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[英]UWP C# System.UnauthorizedAccessException when saving XML file
[英]System.UnauthorizedAccessException when saving image from Scheduled Agent
我正在构建一个WP8应用程序,该应用程序使用来自Internet的图像来更改锁屏的背景。 我按照计划的代理和锁定屏幕进行了教程学习,但是遇到了问题。
当我尝试从Scheduled Agent下载新的背景图像时,得到以下信息:
+ $exception {System.UnauthorizedAccessException: Invalid cross-thread access.
at MS.Internal.XcpImports.CheckThread()
at System.Windows.DependencyObject..ctor(UInt32 nativeTypeIndex, IntPtr constructDO)
at System.Windows.Media.Imaging.BitmapImage..ctor()
at TileLockAgent.ScheduledAgent.lockScreenClient_OpenReadCompleted(Object sender, OpenReadCompletedEventArgs e)
at System.Net.WebClient.OnOpenReadCompleted(OpenReadCompletedEventArgs e)
at System.Net.WebClient.OpenReadOperationCompleted(Object arg)
at System.Threading.WaitCallback.Invoke(Object state)
at System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(Object state)
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.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
at System.Threading.ThreadPoolWorkQueue.Dispatch()
at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()} System.Exception {System.UnauthorizedAccessException}
代码是:
string fileName;
try
{
var currentImage = LockScreen.GetImageUri();
if (currentImage.ToString().EndsWith("_1.jpg"))
{
fileName = "LockBackground_2.jpg";
}
else
{
fileName = "LockBackground_1.jpg";
}
}
catch
{
// lockscreen not set or prev owned by other app
fileName = "LiveLockBackground_1.jpg";
}
using (var isoStore = IsolatedStorageFile.GetUserStoreForApplication())
{
var bi = new BitmapImage();
bi.SetSource(e.Result);
var wb = new WriteableBitmap(bi);
using (var isoFileStream = isoStore.CreateFile(fileName))
{
var width = wb.PixelWidth;
var height = wb.PixelHeight;
Extensions.SaveJpeg(wb, isoFileStream, width, height, 0, 100);
}
}
我真的不知道该怎么解决。 如果BitmapImage无法正常工作,如何将图像保存在预定的代理中? 我正在执行“跨线程访问”是什么意思? 映像仅由计划的代理创建和使用,因此没有人可以访问它们。
该问题是由于无法在UI线程外部实例化BitmapImage引起的。 您可以通过将呼叫包装在Dispatcher Invoke呼叫中来解决此问题。
但是,您需要确保正确调用NotifyComplete。 因此,您可能需要将NotifyComplete放入Dispatcher调用中。
Deployment.Current.Dispatcher.BeginInvoke(() =>
{
UpdateSyncPictureName(...);
NotifyComplete();
});
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