如何在WPF XAML中制作加载图形？

Question

所以我有一个小的WPF XAML,它获取我的RSS提要的标题,并将它们放在ListBox中.

但是,加载大约需要2秒钟.

我怎么能在ListBox中放置某种AJAXy旋转图形,直到数据存在？

这是代码:

<Window x:Class="WpfApplication5.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300">
    <StackPanel>
        <StackPanel.Resources>
            <XmlDataProvider x:Key="ExternalColors" Source="http://www.tanguay.info/web/rss" XPath="/"/>
        </StackPanel.Resources>
        <TextBlock Text="RSS Feeds:"/>
        <ListBox Name="lbColor" Height="200" IsSynchronizedWithCurrentItem="True" ItemsSource="{Binding Source={StaticResource ExternalColors}, XPath=//item/title}"/>

        <TextBlock Text="You selected this feed:"/>
        <TextBox
            Text="{Binding ElementName=lbColor, Path=SelectedValue}"
            Background="{Binding ElementName=lbColor, Path=SelectedValue}">
        </TextBox>
    </StackPanel>
</Window>

Answer 1

我的解决方案是在我的数据和WPF之间实现异步层.这完全解除了WPF与数据端的任何延迟,并为我提供了很好的事件和属性来触发和绑定.

我在View Model或Presenter Model架构之上构建了它.我写了一篇关于基础知识的博客文章,以及关于异步View模型方法的更长篇幅.

这是微调器的XAML.在DataContext它需要进行加载的View Model.根据它State,它LoadingIndicator将使自己可见并再次崩溃.

<UserControl x:Class="App.WPF.CustomControls.LoadingIndicator"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             Height="20"
             Width="20">
    <UserControl.Style>
        <Style TargetType="{x:Type UserControl}">
            <Style.Triggers>
                <DataTrigger Binding="{Binding State}"
                             Value="Active">
                    <Setter Property="Visibility"
                            Value="Collapsed" />
                </DataTrigger>
                <DataTrigger Binding="{Binding State}"
                             Value="Loading">
                    <Setter Property="Visibility"
                            Value="Visible" />
                </DataTrigger>
                <DataTrigger Binding="{Binding State}"
                             Value="Invalid">
                    <Setter Property="Background"
                            Value="Red" />
                    <Setter Property="Visibility"
                            Value="Visible" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </UserControl.Style>
    <UserControl.Triggers>
        <EventTrigger RoutedEvent="UserControl.Loaded">
            <BeginStoryboard>
                <Storyboard TargetName="Rotator"
                            TargetProperty="Angle">
                    <DoubleAnimation By="360"
                                     Duration="0:0:2"
                                     RepeatBehavior="Forever" />
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
    </UserControl.Triggers>
    <Rectangle Stroke="Aqua"
               StrokeThickness="2"
               Width="10"
               Height="10">
        <Rectangle.RenderTransform>
            <RotateTransform x:Name="Rotator"
                             Angle="0"
                             CenterX="5"
                             CenterY="5" />
        </Rectangle.RenderTransform>
    </Rectangle>
</UserControl>

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