与UI对话的线程

本文关键字：线程 对话 UI | 更新日期: 2023-09-27 18:09:52

我有这样的代码:

private void buttonStart_Click(object sender, EventArgs e)
{
    Task.Factory.StartNew(() => GeneraListaCartelle())
        .ContinueWith(t => GeneraListaCartelleCompletata()
        , CancellationToken.None
        , TaskContinuationOptions.None
        , TaskScheduler.FromCurrentSynchronizationContext());
}
private void GeneraListaCartelle()
{
    try
    {
        ... some operation ....
    }
    catch (Exception err)
    {
        txtErrors.AppendText(err.Message);
    }
}
GeneraListaCartelleCompletata()
{
    ... process finished...
}

和txtErrors在"主"线程(UI)中。当我捕获一个错误时，异步线程不能写入UI控件，我得到一个invalid cross-thread exception。

我可以在线程内与UI对话吗?

与UI对话的线程

如果你使用的是WinForms，你需要在ui线程上调用你的方法，就像

catch (Exception err)
{
    if(this.InvokeRequired){
        Action<Exception> act = ((ex) => {
            txtErrors.AppendText(ex.Message);
        }); 
        this.Invoke(act, new object[] { err });
    }
    else{
        txtErrors.AppendText(err.Message);
    }
}

如果您使用的是WPF，则需要

catch (Exception err)
{
    if(this.Dispatcher.CheckAccess()){
       txtErrors.AppendText(err.Message);
    }
    else {
           Action<Exception> act = ((ex) => {
            txtErrors.AppendText(ex.Message);
           }); 
        this.Dispatcher.Invoke(act, new object[] { err });
    }
}

如果您的目标是WinForm应用程序，那么:

try
    {
        ... some operation ....
    }
catch (Exception err)
    {
       if (txtErrors.InvokeRequired)
        {
            txtErrors.BeginInvoke(new MethodInvoker(
                delegate { txtErrors.AppendText(err.Message); })
                );
        }
    }

有一个来自msdn:

的例子
// This delegate enables asynchronous calls for setting
// the text property on a TextBox control.
delegate void SetTextCallback(string text);
// This method demonstrates a pattern for making thread-safe
// calls on a Windows Forms control. 
//
// If the calling thread is different from the thread that
// created the TextBox control, this method creates a
// SetTextCallback and calls itself asynchronously using the
// Invoke method.
//
// If the calling thread is the same as the thread that created
// the TextBox control, the Text property is set directly.
private void SetText(string text)
{
    // InvokeRequired required compares the thread ID of the
    // calling thread to the thread ID of the creating thread.
    // If these threads are different, it returns true.
    if (this.textBox1.InvokeRequired)
    {
        SetTextCallback d = new SetTextCallback(SetText);
        this.Invoke(d, new object[] { text });
    }
    else
    {
        this.textBox1.Text = text;
    }
}

在调用的form_load事件处理程序中设置CheckForIllegalCrossThreadCalls为false

从一个旧项目中取出，我不得不处理从另一个线程更新UI。应该对你也有用。

delegate void addtoValProg();
addtoValProg myDelegate;
myDelegate = new addtoValProg(invokeControl);
private void GeneraListaCartelle()
{
    try
    {
        //... some operation ....
    }
    catch (Exception err)
    {
        invokeControl();
    }
}
private void invokeControl()
{
    if (this.InvokeRequired)
    {
        this.Invoke(this.myDelegate);
    }
    else
    {
        txtErrors.AppendText(err.Message);
        txtErrors.Update();
    }
}
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