C# Xamarin ImageURL

Question

我有3个领域的模型: TItle，身体，图片。

 public class Names
    {   [PrimaryKey]
        public string Title { get; set; }
        public string Body { get; set; }
        public string Picture { get; set; }}

字段'Picture‘是一个字符串值，它是图像url的一部分。因此，实际的URL将如下所示：

Source = Settings.ServerUrl + "/api/File/" + Picture

如何在xamarin中为imagecell的imagesource使用这样的url？

当前XAML示例：

​

当前XAML.CS示例

namespace Project.Mobile.Client.Portable.Views.Names
{
    [XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class NamesListPage : ContentPage
    {
        public ObservableCollection<Models.Names> items { get; set; }

    public NewPage()
    {
        items = new ObservableCollection<Models.Names>();
        this.BindingContext = this;
        InitializeComponent();

        // Disabling selection
        Lst.ItemSelected += (sender, e) => {
            ((ListView)sender).SelectedItem = null;
        };

        Lst.Refreshing += (sender, e) => {
            LoadUsersData();
        };
        LoadUsersData();
    }

    public async void LoadUsersData()
    {
        Lst.IsRefreshing = true;

        var names = await App.Database.Names.GetItemsAsync();
        items.Clear();


        foreach (var item in names)
            items.Add(item);

        Lst.IsRefreshing = false;
    }

    public async void OnItemTapped(object sender, ItemTappedEventArgs e)
    {
        NamesReadPage readPage = new NamesReadPage();
        readPage.BindingContext = e.Item as Models.Names;

        await Navigation.PushAsync(readPage);
    }
}

由于代码限制，我添加了xaml代码作为图像。很抱歉。

Answer 1

通过IValueConverter

public class PictureURLConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return Settings.ServerUrl + "/api/File/" + (string)value;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

添加IValueConverter的名称空间

xmlns:local="clr-namespace:SameNameSpace;assembly=SomeAssemblyName"    

将IValueConverter添加到您的ContentPage.Resources

<ContentPage.Resources>
    <ResourceDictionary>
        <local:PictureURLConverter x:Key="pictureURL"></local:PictureURLConverter>
    </ResourceDictionary>
</ContentPage.Resources>

在绑定中使用转换器

<Image Source="{Binding Picture, Converter={StaticResource pictureURL}}" />

Answer 2

创建一个viewModel并更改属性以返回所需的url，然后将此属性绑定到您的Image Source。

public string PictureUrl
{
    get
    {
        return Settings.ServerUrl + "/api/File/" + this.PictureUrl;
    }
    set
    {
        this.PictureUrl = value;
        OnPropertyChanged("PictureUrl");
    }
}