Helper

public class MyAdapter extends BaseAdapter implements ThemedSpinnerAdapter {
    private final ThemedSpinnerAdapter.Helper mDropDownHelper;

    public CheeseAdapter(Context context) {
        mDropDownHelper = new ThemedSpinnerAdapter.Helper(context);
        // ...
    }

    @Override
    public View getDropDownView(int position, View convertView, ViewGroup parent) {
        View view;

        if (convertView == null) {
            // Inflate the drop down using the helper's LayoutInflater
            LayoutInflater inflater = mDropDownHelper.getDropDownViewInflater();
            view = inflater.inflate(R.layout.my_dropdown, parent, false);
        }

        // ...
    }

    @Override
    public void setDropDownViewTheme(@Nullable Resources.Theme theme) {
        // Pass the new theme to the helper
        mDropDownHelper.setDropDownViewTheme(theme);
    }

    @Override
    public Resources.Theme getDropDownViewTheme() {
        // Return the helper's value
        return mDropDownHelper.getDropDownViewTheme();
    }
}