Android 抽象可打包类

Question

问题描述

我有实现Parcelable 的Category 类，还有一些从Category 类扩展而来的类。我的基类有 2 个protected 成员title 和id，它们主要是从继承的类中设置的。因此，为了不在继承的类中到处实现Parcelable 相关的东西，我决定在基类中执行它并让它处理所有操作。

问题

问题是我不能拥有Category 类的构造函数，因为它是抽象类。那么解决方案是什么？由于我在类中有抽象方法，因此无法删除抽象修饰符。

源代码

public abstract class Category implements Parcelable {
    private static Map<Integer, Category> categoryMap = new TreeMap<Integer, Category>();

    protected Sting title;
    protected Integer  id;

    static {
        categoryMap.put(0, new Taxi());
        categoryMap.put(1, new Hotel());
    }

    private Category(Parcel in) {
        this.id = in.readInt();
        this.title = in.readString();
    }

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeInteger(id);
        dest.writeString(title);
    }
    
    public static final Parcelable.Creator<Category > CREATOR = new Parcelable.Creator<Category >() {
        public Category createFromParcel(Parcel in) {
            return new Category (in);  <=== !!! THIS IS NOT ALLOWED AS CLASS IS ABSTRACT !!!
        }                          

        public Category [] newArray(int size) {
            return new Category[size];
        }
    };

    abstract void generateCodes();
    abstract String getImageIcon();
    
};

public final class Taxi extends Category {

    public Taxi() {
        title = "taxi";
        id = 1547845;
    }

};

public final class Hotel extends Category {

    public Hotel() {
        title = "hotel";
        id = 1397866;
    } 

};

Answer 1

可以在抽象类中使用构造函数，您可以在那里进行打包 - 只需确保在子类中调用相应的 super(...) 方法即可。 签出this。

编辑： 我认为 Category 不需要实现 CREATOR 因为你不能实例化它......？类似的建议是here 和here

public abstract class Category implements Parcelable {
    private static Map<Integer, Category> categoryMap = new TreeMap<Integer, Category>();

    protected String title;
    protected Integer  id;

    static {
        categoryMap.put(0, new Taxi());
        categoryMap.put(1, new Hotel());
    }

    protected Category(){}

    protected Category(Parcel in) {
        this.id = in.readInt();
        this.title = in.readString();
    }

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeInteger(id);
        dest.writeString(title);
    }

    abstract void generateCodes();
    abstract String getImageIcon();

};

public final class Taxi extends Category {
    public Taxi() {
        title = "taxi";
        id = 1547845;
    }

    protected Taxi(Parcel in) {
        super(in);
    }

    public static final Parcelable.Creator<Taxi> CREATOR = new Parcelable.Creator<Taxi>() {
        public Category createFromParcel(Parcel in) {
            return new Taxi (in);
        }

        public Category [] newArray(int size) {
            return new Taxi[size];
        }
    };
};

public final class Hotel extends Category {
    public Hotel() {
        title = "hotel";
        id = 1397866;
    }

    protected Hotel(Parcel in) {
        super(in);
    }

    public static final Parcelable.Creator<Hotel> CREATOR = new Parcelable.Creator<Hotel>() {
        public Category createFromParcel(Parcel in) {
            return new Hotel (in);
        }

        public Category [] newArray(int size) {
            return new Hotel[size];
        }
    };
};