我有两个ViewModel类:PersonViewModel和PersonSearchListViewModel。其中一个字段PersonViewModel实现了通过WCF下载的个人资料图像(在隔离存储中缓存)。PersonSearchListViewModel是一个包含Person列表的容器类。由于加载图像相对较重,PersonSearchListViewModel仅加载当前、下一页和上一页的图像(结果在UI上进行分页)...为了进一步改善图像的加载,我将图像的加载放在了另一个线程上。然而,多线程方法会导致跨线程访问问题。
PersonViewModel:
** 编辑 **
还有一个更奇怪的错误发生。 在下面的代码中:
PersonViewModel:
public void RetrieveProfileImage()
{
Image profileImage = MemorialDataModel.GetImagePerPerson(Person);
if (profileImage != null)
{
MemorialDataModel.ImageManager imgManager = new MemorialDataModel.ImageManager();
imgManager.GetBitmap(profileImage, LoadProfileBitmap);
}
}
private void LoadProfileBitmap(BitmapImage bi)
{
ProfileImage = bi;
// update
IsProfileImageLoaded = true;
}
private BitmapImage profileImage;
public BitmapImage ProfileImage
{
get
{
return profileImage;
}
set
{
profileImage = value;
RaisePropertyChanged(new System.ComponentModel.PropertyChangedEventArgs("ProfileImage"));
}
}
PersonSearchListViewModel:
private void LoadImages()
{
// load new images
Thread loadImagesThread = new Thread(new ThreadStart(LoadImagesProcess));
loadImagesThread.Start();
//LoadImagesProcess(); If executed on the same thread everything works fine
}
private void LoadImagesProcess()
{
int skipRecords = (PageIndex * PageSize);
int returnRecords;
if (skipRecords != 0)
{
returnRecords = 3 * PageSize; // page before, cur page and next page
}
else
{
returnRecords = 2 * PageSize; // cur page and next page
}
var persons = this.persons.Skip(skipRecords).Take(returnRecords);
// load images
foreach (PersonViewModel pvm in persons)
{
if (!pvm.IsProfileImageLoaded)
{
pvm.RetrieveProfileImage();
}
}
}
如何在多线程环境中以ViewModel类的方式处理数据?我知道你必须使用UI调度程序来更新。如何更新绑定到UI的ViewModel?** 编辑 **
还有一个更奇怪的错误发生。 在下面的代码中:
public void GetBitmap(int imageID, Action<BitmapImage> callback)
{
// Get from server
bitmapCallback = callback;
memorialFileServiceClient.GetImageCompleted += new EventHandler<GetImageCompletedEventArgs>(OnGetBitmapHandler);
memorialFileServiceClient.GetImageAsync(imageID);
}
public void OnGetBitmapHandler(object sender, GetImageCompletedEventArgs imageArgs)
{
if (!imageArgs.Cancelled)
{
// I get cross-thread error right here
System.Windows.Media.Imaging.BitmapImage bi = new BitmapImage();
ConvertToBitmapFromBuffer(bi, imageArgs.Result.Image);
// call call back
bitmapCallback.Invoke(bi);
}
}
我在后台线程中尝试创建新的BitmapImage对象时出现了跨线程错误。为什么不能在后台线程中创建新的BitmapImage对象?