DataTemplate找不到类型，因为未知的命名空间Xamarin.Forms UWP

Question

I'm working with Xamarin.Forms and I was trying to make a Custom Renderer for TabbedPage (UWP) and it kind of works... But when I try to create a new DataTemplate in C# referencing another Custom Renderer I get an error and I can't find any solution to that.

Windows.UI.Xaml.DataTemplate GetStyledHeaderTemplate() {
    StringBuilder tpl = new StringBuilder();
    tpl.Append("<DataTemplate xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\"");
    tpl.Append(" xmlns:tint=\"clr-namespace:MyNamespace.UI;assembly=MyNamespace\"");
    tpl.Append(" xmlns:x=\"http://schemas.microsoft.com/winfx/2006/xaml\">");
    tpl.Append("<StackPanel Margin=\"0\" Padding=\"5, 0\" VerticalAlignment=\"Top\">");
    tpl.Append("<tint:ImageTinted TintColor=\"White\" Source=\"{Binding UWPIcon}\" Width=\"24\" Height=\"24\" Margin=\"0, 5, 0, 0\" />");
    tpl.Append("<TextBlock Padding=\"0\" Margin=\"0, 0, 0, 4\"");
    tpl.Append(" Text=\"{Binding Title}\" FontFamily=\"Segoe UI\" Foreground=\"White\" HorizontalAlignment=\"Center\" FontSize=\"13\" />");
    tpl.Append("</StackPanel>");
    tpl.Append("</DataTemplate>");
    return (Windows.UI.Xaml.DataTemplate)XamlReader.Load(tpl.ToString());
}

The code works fine when I don't call

<tint:ImageTinted />

from the DataTemplate and ImageTinted works in other places.

Please, help!

Error:

Windows.UI.Xaml.Markup.XamlParseException occurred
  HResult=0x802B000A
  Message=The text associated with this error code could not be found.

The type 'ImageTinted' was not found because 'clr-namespace:MyNamespace.UI;assembly=MyNamespace' is an unknown namespace. [Line: 1 Position: 339]
  Source=
  StackTrace:
   at Windows.UI.Xaml.Markup.XamlReader.Load(String xaml)
   at MyNamespace.UWP.StyledTabbedPageRenderer.GetStyledHeaderTemplate() in D:\...\MyNamespace.UWP\UI\Renderers\StyledTabbedPageRenderer.cs:line 91
   at MyNamespace.UWP.StyledTabbedPageRenderer.OnElementChanged(VisualElementChangedEventArgs e) in D:\...\MyNamespace.UWP\UI\Renderers\StyledTabbedPageRenderer.cs:line 35
   at Xamarin.Forms.Platform.UWP.TabbedPageRenderer.SetElement(VisualElement element)
   at Xamarin.Forms.Platform.UWP.Platform.CreateRenderer(VisualElement element)
   at Xamarin.Forms.Platform.UWP.VisualElementExtensions.GetOrCreateRenderer(VisualElement self)
   at Xamarin.Forms.Platform.UWP.Platform.<SetCurrent>d__51.MoveNext()

Answer 1

tpl.Append(" xmlns:tint=\"clr-namespace:MyNamespace.UI;assembly=MyNamespace\"");

将MyNamespace.UI更改为名称空间程序集的名称应为程序集的名称（在这种情况下，您的PCL项目的名称

Answer 2

In the UWP project containing your renderer, assuming MyNamespace.UI is the namespace of class ImageTinted and the assembly is referenced, replace this

tpl.Append(" xmlns:tint=\"clr-namespace:MyNamespace.UI;assembly=MyNamespace\"");

with the following:

tpl.Append(" xmlns:tint=\"using:MyNamespace.UI\"");

For example, if ImageTinted in the UWP project look like this:

<UserControl
x:Class="MyNamespace.UI.ImageTinted"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">

<TextBlock Text="ImageTinted"/>

This should load the template in the XamlReader.Load statement.

Debug by setting a breakpoint at the end brace of GetStyledHeaderTemplate() , ie after the return statement. No exceptions from XamlReader.Load should be observed at this point.

If you still have errors then you should look into the ImageTinted class.

Here is an example UWP Renderer for TabbedPage:

[assembly: ExportRenderer(typeof(TabbedPage), typeof(MyTabbedPageRenderer))]
namespace MyRenderer.UWP
{
  public class MyTabbedPageRenderer : TabbedPageRenderer
  {
    protected override void OnElementChanged(VisualElementChangedEventArgs e)
    {
        base.OnElementChanged(e);

        if (Control != null)
        {
            Control.HeaderTemplate = GetStyledHeaderTemplate();
        }
    }
  }

  private Windows.UI.Xaml.DataTemplate GetStyledHeaderTemplate()
  {
    string xaml = @"
<DataTemplate 
    xmlns=""http://schemas.microsoft.com/winfx/2006/xaml/presentation""
    xmlns:x=""http://schemas.microsoft.com/winfx/2006/xaml""
    xmlns:tint=""using:MyNamespace.UI"">
<StackPanel Orientation=""Horizontal"">
    <tint:ImageTinted Source=""{Binding Icon}""/>
    <TextBlock Text=""{Binding Title}"" FontFamily=""Segoe UI"" 
FontSize=""13"" />
</StackPanel>
</DataTemplate>";

    return (Windows.UI.Xaml.DataTemplate)XamlReader.Load(xaml);
  }
}