renderTargetBitmap.RenderAsync 忽略 UserContol 上的图像
renderTargetBitmap.RenderAsync Ignores Image on UserContol
我有一个这样的用户控件：
<UserControl x:Name="taskcard"
x:Class="AYOS_IDPrinter_UWP.TaskCard"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:AYOS_IDPrinter_UWP"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
HorizontalAlignment="Stretch" VerticalAlignment="Stretch" RequestedTheme="Default" Width="486" Height="306">
<UserControl.Resources>
<SolidColorBrush x:Key="AuSupportColor" Color="#FFE5C97C"/>
</UserControl.Resources>
<Grid x:Name="MainGrid" Background="White" Margin="0,0,0,0" RequestedTheme="Default">
<Grid x:Name="Skeleton" Margin="10,10,10,10" BorderThickness="2,2,2,2" BorderBrush="{StaticResource AuSupportColor}">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid x:Name="NeedleArea" BorderThickness="0,0,0,2" BorderBrush="{StaticResource AuSupportColor}" Background="{StaticResource AUColor}" Margin="0,0,0,0">
<TextBlock x:Name="Label" TextWrapping="Wrap" Text="İğne Alanı / Needle Area" Foreground="White" TextAlignment="Center" VerticalAlignment="Center" FontFamily="Noto Sans" FontWeight="Normal" Style="{StaticResource CaptionTextBlockStyle}" Margin="0,4,0,5"/>
</Grid>
<Grid x:Name="Datas" HorizontalAlignment="Stretch" Margin="10,10,10,10" VerticalAlignment="Stretch" Grid.Row="1">
<Grid.RowDefinitions>
<RowDefinition Height="*"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
</Grid.RowDefinitions>
<Grid x:Name="Name_Task_Area" HorizontalAlignment="Stretch" Margin="0,5,0,5" VerticalAlignment="Stretch" Grid.Row="1">
<Grid.RowDefinitions>
<RowDefinition Height="*"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
</Grid.RowDefinitions>
<TextBlock x:Name="NameText" Margin="0,0,0,0" TextWrapping="Wrap" TextAlignment="Center" Foreground="Red" Text="BERK BABADOĞAN" FontWeight="Bold" FontFamily="Noto Sans" Style="{StaticResource SubtitleTextBlockStyle}"/>
<TextBlock x:Name="TaskText" Margin="0,0,0,0" TextWrapping="Wrap" Text="Salon Başkanı" TextAlignment="Center" Foreground="Black" FontFamily="Noto Sans" Style="{StaticResource BodyTextBlockStyle}" FontWeight="Bold" Grid.Row="1"/>
</Grid>
<Grid x:Name="InfoArea" HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Stretch" Grid.Row="2">
<Grid.RowDefinitions>
<RowDefinition Height="*"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="auto"></ColumnDefinition>
<ColumnDefinition Width="*"></ColumnDefinition>
</Grid.ColumnDefinitions>
<TextBlock x:Name="SpecsH_1" Margin="0,0,5,0" TextWrapping="Wrap" Text="Sınav Yeri / Exam Area: " Foreground="#FF343434" FontStyle="Italic" FontWeight="Bold" VerticalAlignment="Stretch" FontFamily="Noto Sans" Style="{StaticResource BodyTextBlockStyle}" TextAlignment="Left"/>
<TextBlock x:Name="SpecsH_2" Margin="0,0,5,0" TextWrapping="Wrap" Text="Salon Adı / Hall Name:" Foreground="#FF343434" FontStyle="Italic" FontWeight="Bold" VerticalAlignment="Stretch" FontFamily="Noto Sans" Style="{StaticResource BodyTextBlockStyle}" TextAlignment="Left" Grid.Row="1"/>
<TextBlock x:Name="SpecsH_3" Margin="0,0,5,0" TextWrapping="Wrap" Text="Salon No / Hall Number:" Foreground="#FF343434" FontStyle="Italic" FontWeight="Bold" VerticalAlignment="Stretch" FontFamily="Noto Sans" Style="{StaticResource BodyTextBlockStyle}" TextAlignment="Left" Grid.Row="2"/>
<TextBlock x:Name="AreaText" Margin="5,0,0,0" TextWrapping="Wrap" Text="İstanbul" Foreground="#FF343434" FontStyle="Italic" VerticalAlignment="Stretch" FontFamily="Noto Sans" Style="{StaticResource BodyTextBlockStyle}" Grid.Column="1"/>
<TextBlock x:Name="HallNameText" Margin="5,0,0,0" TextWrapping="Wrap" Text="A Blok 3. Kat Derslik 316" Foreground="#FF343434" FontStyle="Italic" VerticalAlignment="Stretch" FontFamily="Noto Sans" Style="{StaticResource BodyTextBlockStyle}" Grid.Row="1" Grid.Column="1"/>
