c# - 显示表单时出现 ThreadState 异常

Question

我有一个需要几秒钟加载的表单。因此，我想显示一个带有文本“正在加载，请稍候”的小表格。表单加载完成后，必须关闭加载表单。

所以，我做了一个简单的类，它在线程中显示加载表单:

public class ShowLoadingForm
{
    Thread _thread;

    public void Show()
    {
        try
        {
            _thread = new Thread(new ThreadStart(ShowForm));
            _thread.SetApartmentState(ApartmentState.STA);
            _thread.IsBackground = true;
            _thread.Start();
        }
        catch (Exception ex)
        {
            ErrorMessages.UnknownError(true, ex);
        }
    }

    private void ShowForm()
    {
        LoadingForm f = new LoadingForm();
        f.TopMost = true;
        f.ShowInTaskbar = true;
        f.SetText(" Loading... ");
        f.Show();
    }

    public void Close()
    {
        _thread.Abort();
    }
}

在我的主要形式中:

_loadingForm = new ShowLoadingForm();
_loadingForm.Show();

但是。在这段代码之后，我在主窗体上做了一些事情:this.Opacity = 0;。此时，我可以在调试器中看到线程停止工作并抛出 ThreadStateException 并且加载表单消失。

这是为什么？

Answer 1

你的程序崩溃是因为你中止了线程但没有处理窗口。由于 Windows 通知，可能会尝试运行代码，因为线程已中止，这将在 ThreadStateException 上急剧下降。您根本无法通过中止线程来结束线程。

这是解决这个问题的通用类，它负责干净地关闭等待表单和线程。

using System;
using System.Drawing;
using System.Windows.Forms;
using System.Threading;

class Loader : IDisposable {
    private AutoResetEvent initialized = new AutoResetEvent(false);
    private Form loadForm;
    private Rectangle ownerRect;
    private bool closeOkay;

    public Loader(Form owner, Form pleaseWait) {
        if (pleaseWait.IsDisposed) throw new InvalidOperationException("Create a *new* form instance");
        loadForm = pleaseWait;
        loadForm.TopMost = true;
        loadForm.ShowInTaskbar = false;
        loadForm.StartPosition = FormStartPosition.Manual;
        ownerRect = new Rectangle(owner.Location, owner.Size);
        loadForm.Load += delegate {
            loadForm.Location = new Point(
                ownerRect.Left + (ownerRect.Width - loadForm.Width) / 2,
                ownerRect.Top + (ownerRect.Height - loadForm.Height) / 2);
            initialized.Set();
        };
        loadForm.FormClosing += new FormClosingEventHandler((s, ea) => {
            ea.Cancel = !closeOkay;
        });
        var t = new Thread(() => {
            Application.Run(loadForm);
        });
        t.SetApartmentState(ApartmentState.STA);
        t.IsBackground = true;
        t.Start();
        initialized.WaitOne();
    }

    public void Dispose() {
        if (loadForm == null) throw new InvalidOperationException();
        loadForm.Invoke((MethodInvoker)delegate {
            closeOkay = true;
            loadForm.Close(); 
        });
        loadForm = null;
    }

}

示例用法:

    private void button1_Click(object sender, EventArgs e) {
        using (new Loader(this, new LoadingForm())) {
            System.Threading.Thread.Sleep(3000);
        }
    }