c# - 线程和 ArcGIS

Question

我刚刚偶然发现了 Backgroundworker 对象，它似乎是我正在寻找的工具，可以让我的 GUI 在执行计算时做出响应。我正在为 ArcGIS 编写 IO 插件。

我正在 ArcGIS 之外进行一些数据处理，使用后台工作器可以正常工作。但是当我将数据插入 ArcGIS 时，后台工作人员似乎将持续时间增加了 9 倍左右。将处理代码放在 DoWork 方法之外，可将性能提高 9 倍。

我已经在网上的几个地方读到过这方面的内容，但我没有多线程编程方面的经验，而且像 STA 和 MTA 这样的术语对我来说毫无意义。 link text我也尝试过使用简单的线程实现，但结果相似。

有谁知道我可以做些什么来使用 ArcGIS 处理和维护响应式 GUI？

编辑:我已经包含了我与后台工作人员互动的示例。如果我将位于 StartImporting 方法中的代码放在 cmdStart_Click 方法中，它的执行速度会快得多。

private void StartImporting(object sender, DoWorkEventArgs e)
{
    DateTime BeginTime = DateTime.Now;
    // Create a new report object.
    SKLoggingObject loggingObject = new SKLoggingObject("log.txt");
    loggingObject.Start("Testing.");

    SKImport skImporter = new SKImport(loggingObject);
    try
    {
        // Read from a text box - no writing.
    skImporter.Open(txtInputFile.Text);
    }
    catch
    {
    }
    SKGeometryCollection convertedCollection = null;

    // Create a converter object.
    GEN_SK2ArcGIS converter = new GEN_SK2ArcGIS(loggingObject);

    // Convert the data.
    convertedCollection = converter.Convert(skImporter.GetGeometry());

    // Create a new exporter.
    ArcGISExport arcgisExporter = new ArcGISExport(loggingObject);

    // Open the file.            
    // Read from a text box - no writing.
    arcgisExporter.Open(txtOutputFile.Text);

    // Insert the geometry collection.
    try
    {
    arcgisExporter.Insert(convertedCollection);
    }
    catch
    {
    }
    TimeSpan totalTime = DateTime.Now - BeginTime;
    lblStatus.Text = "Done...";

}

private void ChangeProgress(object sender, ProgressChangedEventArgs e) 
{
    // If any message was passed, display it.
    if (e.UserState != null && !((string)e.UserState).Equals(""))
    {
    lblStatus.Text = (string)e.UserState;
    }
    // Update the progress bar.
    pgStatus.Value = e.ProgressPercentage;
}

private void ImportDone(object sender, RunWorkerCompletedEventArgs e)
{
    // If the process was cancelled, note this.
    if (e.Cancelled)
    {
    pgStatus.Value = 0;
    lblStatus.Text = "Operation was aborted by user...";
    }
    else
    {
    }

}

private void cmdStart_Click(object sender, EventArgs e)
{
    // Begin importing the sk file to the geometry collection.

    // Initialise worker.
    bgWorker = new BackgroundWorker();
    bgWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(ImportDone);
    bgWorker.ProgressChanged += new ProgressChangedEventHandler(ChangeProgress);
    bgWorker.DoWork += new DoWorkEventHandler(StartImporting);
    bgWorker.WorkerReportsProgress = true;
    bgWorker.WorkerSupportsCancellation = true;

    // Start worker.
    bgWorker.RunWorkerAsync();

}

private void cmdCancel_Click(object sender, EventArgs e)
{
    bgWorker.CancelAsync();
}

亲切的问候，卡斯珀

Answer 1

在 ArcGIS 中使用 COM 对象时，应该使用 STA 线程是正确的。不过，您仍然可以获得 BackgroundWorker 的便利，它始终是系统线程池中的 MTA 线程。

private static void OnBackgroundWorkerDoWork(object sender, DoWorkEventArgs e)
{
    BackgroundWorker worker = (BackgroundWorker)sender;
    ToolToStart tool = e.Argument as ToolToStart;

    if (tool != null)
    {
        tool.BackgroundWorker = worker;

        // The background worker thread is an MTA thread, 
        // and should not operate on ArcObjects/COM types.
        // Instead we create an STA thread to run the tool in.
        // When the the tool finishes the infomation from the STA thread 
        // is transferred to the background worker's event arguments.
        Thread toolThread = new Thread(STAThreadStart);
        toolThread.SetApartmentState(ApartmentState.STA);
        toolThread.Start(tool);

        toolThread.Join();
        e.Cancel = m_ToolCanceled;
        e.Result = m_ToolResult;
    }
}

STA 线程现在可以使用 BackgroundWorker 的方法，例如报告进度、检查取消和报告结果。

protected virtual void StatusUpdateNotify(ProgressState progressState)
{
    if (BackgroundWorker.CancellationPending)
    {
        throw new OperationCanceledException();
    }

    BackgroundWorker.ReportProgress(progressState.Progress, progressState);
}

除了在操作 ArcGIS 对象时仅使用 STA 线程外，您不应在两个线程之间共享对象。从您的代码看来，您似乎是从后台工作人员访问 GUI 的:lblStatus.Text = "Done...";，这可以在例如RunWorkerComplete 的委托(delegate)。