以下是我View
的一部分,其中我已将图片绑定到ViewModel
中的属性:
<Image Source="{Binding Image}" Grid.Column="2" Grid.ColumnSpan="2"/>
我的ViewModel
就是这样:
public class MainWindowViewModel : INotifyPropertyChanged
{
public BitmapImage Image
{
get { return _image; }
set
{
_image = value;
OnPropertyChanged();
}
}
Action _makeScannerAlwaysOnAction;
private BitmapImage _image;
public MainWindowViewModel()
{
AddNewPersonCommand = new RelayCommand(OpenFrmAddNewPerson);
FingerPrintScannerDevice.FingerPrintScanner.Init();
MakeScannerAlwaysOn(null);
}
private void MakeScannerAlwaysOn(object obj)
{
_makeScannerAlwaysOnAction = MakeScannerOn;
_makeScannerAlwaysOnAction.BeginInvoke(Callback, null);
}
private void Callback(IAsyncResult ar)
{
FingerPrintScannerDevice.FingerPrintScanner.UnInit();
var objFingerPrintVerifier = new FingerPrintVerifier();
objFingerPrintVerifier.StartVerifingProcess();
var ms = new MemoryStream();
ms.Position = 0;
objFingerPrintVerifier.MatchPerson.Picture.Save(ms, ImageFormat.Png);
var bi = new BitmapImage();
bi.BeginInit();
bi.StreamSource = ms;
bi.EndInit();
Thread.Sleep(2000);
Dispatcher.CurrentDispatcher.Invoke(() => Image = bi);
//Image = bi;
_makeScannerAlwaysOnAction.BeginInvoke(Callback, null);
}
private void MakeScannerOn()
{
while (true)
{
if (FingerPrintScannerDevice.FingerPrintScanner.ScannerManager.Scanners[0].IsFingerOn)
{
return;
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
var handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
}
我的问题: 问题是当我想绑定Image时它会给我错误
必须在与DependencyObject相同的线程上创建DependencySource
我已经google了很多,我在SO中看过这个帖子但是他们都没有为我工作。
任何形式的帮助都将非常感激。
答案 0 :(得分:63)
BitmapImage
是DependencyObject
所以它在哪个线程上创建是很重要的,因为你无法访问在另一个线程上创建的对象的DependencyProperty
,除非它是{{3}对象,你可以Freezable
它。
使当前对象不可修改并将其IsFrozen属性设置为true。
您需要做的是在更新Freeze
之前致电Image
:
bi.BeginInit();
bi.StreamSource = ms;
bi.EndInit();
bi.Freeze();
Dispatcher.CurrentDispatcher.Invoke(() => Image = bi);
如@AwkwardCoder所指出的那样是Freeze