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, Dec 29 '13 at 23:48
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. :( — Furedal, Dec 30 '13 at 14:02

score 1 · Accepted Answer · answered Dec 30 '13 at 14:10

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 '13 at 14:10

laalto

150,114
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I tried extends Equipment> but public class ShopItemAdapter extends ArrayAdapter extends Equipment> gives me the error "A supertype may not specify any wildcard" – Furedal Dec 30 '13 at 14:24
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! – Furedal Dec 30 '13 at 14:28

score 0 · Answer 2 · answered Dec 29 '13 at 23:59

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 '13 at 23:59

Steve M

9,296
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Not necessarily. If you only use fields available in `Equipment`, that should be ok. – Szymon Dec 30 '13 at 00:01

Array adapter with custom subclass objects

2 Answers2