由静态final类实现的java抽象字段？

Question

我正在尝试为我的Android应用程序创建自定义调色板。我开始这样做：

public class Theme {

    public static final class DARK {
        final static int POSITIVE_GREEN = Color.rgb(0, 200, 0);
        final static int NEGATIVE_RED = Color.rgb(200, 0, 0);
        final static int BACKGROUND_GREEN = Color.argb(255 - 220, 0, 255, 0); //220
        final static int BACKGROUND_RED = Color.argb(255 - 220, 255, 0, 0);
    }

    public static final class PASTEL {
        final static int POSITIVE_GREEN = Color.parseColor("#326262");
        final static int NEGATIVE_RED = etc
        final static int BACKGROUND_GREEN = etc
        final static int BACKGROUND_RED = etc
    }

}

但当我想重构其中一个字段名时，我意识到有点不对劲。字段名在主题或其他方面应该是抽象的，但由于它们不应该是可实例化的类，我不能使用这里建议的构造函数技巧： Why not abstract fields? 我该怎么做

Answer 1

如果你只是想使用一个合同的名称，你可以使用下面的概念

public interface Theme {
    public int POSITIVE_GREEN;
    public int NEGATIVE_RED;
    public int BACKGROUND_GREEN;
    public int BACKGROUND_RED;
    public Color getColor(int colorName);
}

public static final class Theme1 extends Theme {
    Map<Integer, Color> colorMap = new HashMap<>();
    private Theme1() {
        colorMap.put(POSITIVE_GREEN, Color.rgb(0, 200, 0));
        colorMap.put(NEGATIVE_RED, Color.rgb(200, 0, 0));
        colorMap.put(BACKGROUND_GREEN, Color.argb(255 - 220, 0, 255, 0));
        colorMap.put(BACKGROUND_RED, Color.argb(255 - 220, 255, 0, 0));
    }

    @Override
    public Color getColor(int colorName) {
        return colorMap.get(colorName);
    }
}

Answer 2

使用枚举而不是int常量 您可以改用enum，例如：

public enum DARK {
        POSITIVE_GREEN (0,200, ..){
              void abstractField(){
                 //Achieve your custom methods
              }
        },
        NEGATIVE_RED (200,0, ..){
           //Achieve your custom methods
        },
        BACKGROUND_GREEN (.....){
           //Achieve your custom methods
        },
        BACKGROUND_RED (...){
          //Achieve your custom methods
        },
      

       // Offer (with the Senate) constructor to initialize the fields defined
       DARK (int variable1, int variable2) {
                this.variable1 = variable1;
                this.variable2 = variable2;
       }
       // Define the fields you need
       private int variable1;
       private int variable2;

       //Custom abstract methods you need
       abstract void abstartField();
}

我不知道你是否能帮忙

Answer 3

在这里使用接口似乎合适：

每个主题都将实现这个界面：

public interface Theme {
    int getPositiveGreen(); 
    ...
}

例如：

public class Dark implements Theme {

   private final static int POSITIVE_GREEN = Color.rgb(0, 200, 0);

   public int getPositiveGreen() {
       return POSITIVE_GREEN;
   }
   ....
}

一般来说，公共静态变量的使用应该局限于一些非常简单的场景，而这并不是您想要实现的

https://docs.oracle.com/javase/tutorial/java/concepts/interface.html

Answer 4

抽象方法只是子类需要提供的函数

“抽象字段”也可以被认为是一个需要提供的值

public class Theme {

    public final int POSITIVE_GREEN;
    public final int NEGATIVE_RED;
    public final int BACKGROUND_GREEN;
    public final int BACKGROUND_RED;

    private Theme(int POSITIVE_GREEN, int NEGATIVE_RED, int BACKGROUND_GREEN, int BACKGROUND_RED)
    {
        this.POSITIVE_GREEN = POSITIVE_GREEN;
        this.NEGATIVE_RED = NEGATIVE_RED;
        this.BACKGROUND_GREEN = BACKGROUND_GREEN;
        this.BACKGROUND_RED = BACKGROUND_RED;
    }

    public static final Theme DARK = new Theme(
        Color.rgb(0, 200, 0),
        Color.rgb(200, 0, 0),
        Color.argb(255 - 220, 0, 255, 0),
        Color.argb(255 - 220, 255, 0, 0)
    );

    public static final Theme PASTEL = new Theme( ...