XAML绑定BitmapImage ViewModel属性 [英] XAML bind BitmapImage ViewModel property
问题描述
我对视图模型类的更新列表框有疑问.我使用Caliburn Micro框架.我的情况是在这里:
I have problem with update listbox from view model class. I use Caliburn Micro framework. My scenario is here:
我在列表框上绑定了bindableCollection类型的属性:
I bind property of type bindableCollection on listbox:
视图模型中的代码:
private BindableCollection<UserInfo> _friends;
public BindableCollection<UserInfo> Friends
{
get { return _friends; }
set
{
_friends= value;
NotifyOfPropertyChange(()=>Friends);
}
}
在视图模型中，我创建了伪造的服务方法，将新的新数据作为列表返回，并使用此数据更新了在列表框上绑定的属性Friends.
In view model I create fake service method wich return new fresh data as List and with this data I update property Friends which is bind on listbox.
我每3秒在调度程序计时器滴答事件中调用一次伪造的服务方法.
I call fake service method in dispatcher timer tick event every 3 seconds.
private static UserInfo FakeUser()
{
var user = new UserInfo
{
Age = "16",
Emphasis = true,
IdUser = "11542",
IsBlocked = false,
IsFriend = true,
LocationInfo = new Location
{
CityName = "TN",
IdCity = 123456,
IdRegion = 1246,
RegionName = "TN",
},
StatusInfo = new Status
{
IdChat = 12,
IsLogged = true,
LastLogin = "153151",
IsChating = true,
RoomName = "Car",
},
ProjectStatusInfo = new ProjectStatus(),
IsIamFriend = true,
PlusInfo = new Plus(),
ProfilePhoto = new BitmapImage(new Uri("http://pokec.azet.sk/vanes90?i9=1f104a294997", UriKind.RelativeOrAbsolute))
};
return user;
}
private static IEnumerable<UserInfo> GetFakeFriends()
{
var list = new List<UserInfo>();
for (int i = 0; i < 20; i++)
{
list.Add(FakeUser());
}
return list;
}
private void DispatcherTimer_Tick(object sender, EventArgs eventArgs)
{
if (_isExecuting)
return;
_isExecuting = true;
new System.Threading.Tasks.Task(() =>
{
var freshFriends = GetFakeFriends();
Execute.OnUIThread((System.Action)(() =>
{
Friends.Clear();
foreach (var freshFriend in freshFriends)
{
Friends.Add(freshFriend);
}
}));
}).Start();
_isExecuting = false;
}
}
如果我不在列表框上应用任何样式，则效果很好.
If I don’t apply any style on listbox, it works good.
查看:
<Grid>
<ListBox Name="Friends"
Grid.Row="2"
Margin="4,4,4,4">
</ListBox>
</Grid>
如果我应用某种样式来绑定列表框上UserInfo的属性ProfilePhoto(BitmapeImage的类型).
If I apply some style in which I bind property ProfilePhoto (typeof BitmapeImage) from UserInfo on listbox.
样式在这里:
<Style x:Key="friendsListStyle" TargetType="{x:Type ListBox}">
<Setter Property="ItemTemplate">
<Setter.Value>
<DataTemplate>
<Grid Name="RootLayout">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="0.3*"></ColumnDefinition>
<ColumnDefinition Width="*"></ColumnDefinition>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="60"></RowDefinition>
</Grid.RowDefinitions>
<Image Margin="4,4,4,2" Source="{Binding Path=ProfilePhoto}" Grid.Column="0"/>
</Grid>
</DataTemplate>
</Setter.Value>
</Setter>
</Style>
我收到此错误:
Must create DependencySource on same Thread as the DependencyObject.
at System.Windows.Markup.XamlReader.RewrapException(Exception e, Uri baseUri)
at System.Windows.FrameworkTemplate.LoadTemplateXaml(XamlReader templateReader, XamlObjectWriter currentWriter)
at System.Windows.FrameworkTemplate.LoadTemplateXaml(XamlObjectWriter objectWriter)
at System.Windows.FrameworkTemplate.LoadOptimizedTemplateContent(DependencyObject container, IComponentConnector componentConnector, IStyleConnector styleConnector, List`1 affectedChildren, UncommonField`1 templatedNonFeChildrenField)
at System.Windows.FrameworkTemplate.LoadContent(DependencyObject container, List`1 affectedChildren)
at System.Windows.StyleHelper.ApplyTemplateContent(UncommonField`1 dataField, DependencyObject container, FrameworkElementFactory templateRoot, Int32 lastChildIndex, HybridDictionary childIndexFromChildID, FrameworkTemplate frameworkTemplate)
at System.Windows.FrameworkTemplate.ApplyTemplateContent(UncommonField`1 templateDataField, FrameworkElement container)
at System.Windows.FrameworkElement.ApplyTemplate()
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Controls.Border.MeasureOverride(Size constraint)
如果我在列表框/列表框项目上创建其他样式，则在仅绑定字符串或bool属性的情况下，效果很好.
If I make another style on listbox / listbox item, in wich I bind only string or bool properties it works good.
仅当绑定bitmapImage属性时，我才有问题.
I have problem only if bind bitmapImage property.
BitmapImage属性的初始化方式为:
BitmapImage property is init as:
ProfilePhoto = new BitmapImage(new Uri("http://pokec.azet.sk/vanes90?i9=1f104a294997", UriKind.RelativeOrAbsolute))
URI是图片的URL或文件的路径.
URI is url of picture or path to the file.
怎么了?感谢您的帮助和建议.
What is wrong? Thank for help and advice.
样式很好，只有当我不使用另一个线程中的方法调用刷新数据时，它才起作用.
Style is good, it work only if I don’t refresh data with method call in another thread.
推荐答案
如果要在UI线程以外的任何线程上创建BitmapImage，则可以解释此问题.您可以冻结BitmapImage以确保可以从任何线程对其进行访问:
If you're creating the BitmapImage on any thread other than the UI thread, that would explain this issue. You can freeze the BitmapImage to ensure it is accessible from any thread:
var bitmapImage = new BitmapImage(...);
bitmapImage.Freeze();
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