c# - 为什么我收到异常 System.Reflection.TargetInvocationException: 'Exception has been throwed by the target of an invocation.'?
问题描述
ExternalException: A generic error occurred in GDI+.
System.Reflection.TargetInvocationException
HResult=0x80131604
Message=Exception has been thrown by the target of an invocation.
Source=mscorlib
StackTrace:
at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
at System.Delegate.DynamicInvokeImpl(Object[] args)
at System.Windows.Forms.Control.InvokeMarshaledCallbackDo(ThreadMethodEntry tme)
at System.Windows.Forms.Control.InvokeMarshaledCallbackHelper(Object obj)
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.Windows.Forms.Control.InvokeMarshaledCallback(ThreadMethodEntry tme)
at System.Windows.Forms.Control.InvokeMarshaledCallbacks()
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.Run(Form mainForm)
at Extract.Program.Main() in D:\Csharp Projects\Extract\Program.cs:line 19
This exception was originally thrown at this call stack:
System.Drawing.Image.Save(string, System.Drawing.Imaging.ImageCodecInfo, System.Drawing.Imaging.EncoderParameters)
System.Drawing.Image.Save(string, System.Drawing.Imaging.ImageFormat)
Extract.Form1.DownloadAsync() in Form1.cs
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(System.Threading.Tasks.Task)
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(System.Threading.Tasks.Task)
System.Runtime.CompilerServices.TaskAwaiter.GetResult()
Extract.Form1.DownloadImages() in Form1.cs
System.Runtime.CompilerServices.AsyncMethodBuilderCore.ThrowAsync.AnonymousMethod__6_0(object)
Inner Exception 1:
ExternalException: A generic error occurred in GDI+.
列表图像和日期都包含 23 项。异常不是超出索引,而是在最后一项 23 上抛出异常。它在所有图像上绘制文本,但在第 23 项的循环结束时抛出异常。
if (images.Length > 0)
{
for (int i = 0; i < images.Length; i++)
{
drawOnImage.DrawText(dates[i].ToString("ddd, dd MMM yyy HH':'mm"), images[i]);
}
}
也许是因为两个列表包含相同数量的项目 23 ?那我该怎么解决呢?
这是 DownloadAsync 方法的完整代码,在底部我使用 memorystream 和内部带有 drawtext 的循环,异常仅在循环完成时发生在最后一项上。
private async Task DownloadAsync()
{
using (var client = new WebClient())
{
client.DownloadFileCompleted += (s, e) =>
{
if (e.Error == null)
{
urlsCounter--;
var t = urls;
if (urlsCounter == 0)
{
CheckIfImagesExist();
btnRadarPath.Enabled = true;
btnSatellitePath.Enabled = true;
radCounter = 0;
satCounter = 0;
lblStatus.Text = "Completed.";
dates = rad.dates;
var images = System.IO.Directory.GetFiles(radarFolderImagesDownload,
"*.gif", SearchOption.AllDirectories).OrderBy(x => x).ToArray();
Array.Sort(images, new MyComparer(false));
if (images.Length > 0)
{
for (int i = 0; i < images.Length; i++)
{
drawOnImage.DrawText(dates[i].ToString("ddd, dd MMM yyy HH':'mm"), images[i]);
}
}
GetImagesFiles();
}
}
else
{
string error = e.Error.ToString();
}
};
client.DownloadDataCompleted += (s, e) =>
{
if (e.Error == null)
{
urlsCounter--;
var t = urls;
if (urlsCounter == 0)
{
CheckIfImagesExist();
btnRadarPath.Enabled = true;
btnSatellitePath.Enabled = true;
radCounter = 0;
satCounter = 0;
lblStatus.Text = "Completed.";
dates = rad.dates;
var images = System.IO.Directory.GetFiles(radarFolderImagesDownload,
"*.gif", SearchOption.AllDirectories).OrderBy(x => x).ToArray();
Array.Sort(images, new MyComparer(false));
if (images.Length > 0)
{
for (int i = 0; i < images.Length; i++)
{
drawOnImage.DrawText(dates[i].ToString("ddd, dd MMM yyy HH':'mm"), images[i]);
}
}
GetImagesFiles();
}
}
};
client.DownloadProgressChanged += (s, e) => tracker.SetProgress(e.BytesReceived, e.TotalBytesToReceive);
client.DownloadProgressChanged += (s, e) => lblAmount.Text = tracker.SizeSuffix(e.BytesReceived) + "/" + tracker.SizeSuffix(e.TotalBytesToReceive);
client.DownloadProgressChanged += (s, e) => lblSpeed.Text = tracker.GetBytesPerSecondString();
client.DownloadProgressChanged += (s, e) => myLong = Convert.ToInt64(client.ResponseHeaders["Content-Length"]);
client.DownloadProgressChanged += (s, e) =>
{
progressBar1.Value = e.ProgressPercentage;
label1.Text = e.ProgressPercentage + "%";
};
for (int i = 0; i < urls.Count; i++)
{
tracker.NewFile();
if (urls[i].Contains("Radar"))
{
await client.DownloadFileTaskAsync(new Uri(urls[i]), radarFolderImagesDownload + "\\image" + radCounter + ".gif");
radCounter++;
}
else
{
lblStatus.Text = "Downloading satellite";
using (MemoryStream ms = new MemoryStream(await client.DownloadDataTaskAsync(new Uri(urls[i]))))
{
Image img = Image.FromStream(ms, true);
img.Save(satelliteFolderImagesDownload + "\\image" + satCounter + ".gif", System.Drawing.Imaging.ImageFormat.Gif);
}
satCounter++;
}
}
}
}
解决方案
猜测这是发生在与主线程不同的线程中。如果是这样,您需要调用 UI 调用 (DrawText)。为此,您可以将 Invoke 与委托一起使用。为了更彻底,您可以检查InvokeRequired
您是否确实需要调用该调用(即您在不同的线程上)。
Invoke(new Action(() =>
{
drawOnImage.DrawText(dates[i].ToString("ddd, dd MMM yyy HH':'mm"), images[i]);
}));
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