如何关闭焦点？

Question

如何关注品牌和颜色？我之前选择了颜色或品牌，然后输入注册

private void InitializePage()
{
    RegistrationNumberEntry.Completed += (s, e) => BrandListPicker.Focus();
    BrandListPicker.SelectedIndexChanged += (s, e) => ColorListPicker.Focus();

    BindingContext = new RegisterDetailsPageViewModel(Navigation);
}