json - Flutter:如何根据声明为JSON显示的数据着色

Question

这是json文件

[
  {
    "id": 1,
    "country": "United States",
    "continent": "North America"
  },
  {
    "id": 2,
    "country": "Germany",
    "continent": "Europe"
  },
  {
    "id": 3,
    "country": "United Kingdom",
    "continent": "Europe"
  }
]

我要设置条件如下:

1.北美(美国)的国家/地区将使用
CotinentColor.NA 2.欧洲国家(德国和英国)
将使用CotinentColor.EU

那我该怎么办？

这是custom_color文件

import 'package:flutter/material.dart';

class ContinentColor {
  static const Color NA = Color(0xFFFF9E80);
  static const Color EU = Color(0xFF2196F3);
  static const Color Asia = Color(0xFFE0E0E0);
}

这是主文件:

                        ListView.builder(
                            itemCount: countries.length,
                            itemBuilder: (context, index) {
                              return Padding(
                                  padding: const EdgeInsets.all(5.0),
                                  child: Column(children: <Widget>[
                                    Text(
                                      countries[index].country,
                                      style: const TextStyle(
                                          color:,
                                          // How to apply color according follow the conditional
                                    )
                                  ]));
                            });

Answer 1

为了避免样板，可以创建扩展方法，如下所示:

extension ContinentExtension on String {
  Color get color{
    switch (this.toUpperCase()) {
      case "EUROPE":
        return ContinentColor.EU;
      case "NORTH AMERICA":
        return ContinentColor.NA;
      case "ASIA":
        return ContinentColor.Asia;
      default:
        return Color(0xFFFFFFFF);
    }
  }
}

String americaCon = "North America";

print("Europe".color);
print(americaCon.color);

color: countries[index].continent.color;

对于 Assets 文件名映射，请尝试以下方式:

extension AssetsExtension on String {
  String get asset => this.toLowerCase().replaceAll(" ", "_");
}

main(){
  print("North America".asset); //north_america
  print("Europe".asset); //europe
}