代码上有例外:
private void DownloadProgressCallback(object sender, DownloadProgressChangedEventArgs e)
{
ActiveDownloadJob adJob = e.UserState as ActiveDownloadJob;
if (adJob != null && adJob.ProgressBar != null)
{
adJob.ProgressBar.Invoke((Action)(() => adJob.ProgressBar.Value = e.ProgressPercentage));
}
}
在线上:
adJob.ProgressBar.Invoke((Action)(() => adJob.ProgressBar.Value = e.ProgressPercentage));
这是form1中的ActiveDownloadJob类:
class ActiveDownloadJob
{
public DownloadImages.DownloadData DownloadData;
public ProgressBar ProgressBar;
public WebClient WebClient;
public ActiveDownloadJob(DownloadImages.DownloadData downloadData, ProgressBar progressBar, WebClient webClient)
{
try
{
this.DownloadData = downloadData;
this.ProgressBar = progressBar;
this.WebClient = webClient;
}
catch (Exception err)
{
MessageBox.Show(err.ToString());
}
}
}
我不确定我是否需要调用此行,因为我现在不使用backgroundworker,但我不确定。
这是完整的异常消息:在创建窗口句柄之前,无法在控件上调用Invoke或BeginInvoke
System.InvalidOperationException was unhandled by user code
HResult=-2146233079
Message=Invoke or BeginInvoke cannot be called on a control until the window handle has been created.
Source=System.Windows.Forms
StackTrace:
at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)
at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)
at System.Windows.Forms.Control.Invoke(Delegate method)
at WeatherMaps.Form1.DownloadProgressCallback(Object sender, DownloadProgressChangedEventArgs e) in d:\C-Sharp\WeatherMaps\WeatherMaps\WeatherMaps\Form1.cs:line 290
at System.Net.WebClient.OnDownloadProgressChanged(DownloadProgressChangedEventArgs e)
at System.Net.WebClient.ReportDownloadProgressChanged(Object arg)
InnerException:
我如何在不使用Invoke的情况下将该行更改为?如果需要Invoke,如何修复该行和异常?
我知道我应该在Form1表单关闭事件中处理它,但是如何?在form1表单关闭事件中我该怎么办?
是的,您会收到一个异常,因为Invoke
需要将“消息”发布到“消息循环”,但Handle
尚未创建。
使用InvokeRequired
就看你是否需要Invoke
,当调用它不会创建拉手又是那么直接,这将返回false。
var method = (Action)(() => adJob.ProgressBar.Value = e.ProgressPercentage);
if(adJob.ProgressBar.InvokeRequired)
adJob.ProgressBar.Invoke(method);
else
method();
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我来说两句