Array adapter with custom subclass objects

Question

The solution is in the bottom:

I made some classes that i want to use in a listview. They look like this:

public class Equipment{
       ....code....
}

and

public class Weapon extends Equipment{
        ...More code...
}

and

public class Armor extends Equipment{
        ...More code...
}

As you can see weapon and armor extends equipment. Now i want to use theese classes in the same ArrayAdapter. In my imagination it would be simple as this:

public class ShopItemAdapter extends ArrayAdapter<Equipment>{
private List<Equipment> itemList;
    public ShopItemAdapter(Context context, List<Equipment> itemList) {
    super(context, android.R.layout.simple_list_item_1, itemList);
    this.itemList = itemList;
    this.context = context;
    }
     .... CODE ....
}

But for some reason I may not create an ArrayAdapter Equipment with List Weapon or List Armor.

ShopItemAdapter adapter = new ShopItemAdapter(getApplicationContext(), weaponList);

This codes gives me the error that ShopItemAdapter(Context, List) is undefined

Am I using subclasses in the wrong way or what?

My goal is to show a list of armors when clicking on a button and viseversa.

Hope my problem is clear. Thanks!

SOLUTION ** So i just needed to change the constructor to receive then cast to List in the super constructor.

public class ShopItemAdapter extends ArrayAdapter<Equipment>{
private List<Equipment> itemList;
    public ShopItemAdapter(Context context, List<? extends Equipment> itemList) {
    super(context, android.R.layout.simple_list_item_1, (List<Equipment>)itemList);
    this.itemList = (List<Equipment>)itemList;
    this.context = context;
    }
     .... CODE ....
}

Your idea is correct but the actual implementation maybe not. What is the exact problem? — Szymon
– Szymon, Commented Dec 29, 2013 at 23:48
When creating an adapter i get the error "The constructor ShopItemAdapter(Context, List<Weapon>) is undefined. Do need to create a constructor for every List types? Seems weird as Weapon extends Equipment. :( — Furedal
– Furedal, Commented Dec 30, 2013 at 14:02

laalto · Accepted Answer · 2013-12-30 14:10:54Z

1

When creating an adapter i get the error "The constructor ShopItemAdapter(Context, List) is undefined. Do need to create a constructor for every List types? Seems weird as Weapon extends Equipment. :(

No, but you need to specify that any subclass of Equipment will also do:

public ShopItemAdapter(Context context, List<? extends Equipment> itemList) {

? is a wildcard in Java generics and ? extends A makes it bound to type A or its subclasses.

answered Dec 30, 2013 at 14:10

laalto

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2 Comments

Furedal Over a year ago

I tried <? extends Equipment> but public class ShopItemAdapter extends ArrayAdapter<? extends Equipment> gives me the error "A supertype may not specify any wildcard"

Furedal Over a year ago

I tried public ShopItemAdapter(Context context, List<? extends Equipment> itemList) { worked. I just forgot to cast it to equipment when calling the super constructor. :) Thanks!

Steve M · Accepted Answer · 2013-12-29 23:59:58Z

0

Your idea is fine, but you will also have to override getView() and populate your layout there. The default is for ArrayAdapter to populate a single TextView.

answered Dec 29, 2013 at 23:59

Steve M

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1 Comment

Szymon Over a year ago

Not necessarily. If you only use fields available in Equipment, that should be ok.

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