渲染操作处于活动状态时,应用程序窗口会阻塞.
即何时设置ContentControl的Content属性.绘制用户控件,该用户控件是内容的DataTemplate.冻结持续5到10秒,具体取决于所使用的PC.

这个用户控件不是太复杂(大约250个简单的控件 – 图像,文本框,文本块,按钮等).布局远非完美,我没有写,我既没有时间,也没有优化布局,因为问题最多可以减少.

我能够完成的最好的事情是将控件包装在一个’容器’中,该容器设法绘制一个加载动画并在ui / app窗口冻结之前显示一个忙碌的光标.
我在下面给出了完整的代码清单.

我在代码中评论了“在这里开始冻结”,在包装器自定义控件代码的问题的底部.那时WPF渲染引擎开始绘制用户控件(即其中的网格).

我经常使用我最喜欢的搜索引擎,并且我了解到WPF有一个特殊的’render’线程,它与UI线程分开.

其他在冻结时隐藏App窗口并在此期间显示“加载”动画窗口(或其中的一些衍生物),这很容易给出下面的代码但是很荒谬 – 是否有某种方法可以缓解这种情况？

这是代码,首先是用例：

<!-- while I am being rendered, I block the UI thread. -->
<UserControl x:Class="MyUserControl"
             xmlns:loading="clr-namespace:Common.UI.Controls.Loading;assembly=Common.UI.Controls">    
    <loading:VisualElementContainer>
        <loading:VisualElementContainer.VisualElement>
            <Grid>
                <!-- some 500 lines of using other controls with binding, templates, resources, etc.. 
                for the same effect try having a canvas with maaany rectangles..-->
            </Grid>
        </loading:VisualElementContainer.VisualElement>
    </loading:VisualElementContainer>    
</UserControl>

包装器自定义控件布局：

<Style TargetType="{x:Type loading:VisualElementContainer}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type loading:VisualElementContainer}">
                <Border Background="{TemplateBinding Background}"
                        BorderBrush="{TemplateBinding BorderBrush}"
                        BorderThickness="{TemplateBinding BorderThickness}">
                    <Grid>
                        <loading:LoadingAnimation x:Name="LoadingAnimation" VerticalAlignment="Center" HorizontalAlignment="Center"/>
                        <ContentControl x:Name="ContentHost"/>
                    </Grid>
                </Border>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

和包装器自定义控制代码：

/// <summary>Hosts the visual element and displays a 'loading' animation and busy cursor while it is being rendered.</summary>
public class VisualElementContainer : Control
{
    static VisualElementContainer()
    {
        DefaultStyleKeyProperty.OverrideMetadata(typeof(VisualElementContainer), new FrameworkPropertyMetadata(typeof(VisualElementContainer)));
    }

    private Window MyWindow;
    private ContentControl ContentHost;
    private LoadingAnimation LoadingAnimation;

    public override void OnApplyTemplate()
    {
        this.ContentHost = this.GetTemplateChild("ContentHost") as ContentControl;
        this.LoadingAnimation = this.GetTemplateChild("LoadingAnimation") as LoadingAnimation;

        base.OnApplyTemplate();

        this.MyWindow = this.FindVisualParent(typeof(Window)) as Window;

        this.SetVisual(this.VisualElement);
    }

    private static DependencyProperty VisualElementProperty =
        DependencyProperty.Register(
            "VisualElement",
            typeof(FrameworkElement),
            typeof(VisualElementContainer),
            new PropertyMetadata(null, new PropertyChangedCallback(VisualElementPropertyChanged)));

    public FrameworkElement VisualElement
    {
        get { return GetValue(VisualElementProperty) as FrameworkElement; }
        set { SetValue(VisualElementProperty, value); }
    }

    private static void VisualElementPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        var me = sender as VisualElementContainer;

        if (me == null || me.ContentHost == null || me.LoadingAnimation == null)
            return;

        me.RemoveVisual(e.OldValue as FrameworkElement);
        me.SetVisual(e.NewValue as FrameworkElement);
    }

    private void RemoveVisual(FrameworkElement fwElement)
    {
        this.ContentHost.Content = null;

        if (fwElement != null)
            fwElement.Loaded -= fwElement_Loaded;
    }

    private void SetVisual(FrameworkElement fwElement)
    {
        if (fwElement == null)
        {
            this.ContentHost.Content = fwElement;
        }
        else
        {
            fwElement.Loaded += fwElement_Loaded;

            this.SetContentVisibility(false);

            this.Dispatcher
                .BeginInvoke(
                //freeze begins here
                    new Action(() => this.ContentHost.Content = fwElement),
                    System.Windows.Threading.DispatcherPriority.ContextIdle);
        }
    }

    private void fwElement_Loaded(object sender, RoutedEventArgs e)
    {
        this.SetContentVisibility(true);
        //freeze ends here.
    }

    private void SetContentVisibility(bool isContentVisible)
    {
        if (isContentVisible)
        {
            this.MyWindow.Cursor = Cursors.Arrow;

            this.LoadingAnimation.Visibility = Visibility.Collapsed;
            this.ContentHost.Visibility = Visibility.Visible;
        }
        else
        {
            this.MyWindow.Cursor = Cursors.Wait;

            this.ContentHost.Visibility = Visibility.Hidden; //Setting to collapsed results in the loaded event never fireing. 
            this.LoadingAnimation.Visibility = Visibility.Visible;
        }
    }
}

解决方法:

我真的不认为你的问题实际上与渲染或布局有关.特别是只有250个控件,因为我看到wpf咀嚼100次以上没有任何问题(它的渲染引擎效率低但效率不高).除非你滥用丰富的效果(位图效果,不透明蒙版)与糟糕的硬件或糟糕的驱动程序,或做一些非常奇怪的事情.

考虑您需要的所有数据.是否有从磁盘加载的大图像或其他大型资源？网络运营？长计算？

根据答案,可以将某些任务推迟到另一个线程.但是没有更多信息,我可以建议的唯一解决方案是使用HostVisual来嵌套将存在于另一个线程中的控件.不幸的是,这仅适用于非交互式儿童(不需要接收用户输入的儿童).