Why can't one add/remove items from an ArrayAdapter?
I am using an ArrayAdapter<CharSequence>
to populate the items to list in a android.widget.Spinner
. That works all fine.
But now I want to keep the list of items dynamic, i.e. I want to be able to add/remove items from the selection list at runtime. However, when I call adapter.add(item)
or adapter.remove(item)
I always get a UnsupportedOperationException
, even though the Javadocs of the ArrayAdapter
class describe these two methods as to be usable for exactly that intended purpose.
Is this a bug, really not implemented or what am I missing here?
You probably initialized the adapter with a plain Java array (e.g., String[]
). Try using something that implements the java.util.List
interface (e.g., ArrayList<String>
).
I know it's late but just a quick explanation: it's because method Arrays.asList(T... array) returns custom inner class named ArrayList that is read-only. As already said, you need to provide full impl. e.g. java.util.ArrayList.
Here's the source code of ArrayAdapter#remove
:
public void remove(T object) {
if (mOriginalValues != null) {
synchronized (mLock) {
mOriginalValues.remove(object);
}
} else {
mObjects.remove(object);
}
if (mNotifyOnChange) notifyDataSetChanged();
}
The only thing that can throw an UnsupportedOperationException
there is the line in the else-block. So the problem is that the list you're using doesn't support removing items. My guess is you're using an array. Try an ArrayList, for instance.
edit: So yeah, what Mark said...
I was having the same problem, my data was saved in resource String Array, so I was creating ArraAdapter with createFromResource.
The following code for creating ArrayAdapter from resource String Array solved the problem:
Resources res = getResources();
String[] cities = res.getStringArray(R.array.cities_array);
ArrayAdapter<CharSequence> adapter = new ArrayAdapter(
this,
android.R.layout.simple_spinner_item,
new ArrayList(Arrays.asList(cities)));
In your adapter Class - Delete an Item
remove(position);
notifyDataSetChanged();
Add an Item -
adapter.add (newItem);
adapter.notifyDataSetChanged ();