<TextBlock x:Name="HallNoText" Margin="5,0,0,0" TextWrapping="Wrap" Text="340111" Foreground="#FF343434" FontStyle="Italic" VerticalAlignment="Stretch" FontFamily="Noto Sans" Style="{StaticResource BodyTextBlockStyle}" Grid.Row="2" Grid.Column="1"/>
</Grid>
<Grid x:Name="HeaderArea" HorizontalAlignment="Stretch" Margin="0,0,0,5" VerticalAlignment="Stretch">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
<RowDefinition Height="*"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="70"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="70"/>
</Grid.ColumnDefinitions>
<Image HorizontalAlignment="Stretch" Height="70" Margin="0,0,0,0" Grid.RowSpan="4" VerticalAlignment="Stretch" Width="70" Source="Assets/AUSmall.png"/>
<Image HorizontalAlignment="Stretch" Height="70" Margin="0,0,0,0" Grid.RowSpan="4" VerticalAlignment="Stretch" Width="70" Grid.Column="2" Source="Assets/AnkudemSmall.png"/>
<TextBlock x:Name="Header_1" Margin="0,0,0,0" TextWrapping="Wrap" Text="AYÖS" TextAlignment="Center" FontWeight="Bold" Foreground="#FF284985" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" Style="{StaticResource SubtitleTextBlockStyle}" FontFamily="Noto Sans" Grid.Column="1"/>
<TextBlock x:Name="Header_2" Margin="0,0,0,0" TextWrapping="Wrap" Text="SINAV GÖREV KARTI" TextAlignment="Center" Foreground="#FF284985" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Style="{StaticResource BodyTextBlockStyle}" FontFamily="Noto Sans" Grid.Row="1" Grid.Column="1"/>
<TextBlock x:Name="Header_3" Margin="0,0,0,0" TextWrapping="Wrap" Text="EXAMINATION TASK CARD" TextAlignment="Center" Foreground="#FF284985" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Style="{StaticResource BodyTextBlockStyle}" FontFamily="Noto Sans" Grid.Row="2" Grid.Column="1"/>
<TextBlock x:Name="DateText" Margin="0,0,0,0" TextWrapping="Wrap" TextAlignment="Center" Foreground="#FF284985" Text="28 Mayıs 2016 – May 28, 2016" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Style="{StaticResource BodyTextBlockStyle}" FontFamily="Noto Sans" RenderTransformOrigin="0.5,0.5" Grid.Row="3" Grid.Column="1">
<TextBlock.RenderTransform>
<CompositeTransform ScaleY="1"/>
</TextBlock.RenderTransform>
</TextBlock>
</Grid>
</Grid>
</Grid>
</Grid>
我是这样初始化的：
//Initializing task card.
var item = new TaskCard(Name_TextBox.Text.ToUpper() + " " + Surname_TextBox.Text.ToUpper(), Task_TextBox.Text, ExamArea_TextBox.Text, HallName_TextBox.Text, HallNumber_TextBox.Text, DateConverter.Get(Date_Picker.Date.ToString())); // Creating card.
之后，如您所知，我们必须在任何使用 renderTargetBitmap 的东西上显示 UserControl needed.So，我准备了一个网格来显示 UserControl。
<Grid x:Name="RingWaiter_Grid" BorderBrush="{ThemeResource SystemControlBackgroundBaseHighRevealBorderBrush}" Background="{ThemeResource ApplicationPageBackgroundThemeBrush}" RequestedTheme="Default" HorizontalAlignment="Center" VerticalAlignment="Center" BorderThickness="2,2,2,2" Margin="0,0,0,0" Visibility="Visible">
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
<RowDefinition Height="auto"/>
</Grid.RowDefinitions>
<Grid x:Name="RingWaiter_SecondRow" HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Stretch" Grid.Row="2" Visibility="Visible">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<TextBlock x:Name="LoadValue_Ring" Text="Lütfen bekleyin..." TextWrapping="Wrap" FontWeight="Normal" Margin="10,0,10,0" TextAlignment="Center" VerticalAlignment="Center" HorizontalAlignment="Stretch" Grid.Column="1" Style="{StaticResource SubtitleTextBlockStyle}" />
<ProgressRing x:Name="Waiter_Ring" HorizontalAlignment="Center" Margin="10,10,10,10" VerticalAlignment="Center" Foreground="{StaticResource AndroidGreen}" IsActive="True" Width="40" Height="40"/>
</Grid>
<Frame x:Name="ItemAddFrame_RingWaiter" HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Stretch" Width="486" Height="306"/>
</Grid>
//Converting UIelement to Rendered Bitmap
ItemAddFrame_RingWaiter.Content = item; // Adding card to canvas.
