从另一个线程更新标签的最简单方法是什么?
我在thread1上运行了一个Form,然后我开始另一个线程(thread2)。当thread2处理一些文件时,我想用thread2工作的当前状态更新表单上的标签。
我怎么能这样做?
从另一个线程更新标签的最简单方法是什么?
我在thread1上运行了一个Form,然后我开始另一个线程(thread2)。当thread2处理一些文件时,我想用thread2工作的当前状态更新表单上的标签。
我怎么能这样做?
当前回答
激发并忘记.NET 3.5的扩展方法+
using System;
using System.Windows.Forms;
public static class ControlExtensions
{
/// <summary>
/// Executes the Action asynchronously on the UI thread, does not block execution on the calling thread.
/// </summary>
/// <param name="control"></param>
/// <param name="code"></param>
public static void UIThread(this Control @this, Action code)
{
if (@this.InvokeRequired)
{
@this.BeginInvoke(code);
}
else
{
code.Invoke();
}
}
}
这可以使用以下代码行调用:
this.UIThread(() => this.myLabel.Text = "Text Goes Here");
其他回答
这是一个古老问题的新视角,使用了更实用的风格。如果您在所有项目中都保留TaskXM类,那么只有一行代码不再担心跨线程更新。
public class Example
{
/// <summary>
/// No more delegates, background workers, etc. Just one line of code as shown below.
/// Note it is dependent on the Task Extension method shown next.
/// </summary>
public async void Method1()
{
// Still on the GUI thread here if the method was called from the GUI thread
// This code below calls the extension method which spins up a new task and calls back.
await TaskXM.RunCodeAsync(() =>
{
// Running an asynchronous task here
// Cannot update the GUI thread here, but can do lots of work
});
// Can update GUI on this line
}
}
/// <summary>
/// A class containing extension methods for the Task class
/// </summary>
public static class TaskXM
{
/// <summary>
/// RunCodeAsyc is an extension method that encapsulates the Task.run using a callback
/// </summary>
/// <param name="Code">The caller is called back on the new Task (on a different thread)</param>
/// <returns></returns>
public async static Task RunCodeAsync(Action Code)
{
await Task.Run(() =>
{
Code();
});
return;
}
}
必须使用invoke和delegate
private delegate void MyLabelDelegate();
label1.Invoke( new MyLabelDelegate(){ label1.Text += 1; });
例如,访问当前线程以外的控件:
Speed_Threshold = 30;
textOutput.Invoke(new EventHandler(delegate
{
lblThreshold.Text = Speed_Threshold.ToString();
}));
lblThreshold是一个标签,Speed_Threshold则是一个全局变量。
在这个问题上,大多数其他答案对我来说都有点复杂(我是C#新手),所以我写了我的答案:
我有一个WPF应用程序,并定义了如下工作人员:
问题:
BackgroundWorker workerAllocator;
workerAllocator.DoWork += delegate (object sender1, DoWorkEventArgs e1) {
// This is my DoWork function.
// It is given as an anonymous function, instead of a separate DoWork function
// I need to update a message to textbox (txtLog) from this thread function
// Want to write below line, to update UI
txt.Text = "my message"
// But it fails with:
// 'System.InvalidOperationException':
// "The calling thread cannot access this object because a different thread owns it"
}
解决方案:
workerAllocator.DoWork += delegate (object sender1, DoWorkEventArgs e1)
{
// The below single line works
txtLog.Dispatcher.BeginInvoke((Action)(() => txtLog.Text = "my message"));
}
我还没有弄清楚上面这句话的意思,但它奏效了。
对于WinForms:
解决方案:
txtLog.Invoke((MethodInvoker)delegate
{
txtLog.Text = "my message";
});
激发并忘记.NET 3.5的扩展方法+
using System;
using System.Windows.Forms;
public static class ControlExtensions
{
/// <summary>
/// Executes the Action asynchronously on the UI thread, does not block execution on the calling thread.
/// </summary>
/// <param name="control"></param>
/// <param name="code"></param>
public static void UIThread(this Control @this, Action code)
{
if (@this.InvokeRequired)
{
@this.BeginInvoke(code);
}
else
{
code.Invoke();
}
}
}
这可以使用以下代码行调用:
this.UIThread(() => this.myLabel.Text = "Text Goes Here");