我有一个 WPF 应用程序,在 UI 线程上有一个长时间运行的任务,我想为其显示进度条 (*)。由于 UI 很忙,按照 this 解决方案,我选择在单独的 UI/STA 线程上打开带有进度条的窗口。
一切正常 - 我第一次创建窗口时。问题显然是窗口使用
Style="{StaticResource CustomWindowStyle}"
并且样式的实例是静态的,即“缓存”并在使用此样式的所有实例之间共享。
但是,这个实例(作为所有/大多数 UI 元素)是一个
DispatcherObject
,只能在最初创建它的线程中使用。因此,当我第二次打开一个窗口(在它自己的新 UI 线程上)时,它会访问之前在不同线程上构建的相同静态 Style
资源,并且出现以下异常:
System.Windows.Markup.XamlParseException
HResult=0x80131501
Message='Set property 'System.Windows.FrameworkElement.Style' threw an exception.' Line number '15' and line position '9'.
Source=PresentationFramework
StackTrace:
at System.Windows.Markup.XamlReader.RewrapException(Exception e, IXamlLineInfo lineInfo, Uri baseUri)
This exception was originally thrown at this call stack:
System.Windows.StyleHelper.ProcessInstanceValuesHelper(ref MS.Utility.ItemStructList<System.Windows.ChildValueLookup>, System.Windows.DependencyObject, int, System.Collections.Specialized.HybridDictionary, bool)
System.Windows.StyleHelper.ProcessInstanceValuesForChild(System.Windows.DependencyObject, System.Windows.DependencyObject, int, System.Collections.Specialized.HybridDictionary, bool, ref MS.Utility.FrugalStructList<System.Windows.ChildRecord>)
System.Windows.StyleHelper.DoStyleInvalidations(System.Windows.FrameworkElement, System.Windows.FrameworkContentElement, System.Windows.Style, System.Windows.Style)
System.Windows.StyleHelper.UpdateStyleCache(System.Windows.FrameworkElement, System.Windows.FrameworkContentElement, System.Windows.Style, System.Windows.Style, ref System.Windows.Style)
System.Windows.FrameworkElement.OnStyleChanged(System.Windows.DependencyObject, System.Windows.DependencyPropertyChangedEventArgs)
System.Windows.DependencyObject.OnPropertyChanged(System.Windows.DependencyPropertyChangedEventArgs)
System.Windows.FrameworkElement.OnPropertyChanged(System.Windows.DependencyPropertyChangedEventArgs)
System.Windows.DependencyObject.NotifyPropertyChange(System.Windows.DependencyPropertyChangedEventArgs)
System.Windows.DependencyObject.UpdateEffectiveValue(System.Windows.EntryIndex, System.Windows.DependencyProperty, System.Windows.PropertyMetadata, System.Windows.EffectiveValueEntry, ref System.Windows.EffectiveValueEntry, bool, bool, System.Windows.OperationType)
System.Windows.DependencyObject.SetValueCommon(System.Windows.DependencyProperty, object, System.Windows.PropertyMetadata, bool, bool, System.Windows.OperationType, bool)
...
[Call Stack Truncated]
Inner Exception 1:
InvalidOperationException: Cannot access Freezable 'System.Windows.Shell.WindowChrome' across threads because it cannot be frozen.
如果我删除
Style
属性,一切都很好。
我也尝试使用
DynamicResource
,但引用的样式引用了我无法控制的其他静态资源,并导致“进一步”出现相同的问题。
这个问题可以解决吗?
(*) 是的,我知道:长时间运行的操作不应由 UI 线程处理,但更改这一点将需要太多重构(目前),并且即使发生这种情况,用户也不会执行任何操作,如果该操作被外包给一个任务,无论如何我实际上都会禁用 UI。
编辑1:所以引导我到这篇文章;我尝试将
x:Shared="False"
添加到窗口声明中,但没有帮助。
编辑2:我还尝试按照here所述冻结样式资源,但没有帮助。
如here所述,解决方案是为引用的样式设置
x:Shared="True"
- 而不是窗口。
幸运的是,就我而言,我确实可以控制此样式定义(但不能控制该样式使用的其他资源),因此我可以修改它的定义。
由于我非常希望不必修改样式,因此我还尝试在
Window.Resources
中定义本地样式,如下所示:
<Window.Resources>
<Style x:Key="CustomStyle" TargetType="{x:Type Window}" BasedOn="{StaticResource CustomWindowStyle}" x:Shared="False"/>
</Window.Resources>
然后我尝试用它来代替。首先,我必须通过代码分配样式,因为我无法弄清楚如何在窗口属性中使用样式,该属性(稍后)定义为窗口自己的资源之一:
this.Style = this.Resources["CustomStyle"] as Style;
但是,遗憾的是,由于以下异常(仅在那一行)而失败:
System.InvalidOperationException
HResult=0x80131509
Message=The calling thread cannot access this object because a different thread owns it.
Source=WindowsBase
StackTrace:
at System.Windows.Threading.Dispatcher.VerifyAccess()
at System.Windows.Freezable.System.Windows.ISealable.get_IsSealed()
at System.Windows.StyleHelper.SealIfSealable(Object value)
at System.Windows.Setter.Seal()
at System.Windows.SetterBaseCollection.Seal()
at System.Windows.Style.ProcessSetters(Style style)
at System.Windows.Style.ProcessSetters(Style style)
at System.Windows.Style.Seal()
at System.Windows.StyleHelper.UpdateStyleCache(FrameworkElement fe, FrameworkContentElement fce, Style oldStyle, Style newStyle, Style& styleCache)
at System.Windows.FrameworkElement.OnStyleChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
at System.Windows.DependencyObject.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
at System.Windows.FrameworkElement.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
at System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args)
at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType)
at System.Windows.DependencyObject.SetValueCommon(DependencyProperty dp, Object value, PropertyMetadata metadata, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType, Boolean isInternal)
at System.Windows.DependencyObject.SetValue(DependencyProperty dp, Object value)
at ...PopupWindow..ctor()...
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
This exception was originally thrown at this call stack:
System.Windows.Threading.Dispatcher.VerifyAccess()
System.Windows.Freezable.System.Windows.ISealable.IsSealed.get()
System.Windows.StyleHelper.SealIfSealable(object)
System.Windows.Setter.Seal()
System.Windows.SetterBaseCollection.Seal()
System.Windows.Style.ProcessSetters(System.Windows.Style)
System.Windows.Style.ProcessSetters(System.Windows.Style)
System.Windows.Style.Seal()
System.Windows.StyleHelper.UpdateStyleCache(System.Windows.FrameworkElement, System.Windows.FrameworkContentElement, System.Windows.Style, System.Windows.Style, ref System.Windows.Style)
System.Windows.FrameworkElement.OnStyleChanged(System.Windows.DependencyObject, System.Windows.DependencyPropertyChangedEventArgs)
...
[Call Stack Truncated]
所以,现在我使用修改后的静态样式:
<Style x:Key="CustomWindowStyle" TargetType="{x:Type Window}" x:Shared="False">
...
</Style>