RenderTargetBitmap renderTargetBitmap = new RenderTargetBitmap();
await renderTargetBitmap.RenderAsync(ItemAddFrame_RingWaiter); // Render frame.
var pixelBuffer = await renderTargetBitmap.GetPixelsAsync();
最后，您可以在我的用户控件中看到两个图像元素。将它绑定到框架后看起来很完美。但是，当我使用 FileSavePicker 和 BitmapEncoder 将它导出到图像时，我的用户控件中的那些图像元素随机出现和消失。如果我尝试导出所有 WaiterGrid，图像控件将保留在其原始位置。我想不通。你可以帮帮我吗？谢谢。
网格上的用户控件：
导出的图像
However, when I exported it to a image with FileSavePicker and BitmapEncoder, those Image elements in my user controls randomly appear and disappeared
这是由于没有足够的时间加载图像造成的。只要将 UserControl taskcard 添加到框架中，就会立即呈现框架。但是在那段时间渲染 ItemAddFrame_RingWaiter 时图像未加载完成，因此不会渲染图像。添加Task.Delay等待一段时间你会发现它很好用。
ItemAddFrame_RingWaiter.Content = item; // Adding card to canvas.
await Task.Delay(1000);
RenderTargetBitmap renderTargetBitmap = new RenderTargetBitmap();
await renderTargetBitmap.RenderAsync(ItemAddFrame_RingWaiter); // Render frame.
imgshow.Source = renderTargetBitmap;
Task.Delay 可以帮助了解原因，但不是一个好的解决方案。在您之前的帖子中，您可以看到在我的回答中，我通过如下代码在 XAML 中添加了 UserControl：
<local:taskcard
x:Name="elementToRender"
Width="300"
Height="350" />
如果通过这种方式添加UserControl，可能不会出现上述问题。我不确定你为什么要在后面添加控制代码，如果你确实想在后面添加控制代码，请尝试从你的 UserControl 里面监视 Image_Loaded 事件句柄。
我有一个这样的用户控件：
<UserControl x:Name="taskcard"
x:Class="AYOS_IDPrinter_UWP.TaskCard"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:AYOS_IDPrinter_UWP"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
HorizontalAlignment="Stretch" VerticalAlignment="Stretch" RequestedTheme="Default" Width="486" Height="306">
<UserControl.Resources>
<SolidColorBrush x:Key="AuSupportColor" Color="#FFE5C97C"/>
</UserControl.Resources>
<Grid x:Name="MainGrid" Background="White" Margin="0,0,0,0" RequestedTheme="Default">
<Grid x:Name="Skeleton" Margin="10,10,10,10" BorderThickness="2,2,2,2" BorderBrush="{StaticResource AuSupportColor}">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid x:Name="NeedleArea" BorderThickness="0,0,0,2" BorderBrush="{StaticResource AuSupportColor}" Background="{StaticResource AUColor}" Margin="0,0,0,0">
<TextBlock x:Name="Label" TextWrapping="Wrap" Text="İğne Alanı / Needle Area" Foreground="White" TextAlignment="Center" VerticalAlignment="Center" FontFamily="Noto Sans" FontWeight="Normal" Style="{StaticResource CaptionTextBlockStyle}" Margin="0,4,0,5"/>
</Grid>
<Grid x:Name="Datas" HorizontalAlignment="Stretch" Margin="10,10,10,10" VerticalAlignment="Stretch" Grid.Row="1">
<Grid.RowDefinitions>
<RowDefinition Height="*"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
</Grid.RowDefinitions>
<Grid x:Name="Name_Task_Area" HorizontalAlignment="Stretch" Margin="0,5,0,5" VerticalAlignment="Stretch" Grid.Row="1">
<Grid.RowDefinitions>
<RowDefinition Height="*"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
</Grid.RowDefinitions>
<TextBlock x:Name="NameText" Margin="0,0,0,0" TextWrapping="Wrap" TextAlignment="Center" Foreground="Red" Text="BERK BABADOĞAN" FontWeight="Bold" FontFamily="Noto Sans" Style="{StaticResource SubtitleTextBlockStyle}"/>
<TextBlock x:Name="TaskText" Margin="0,0,0,0" TextWrapping="Wrap" Text="Salon Başkanı" TextAlignment="Center" Foreground="Black" FontFamily="Noto Sans" Style="{StaticResource BodyTextBlockStyle}" FontWeight="Bold" Grid.Row="1"/>
</Grid>
<Grid x:Name="InfoArea" HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Stretch" Grid.Row="2">
<Grid.RowDefinitions>
<RowDefinition Height="*"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="auto"></ColumnDefinition>
<ColumnDefinition Width="*"></ColumnDefinition>
</Grid.ColumnDefinitions>
