A simple way of limiting auto complete choices to a finite set

FiniteAutoCompleteTextView.java

import android.annotation.TargetApi;
import android.content.Context;
import android.content.res.Resources;
import android.os.Build;
import android.util.AttributeSet;
import android.widget.AutoCompleteTextView;
import android.widget.Filter;
import android.widget.Filterable;
import android.widget.ListAdapter;

public class FiniteAutoCompleteTextView extends AutoCompleteTextView {
    public FiniteAutoCompleteTextView(Context context) {
        super(context);
    }

    public FiniteAutoCompleteTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public FiniteAutoCompleteTextView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    public FiniteAutoCompleteTextView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    @TargetApi(Build.VERSION_CODES.N)
    public FiniteAutoCompleteTextView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes, Resources.Theme popupTheme) {
        super(context, attrs, defStyleAttr, defStyleRes, popupTheme);
    }

    @Override
    public <T extends ListAdapter & Filterable> void setAdapter(T adapter) {
        super.setAdapter(adapter);
        setValidator(new FiniteValidator<>(adapter));
    }

    public class FiniteValidator<T extends ListAdapter & Filterable> implements AutoCompleteTextView.Validator {

        private T adapter;

        public FiniteValidator(T adapter) {
            this.adapter = adapter;
        }

        @Override
        public boolean isValid(CharSequence charSequence) {
            Filter filter = adapter.getFilter();
            for (int i = 0; i < adapter.getCount(); i++) {
                Object item = adapter.getItem(i);
                CharSequence stringItem = filter.convertResultToString(item);
                if (stringItem.toString().equals(charSequence.toString())) {
                    return true;
                }
            }
            return false;
        }

        @Override
        public CharSequence fixText(CharSequence charSequence) {
            Filter filter = adapter.getFilter();
            for (int i = 0; i < adapter.getCount(); i++) {
                Object item = adapter.getItem(i);
                CharSequence stringItem = filter.convertResultToString(item);
                if (stringItem.toString().toUpperCase().equals(charSequence.toString().toUpperCase())) {
                    return stringItem;
                }
            }
            return null;
        }
    }
}