无法创建自定义色板

Question

我正在尝试为应用程序使用自定义颜色主题。

这是main.dart文件

import 'package:flutter/material.dart';

import 'pages/HomePage.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: new ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or press Run > Flutter Hot Reload in IntelliJ). Notice that the
        // counter didn't reset back to zero; the application is not restarted.
        primarySwatch: MaterialColor(0xFF990000, {
          50: Color(0xFF990001),
          300: Color(0xFF990002),
          900: Color(0xFF990003)
        }),
      ),
      home: new HomePage(),
    );
  }
}

我得到以下错误：

flutter: WIDGETS╞═══════════════════════════════════════════════════════════flutter捕获到══╡异常:构建MyApp时抛出以下NoSuchMethodError (脏)：flutter:在null上调用了方法'computeLuminance‘。颤动:接收器:空颤动:尝试调用: computeLuminance()

我做错了什么？

Answer 1

如果你想让它工作，你应该定义所有的值，当我只定义一个或两个值时，我也遇到了同样的错误。

从official documentation我们发现

MaterialColor类定义了一种颜色以及具有该颜色的十种阴影的色样。

例如：

 primarySwatch: MaterialColor(0xFFFFFFFF, {
  50:  Color(0xFFFFFFFF),
  100: Color(0xFFFFFFFF),
  200: Color(0xFFFFFFFF),
  300: Color(0xFFFFFFFF),
  400: Color(0xFFFFFFFF),
  500: Color(0xFFFFFFFF),
  600: Color(0xFFFFFFFF),
  700: Color(0xFFFFFFFF),
  800: Color(0xFFFFFFFF),
  900: Color(0xFFFFFFFF),
    });

Answer 2

您不能将MaterialColor分配给 primaryswatch infect primaryswatch用于分配不同类型的颜色，如primaryColor、primaryColorLight/Dark、accentColor等。

您可以从类似类型的问题中获得更多详细信息。How do I use the different shades of a color swatch in Flutter?

Answer 3

您需要创建一个整体的MaterialColor对象，为十个不同的亮度值提供所有颜色值。请考虑使用此解决方案以获得更好的方法。

Flutter: Creating a custom color swatch for MaterialColor