IndexOutOfBoundsException after filtering adapter - xamarin.android

Question

I have an autocomplete control that'll be drawing from an api to build the autocomplete dropdown list. I have everything wired up but I get this error while typing:
03-26 13:41:40.546 E/AndroidRuntime(31931): java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
03-26 13:41:40.546 E/AndroidRuntime(31931): at java.util.ArrayList.get(ArrayList.java:437)
03-26 13:41:40.546 E/AndroidRuntime(31931): at android.widget.ArrayAdapter.getItem(ArrayAdapter.java:385)
03-26 13:41:40.546 E/AndroidRuntime(31931): at android.widget.AutoCompleteTextView.buildImeCompletions(AutoCompleteTextView.java:1243)
03-26 13:41:40.546 E/AndroidRuntime(31931): at android.widget.AutoCompleteTextView.showDropDown(AutoCompleteTextView.java:1203)
03-26 13:41:40.546 E/AndroidRuntime(31931): at android.widget.AutoCompleteTextView.updateDropDownForFilter(AutoCompleteTextView.java:1086)
03-26 13:41:40.546 E/AndroidRuntime(31931): at android.widget.AutoCompleteTextView.onFilterComplete(AutoCompleteTextView.java:1068)
03-26 13:41:40.546 E/AndroidRuntime(31931): at android.widget.Filter$ResultsHandler.handleMessage(Filter.java:285)
03-26 13:41:40.546 E/AndroidRuntime(31931): at android.os.Handler.dispatchMessage(Handler.java:106)
03-26 13:41:40.546 E/AndroidRuntime(31931): at android.os.Looper.loop(Looper.java:164)
03-26 13:41:40.546 E/AndroidRuntime(31931): at android.app.ActivityThread.main(ActivityThread.java:6494)
03-26 13:41:40.546 E/AndroidRuntime(31931): at java.lang.reflect.Method.invoke(Native Method)>
03-26 13:41:40.546 E/AndroidRuntime(31931): at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
03-26 13:41:40.546 E/AndroidRuntime(31931): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
My Adapter Class
public class UserFilterAdapter : ArrayAdapter<UserAutoComplete>, IFilterable
{
private readonly Context _context;
private readonly int _textViewResourceId;
private readonly Filter _filter;
private List<UserAutoComplete> _userAutoComplete;
public override int Count => _userAutoComplete?.Count ?? 0;
public override Filter Filter => _filter;
public DirectoryOrgUnitFilterAdapter(List<UserAutoComplete> userAutoComplete, Context context, int textViewResourceId) : base(context, textViewResourceId)
{
_context = context;
_filter = new UserAutoCompleteFilter(this);
_textViewResourceId = textViewResourceId;
_userAutoComplete = userAutoComplete;
}
public void RefreshAdapter(List<UserAutoComplete> userAutoComplete)
{
_userAutoComplete = userAutoComplete;
NotifyDataSetChanged();
}
public override View GetView(int position, View convertView, ViewGroup parent)
{
if (convertView == null)
{
var inflater = (LayoutInflater) _context.GetSystemService(Context.LayoutInflaterService);
convertView = inflater.Inflate(_textViewResourceId, parent, false);
}
var itemName = convertView.FindViewById<TextView>(Resource.Id.user_autocomplete_item_name);
var itemType = convertView.FindViewById<TextView>(Resource.Id.user_autocomplete_item_type);
var item = GetItem(position);
itemName.Text = item.UserName;
itemType.Text = item.Email;
return convertView;
}
}
My Filter Class
public class UserAutoCompleteFilter : Filter
{
private readonly UserFilterAdapter _adapter;
public UserAutoCompleteFilter(UserFilterAdapter adapter)
{
_adapter = adapter;
}
protected override FilterResults PerformFiltering(ICharSequence constraint)
{
var results = new FilterResults();
if (string.IsNullOrEmpty(constraint?.ToString()))
{
return results;
}
var searchFor = constraint.ToString();
if (searchFor.Length < 3)
{
return results;
}
var matches = ApiService.GetUsers(searchFor).ConfigureAwait(false).GetAwaiter().GetResult();
results.Values = FromArray(matches.Select(r => r.ToJavaObject()).ToArray());
results.Count = matches.ToList().Count;
constraint.Dispose();
return results;
}
protected override void PublishResults(ICharSequence constraint, FilterResults results)
{
if (results?.Values == null)
{
return;
}
using (var values = results.Values)
{
_adapter.RefreshAdapter(values.ToArray<Object>().Select(a => a.ToNetObject<UserAutoComplete>()).ToList());
}
constraint.Dispose();
results.Dispose();
}
}
I debugged through the logic and the filtering is getting hit and returning data, so I'm lost on where it's losing the data and throwing an out of bounds exception.
I've followed this tutorial on getting filtering to work in C# and then this tutorial on applying it to an autocomplete textview control.

Answer 1

I finally got it working. The key problem was that my adapter was using ArrayAdapter instead of BaseAdapter.
once I switched that out, it works as intended, not sure why I can't use ArrayAdapter but I'm thrilled that my autocomplete control is finally working.