
      color: Colors.transparent,
      child: Container(
        height: _rowHeight,
        child: InkWell(
          borderRadius: _borderRadius,
          highlightColor: color,
          splashColor: color,
          // We can use either the () => function() or the () { function(); }
          // syntax.
          onTap: () => _navigateToConverter(context),
          child: Padding(
            padding: EdgeInsets.all(8.0),
            child: Row(
              crossAxisAlignment: CrossAxisAlignment.stretch,
              // There are two ways to denote a list: `[]` and `List()`.
              // Prefer to use the literal syntax, i.e. `[]`, instead of `List()`.
              // You can add the type argument if you'd like, i.e. <Widget>[].
              // See https://www.dartlang.org/guides/language/effective-dart/usage#do-use-collection-literals-when-possible
              children: [
                Padding(
                  padding: EdgeInsets.all(16.0),
                  child: Icon(
                    iconLocation,
                    size: 60.0,
                  ),
                ),
                Center(
                  child: Text(
                    name,
                    textAlign: TextAlign.center,
                    style: Theme.of(context).textTheme.headline,
                  ),
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

unit.dart：

import 'package:meta/meta.dart';

/// Information about a [Unit].
class Unit {
  final String name;
  final double conversion;

  /// A [Unit] stores its name and conversion factor.
  ///
  /// An example would be 'Meter' and '1.0'.
  const Unit({
    @required this.name,
    @required this.conversion,
  })  : assert(name != null),
        assert(conversion != null);

  /// Creates a [Unit] from a JSON object.
  Unit.fromJson(Map jsonMap)
      : assert(jsonMap['name'] != null),
        assert(jsonMap['conversion'] != null),
        name = jsonMap['name'],
        conversion = jsonMap['conversion'].toDouble();
}

Answer 1

这是您向图标而不是通过IconData添加颜色的方式。

图标（ Icons.widgets，颜色：Colors.blue，）

在Flutter中遇到此错误：“ IconData”类型不是“颜色”类型的子类型

1 个答案: