Android abstract parcelable class

Question

Problem Description

I have Category class which implements Parcelable , also I have few more classes which are extended from the Category class. My base class has 2 protected members title and id which are set mainly from the inherited classes. So in order not to implement Parcelable related stuff everywhere in the inherited classes I decide to do it in a base class and let it handle all actions.

Question

The problem is that I can't have constructor of Category class as it is abstract class. So what is the solution? As I have abstract methods in the class I can't remove abstract modifier.

Source code

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

It is possible to have constructors in abstract classes, and you can do the parceling there - just make sure you call the respective super(...) method in the child classes. Check this out.

EDIT: I think Category does not need to implement CREATOR as you cannot instantiate it...? Similar suggestions are here and 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];
        }
    };
};