当我调整窗口大小时，带有数据选择器的UWP Treeview在App.g.cs中生成错误 [英] UWP Treeview with Data selector generating an error in App.g.cs when I resize the window
问题描述
团队，这是很奇怪的事情，我不知道如何调试它.我有树视图.在树状视图中，我有2种类型:顾客访问
Team, this is something very strange and I do not understand how to debug it. I have a tree view. Within the tree view I have 2 types: Customer Visit
所有根元素都是客户所有子元素都是访问次数"
ALL root elements are Customers ALL child elements are Visits
我已经完成了一些选择器，以显示正确的关卡图标:
I've done some selectors to show the correct icons for the level:
现在，如果列表不超过树视图的末尾，则当我打开叶子时，它将起作用:
Now when I open the leafs IF the list does NOT exceed the end of the tree view it works:
但是，如果我打开了超出窗口一侧的叶子:
But if I open a leaf that EXCEEDS the window side:
我收到此错误:
发件人:应用程序例外: {指定的类型转换无效."}
Sender: the App
Exception:
{"Specified cast is not valid."}
消息:
"System.InvalidCastException: Unable to cast object of type 'TitoDoc2020.Models.MTreeViewVisit' to type 'TitoDoc2020.Models.MTreeViewPaz'.\r\n at TitoDoc2020.Views.TitoDocPage.TitoDocPage_obj107_Bindings.SetDataRoot(Object newDataRoot)\r\n at TitoDoc2020.Views.TitoDocPage.TitoDocPage_obj107_Bindings.ProcessBindings(Object item, Int32 itemIndex, Int32 phase, Int32& nextPhase)"
但我不打算这么做！我真的不知道它可能发生在哪里.
BUT I'm NOT casting that! I really do not understand where it could happen.
完整的项目在此处可见.
推荐答案
根据错误消息的描述，其原因在于绑定的类型转换，与它是否超出绑定无关.窗户.
According to the description of the error message, the reason for this is on the type conversion of the binding and has nothing to do with whether it is out of the window.
请检查您的绑定数据，以查看是否将 MTreeViewVisit 绑定到 MTreeViewPaz .
Please check your binding data to see if you have incorrectly bound MTreeViewVisit to MTreeViewPaz.
更新
最初的猜测可能是窗口的调整导致了可见区域的变化，进而导致了某些 TreeView 条目加载问题.
The initial speculation may be that the adjustment of the window caused the change in the visible area, which in turn caused some TreeView entry loading problems.
我注意到，在项目中，每次加载数据时都会创建一个 TitoDocContext ，这是不推荐的.
I noticed that in the project you will create a TitoDocContext whenever it comes to loading data, which is not recommended.
您应该只创建一个 TitoDocContext ，并在需要的地方传递引用，而不是使用 using 语句来释放上下文.因为频繁创建 DbContext 将带来巨大的资源开销，所以这也可能与您的 TreeView 条目加载异常有关.实际上，我创建了一个包含1000个条目的列表，并且在删除SqlServer之后，它运行良好.
You should only create a TitoDocContext, and pass the reference where it is needed, not use the using statement to release the Context. Because the frequent creation of DbContext will bring huge resource overhead, this may also be related to your TreeView entry loading exception. In fact, I created a List with 1000 entries and after getting rid of SqlServer, it worked well.
更新
我转载了您的问题.从实际问题的角度来看，这应归因于 TreeView 中条目的重用.为了减少系统资源的开销， TreeView (包括 ListView 和 GridView )将重用以前呈现的模板.因为您使用了 ItemTemplateSelector ，所以实际的数据类型和重用的模板不一致，从而导致错误.
I reproduced your question. From the point of view of the actual problem, it should be due to the reuse of entries within the TreeView. In order to reduce the overhead of system resources, TreeView (including ListView and GridView) will reuse previously rendered templates. Because you used ItemTemplateSelector, the actual data type and the reused template are inconsistent, causing an error.
我的建议是创建一个 UserControl 来替换 ItemTemplateSelector .
My suggestion is to create a UserControl to replace ItemTemplateSelector.
1.提取Visits集合并创建基类
public class MTreeViewBase
{
public ObservableCollection<MTreeViewVisit> Visits { get; } = new ObservableCollection<MTreeViewVisit>();
}
public class MTreeViewVisit : MTreeViewBase { }
public class MTreeViewPaz : MTreeViewBase { }
2.创建一个UserControl
TestControl.xaml
<UserControl.Resources>
<DataTemplate x:Name="PAZTemplate" x:DataType="model:MTreeViewPaz">
<StackPanel Orientation="Horizontal">
<FontIcon
Margin="{StaticResource XXSmallTopRightBottomMargin}"
FontFamily="{StaticResource SymbolThemeFontFamily}"
Glyph="" />
<TextBlock
Margin="{StaticResource XXSmallTopRightBottomMargin}"
VerticalAlignment="Center"
Text="{x:Bind Name}" />
</StackPanel>
</DataTemplate>
<DataTemplate x:Name="VisitTemplate" x:DataType="model:MTreeViewVisit">
<StackPanel Orientation="Horizontal">
<FontIcon
Margin="{StaticResource XXSmallTopRightBottomMargin}"
FontFamily="{StaticResource SymbolThemeFontFamily}"
Foreground="{x:Bind ImageColor}"
Glyph="{x:Bind ImageSrc}" />
<TextBlock
Margin="{StaticResource XXSmallTopRightBottomMargin}"
VerticalAlignment="Center"
Text="{x:Bind VisitDescr}" />
</StackPanel>
</DataTemplate>
</UserControl.Resources>
<Grid>
<ContentControl x:Name="MainContent"/>
</Grid>
3.创建用于内部转化的相关属性
TestControl.xaml.cs
public MTreeViewBase Data
{
get { return (MTreeViewBase)GetValue(DataProperty); }
set { SetValue(DataProperty, value); }
}
// Using a DependencyProperty as the backing store for Data. This enables animation, styling, binding, etc...
public static readonly DependencyProperty DataProperty =
DependencyProperty.Register("Data", typeof(MTreeViewBase), typeof(TestControl), new PropertyMetadata(null,new PropertyChangedCallback(Data_Changed)));
private static void Data_Changed(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
if (e.NewValue != null)
{
var instance = d as TestControl;
if(e.NewValue is MTreeViewPaz)
{
instance.MainContent.ContentTemplate = instance.PAZTemplate;
}
else
{
instance.MainContent.ContentTemplate = instance.VisitTemplate;
}
}
}
4.修改您的TreeView和ItemTemplate
<DataTemplate x:Key="BaseTemplate" x:DataType="model:MTreeViewBase">
<winui:TreeViewItem
IsExpanded="False"
ItemsSource="{x:Bind Visits}">
<controls1:TestControl Data="{Binding}"/>
</winui:TreeViewItem>
</DataTemplate>
<winui:TreeView
...
ItemTemplate="{StaticResource BaseTemplate}"
... />
这可以确保两种类型的入口相同，并且转换是在内部完成的，从而可以有效地解决此问题.
This can ensure that the two types have the same entrance, and the conversion is done internally, which can effectively solve this problem.
谢谢.
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