<TextBlock x:Name="SpecsH_1" Margin="0,0,5,0" TextWrapping="Wrap" Text="Sınav Yeri / Exam Area: " Foreground="#FF343434" FontStyle="Italic" FontWeight="Bold" VerticalAlignment="Stretch" FontFamily="Noto Sans" Style="{StaticResource BodyTextBlockStyle}" TextAlignment="Left"/>
<TextBlock x:Name="SpecsH_2" Margin="0,0,5,0" TextWrapping="Wrap" Text="Salon Adı / Hall Name:" Foreground="#FF343434" FontStyle="Italic" FontWeight="Bold" VerticalAlignment="Stretch" FontFamily="Noto Sans" Style="{StaticResource BodyTextBlockStyle}" TextAlignment="Left" Grid.Row="1"/>
<TextBlock x:Name="SpecsH_3" Margin="0,0,5,0" TextWrapping="Wrap" Text="Salon No / Hall Number:" Foreground="#FF343434" FontStyle="Italic" FontWeight="Bold" VerticalAlignment="Stretch" FontFamily="Noto Sans" Style="{StaticResource BodyTextBlockStyle}" TextAlignment="Left" Grid.Row="2"/>
<TextBlock x:Name="AreaText" Margin="5,0,0,0" TextWrapping="Wrap" Text="İstanbul" Foreground="#FF343434" FontStyle="Italic" VerticalAlignment="Stretch" FontFamily="Noto Sans" Style="{StaticResource BodyTextBlockStyle}" Grid.Column="1"/>
<TextBlock x:Name="HallNameText" Margin="5,0,0,0" TextWrapping="Wrap" Text="A Blok 3. Kat Derslik 316" Foreground="#FF343434" FontStyle="Italic" VerticalAlignment="Stretch" FontFamily="Noto Sans" Style="{StaticResource BodyTextBlockStyle}" Grid.Row="1" Grid.Column="1"/>
<TextBlock x:Name="HallNoText" Margin="5,0,0,0" TextWrapping="Wrap" Text="340111" Foreground="#FF343434" FontStyle="Italic" VerticalAlignment="Stretch" FontFamily="Noto Sans" Style="{StaticResource BodyTextBlockStyle}" Grid.Row="2" Grid.Column="1"/>
</Grid>
<Grid x:Name="HeaderArea" HorizontalAlignment="Stretch" Margin="0,0,0,5" VerticalAlignment="Stretch">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
<RowDefinition Height="*"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="70"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="70"/>
</Grid.ColumnDefinitions>
<Image HorizontalAlignment="Stretch" Height="70" Margin="0,0,0,0" Grid.RowSpan="4" VerticalAlignment="Stretch" Width="70" Source="Assets/AUSmall.png"/>
<Image HorizontalAlignment="Stretch" Height="70" Margin="0,0,0,0" Grid.RowSpan="4" VerticalAlignment="Stretch" Width="70" Grid.Column="2" Source="Assets/AnkudemSmall.png"/>
<TextBlock x:Name="Header_1" Margin="0,0,0,0" TextWrapping="Wrap" Text="AYÖS" TextAlignment="Center" FontWeight="Bold" Foreground="#FF284985" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" Style="{StaticResource SubtitleTextBlockStyle}" FontFamily="Noto Sans" Grid.Column="1"/>
<TextBlock x:Name="Header_2" Margin="0,0,0,0" TextWrapping="Wrap" Text="SINAV GÖREV KARTI" TextAlignment="Center" Foreground="#FF284985" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Style="{StaticResource BodyTextBlockStyle}" FontFamily="Noto Sans" Grid.Row="1" Grid.Column="1"/>
<TextBlock x:Name="Header_3" Margin="0,0,0,0" TextWrapping="Wrap" Text="EXAMINATION TASK CARD" TextAlignment="Center" Foreground="#FF284985" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Style="{StaticResource BodyTextBlockStyle}" FontFamily="Noto Sans" Grid.Row="2" Grid.Column="1"/>
<TextBlock x:Name="DateText" Margin="0,0,0,0" TextWrapping="Wrap" TextAlignment="Center" Foreground="#FF284985" Text="28 Mayıs 2016 – May 28, 2016" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Style="{StaticResource BodyTextBlockStyle}" FontFamily="Noto Sans" RenderTransformOrigin="0.5,0.5" Grid.Row="3" Grid.Column="1">
<TextBlock.RenderTransform>
<CompositeTransform ScaleY="1"/>
</TextBlock.RenderTransform>
</TextBlock>
</Grid>
</Grid>
</Grid>
</Grid>
我是这样初始化的：
//Initializing task card.
