android-自定义微调数组适配器getDropDownView返回null

public class CustomArrayAdapter extends ArrayAdapter<String> {
    private Context context;
    private String[] items;

    public CustomArrayAdapter(Context context, String[] items) {
        super(context, android.R.layout.simple_spinner_item, items);
        this.context = context;
        this.items = items;
    }

    @Override
    public View getDropDownView(int position, View convertView, ViewGroup parent) {
        LayoutInflater inflater = LayoutInflater.from(context);
        View view = inflater.inflate(R.layout.dropdown_item, parent, false);
        
        TextView textView = view.findViewById(R.id.dropdown_text);
        textView.setText(items[position]);
        
        return view;
    }
}