为选择器中的项添加键值

Question

我正在使用XAMARIN选择器来选择国家/地区.这些国家在选择器中进行了硬编码.有没有办法通过键值识别每个国家/地区名称.我使用SAPUI5以类似的方式完成了这项工作.

<core:Item key="AF" text="Afghanistan  " />
<core:Item key="AL" text="Albania  " />
<core:Item key="DZ" text="Algeria  " />
<core:Item key="VI" text="Amer.Virgin Is. " />

类似地,我有办法在XAMARIN表单选择器中为每个国家/地区添加键值吗？

Answer 1

有一种方法可以使用数据绑定在Picker中使用Key-Value-Pairs.

首先,您必须在窗体的视图模型中定义字典,并定义一个返回字典键值对的列表的属性.还需要绑定到当前选定的项目:

class MyViewModel
{
  ...
  private Dictionary<string, string> PickerItems = 
    new Dictionary<string, string>() { {"AF", "Afghanistan"}, {"AL", "Albania" } };

  public List<KeyValuePair<string, string>> PickerItemList
  {
      get => PickerItems.ToList();
  }

  private KeyValuePair<string, string> _selectedItem;
  public KeyValuePair<string, string> SelectedItem
  {
      get => _selectedItem;
      set => _selectedItem = value;
  }
  ...
}

其次,你必须在Pickers定义中设置Pickers ItemsSource,ItemDisplayBinding和SelectedItem Bindings:

<Picker
    ItemDisplayBinding="{Binding Value}"
    ItemsSource="{Binding PickerItemList}"
    SelectedItem="{Binding SelectedItem}" />

鉴于此,您可以在View Model中获取所选项的键

SelectedItem.Key

进一步阅读:https://developer.xamarin.com/guides/xamarin-forms/user-interface/picker/populating-itemssource/#Populating_a_Picker_with_Data_Using_Data_Binding

Answer 2

我刚刚面临同样的问题，我找到了一种方法来做到这一点。我只需要将选择器与元素列表绑定SomeClass。这是我所做的：

namespace MyApp.ViewModels 
{
    public class CboViewModel 
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }
}

然后在我的XAML文件中：

<ContentPage ...
    xmlns:vm="clr-namespace:MyApp.ViewModels;assembly=Myapp" >
    <ContentPage.Content>
        ...
        <Picker x:Name="pckStatus" HorizontalOptions="FillAndExpand" >
            <Picker.ItemsSource>
                <x:Array Type="{x:Type vm:CboViewModel}" >
                    <vm:CboViewModel Id="0" Name="All" />
                    <vm:CboViewModel Id="1" Name="New" />
                    <vm:CboViewModel Id="2" Name="Standby" />
                    <vm:CboViewModel Id="4" Name="In Progress" />
                    <vm:CboViewModel Id="8" Name="Submitted" />
                    <vm:CboViewModel Id="16" Name="Closed" />
                </x:Array>
            </Picker.ItemsSource>
            <Picker.ItemDisplayBinding>
                <Binding Path="Name" />
            </Picker.ItemDisplayBinding>
            <Picker.SelectedIndex>0</Picker.SelectedIndex>
        </Picker>
        ...
    <ContentPage.Content>
</ContentPage>

Answer 3

不，关键属性在 xamarin 选择器中可用。但是，您可以使用 xamarin 选择器类的 Dictionary 类和 SelectedIndex 属性来实现它。

使用以下代码片段实现它：

class PickerDemoPage : ContentPage
        {
            // Dictionary to get Color from color name.
            Dictionary<string, Color> nameToColor = new Dictionary<string, Color>
            {
                { "Aqua", Color.Aqua }, { "Black", Color.Black },
                { "Blue", Color.Blue }, { "Fuschia", Color.Fuschia },
                { "Gray", Color.Gray }, { "Green", Color.Green },
                { "Lime", Color.Lime }, { "Maroon", Color.Maroon },
                { "Navy", Color.Navy }, { "Olive", Color.Olive },
                { "Purple", Color.Purple }, { "Red", Color.Red },
                { "Silver", Color.Silver }, { "Teal", Color.Teal },
                { "White", Color.White }, { "Yellow", Color.Yellow }
            };

            public PickerDemoPage()
            {
                Label header = new Label
                {
                    Text = "Picker",
                    FontSize = Device.GetNamedSize (NamedSize.Large, typeof(Label)),
                    HorizontalOptions = LayoutOptions.Center
                };

                Picker picker = new Picker
                {
                    Title = "Color",
                    VerticalOptions = LayoutOptions.CenterAndExpand
                };

                foreach (string colorName in nameToColor.Keys)
                {
                    picker.Items.Add(colorName);
                }

                // Create BoxView for displaying picked Color
                BoxView boxView = new BoxView
                {
                    WidthRequest = 150,
                    HeightRequest = 150,
                    HorizontalOptions = LayoutOptions.Center,
                    VerticalOptions = LayoutOptions.CenterAndExpand
                };

                picker.SelectedIndexChanged += (sender, args) =>
                    {
                        if (picker.SelectedIndex == -1)
                        {
                            boxView.Color = Color.Default;
                        }
                        else
                        {
                            string colorName = picker.Items[picker.SelectedIndex];
                            boxView.Color = nameToColor[colorName];
                        }
                    };

                // Accomodate iPhone status bar.
                this.Padding = new Thickness(10, Device.OnPlatform(20, 0, 0), 10, 5);

                // Build the page.
                this.Content = new StackLayout
                {
                    Children =
                    {
                        header,
                        picker,
                        boxView
                    }
                };

            }
        }

来源：https : //developer.xamarin.com/api/type/Xamarin.Forms.Picker/