var item = new TaskCard(Name_TextBox.Text.ToUpper() + " " + Surname_TextBox.Text.ToUpper(), Task_TextBox.Text, ExamArea_TextBox.Text, HallName_TextBox.Text, HallNumber_TextBox.Text, DateConverter.Get(Date_Picker.Date.ToString())); // Creating card.
之后，如您所知，我们必须在任何使用 renderTargetBitmap 的东西上显示 UserControl needed.So，我准备了一个网格来显示 UserControl。
<Grid x:Name="RingWaiter_Grid" BorderBrush="{ThemeResource SystemControlBackgroundBaseHighRevealBorderBrush}" Background="{ThemeResource ApplicationPageBackgroundThemeBrush}" RequestedTheme="Default" HorizontalAlignment="Center" VerticalAlignment="Center" BorderThickness="2,2,2,2" Margin="0,0,0,0" Visibility="Visible">
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
<RowDefinition Height="auto"/>
</Grid.RowDefinitions>
<Grid x:Name="RingWaiter_SecondRow" HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Stretch" Grid.Row="2" Visibility="Visible">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<TextBlock x:Name="LoadValue_Ring" Text="Lütfen bekleyin..." TextWrapping="Wrap" FontWeight="Normal" Margin="10,0,10,0" TextAlignment="Center" VerticalAlignment="Center" HorizontalAlignment="Stretch" Grid.Column="1" Style="{StaticResource SubtitleTextBlockStyle}" />
<ProgressRing x:Name="Waiter_Ring" HorizontalAlignment="Center" Margin="10,10,10,10" VerticalAlignment="Center" Foreground="{StaticResource AndroidGreen}" IsActive="True" Width="40" Height="40"/>
</Grid>
<Frame x:Name="ItemAddFrame_RingWaiter" HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Stretch" Width="486" Height="306"/>
</Grid>
//Converting UIelement to Rendered Bitmap
ItemAddFrame_RingWaiter.Content = item; // Adding card to canvas.
RenderTargetBitmap renderTargetBitmap = new RenderTargetBitmap();
await renderTargetBitmap.RenderAsync(ItemAddFrame_RingWaiter); // Render frame.
var pixelBuffer = await renderTargetBitmap.GetPixelsAsync();
最后，您可以在我的用户控件中看到两个图像元素。将它绑定到框架后看起来很完美。但是，当我使用 FileSavePicker 和 BitmapEncoder 将它导出到图像时，我的用户控件中的那些图像元素随机出现和消失。如果我尝试导出所有 WaiterGrid，图像控件将保留在其原始位置。我想不通。你可以帮帮我吗？谢谢。
网格上的用户控件：
导出的图像
However, when I exported it to a image with FileSavePicker and BitmapEncoder, those Image elements in my user controls randomly appear and disappeared
这是由于没有足够的时间加载图像造成的。只要将 UserControl taskcard 添加到框架中，就会立即呈现框架。但是在那段时间渲染 ItemAddFrame_RingWaiter 时图像未加载完成，因此不会渲染图像。添加Task.Delay等待一段时间你会发现它很好用。
ItemAddFrame_RingWaiter.Content = item; // Adding card to canvas.
await Task.Delay(1000);
RenderTargetBitmap renderTargetBitmap = new RenderTargetBitmap();
await renderTargetBitmap.RenderAsync(ItemAddFrame_RingWaiter); // Render frame.
imgshow.Source = renderTargetBitmap;
Task.Delay 可以帮助了解原因，但不是一个好的解决方案。在您之前的帖子中，您可以看到在我的回答中，我通过如下代码在 XAML 中添加了 UserControl：
<local:taskcard
x:Name="elementToRender"
Width="300"
Height="350" />
如果通过这种方式添加UserControl，可能不会出现上述问题。我不确定你为什么要在后面添加控制代码，如果你确实想在后面添加控制代码，请尝试从你的 UserControl 里面监视 Image_Loaded 事件句柄。