Question

我尝试从另一个线程设置TextBox的Text属性。我在下面得到了这个例外;

"Cross-thread operation not valid: Control 'recTpcTxt' accessed from a thread other than the thread it was created on."

然后，我使用BackgroundWorker来解决这个问题。但是，我遇到了同样的异常消息。

修改[1]： 实际上，我自己就是这个链接; https://msdn.microsoft.com/en-us/library/ms171728(v=vs.110).aspx。我可以使用invokeproperty来解决我的问题。但是，我无法用backgroundworker解决我的问题。

我的解决方案有什么问题吗？如何修复我的解决方案以设置UI变量的某些属性？

编辑[2]： 更多代码以澄清问题;

MqttManager.cs;

public partial class MqttManager : Form
    {
        MqttHandler mqttHandler = new MqttHandler();
        public static MqttManager managerInst;

        public MqttManager()
        {
            InitializeComponent();
            managerInst = this;
            ...
        }

        ...

        private BackgroundWorker backgroundWorker;

        public void NotifyUIForRecMsg(string topic, string message)
        {
            object[] objArr = { topic, message };
            this.backgroundWorker.RunWorkerAsync(objArr);
        }

        private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
        {
            System.Threading.Thread.Sleep(5000);
            e.Result = e.Argument;
        }

        private void backgroundWorker_RunWorkerCompleted(
            object sender,
            RunWorkerCompletedEventArgs e)
        {
            object[] res = (object[])e.Result;
            this.recTpcTxt.Text = (String)res[0];
        }
    }

MqttManager.Design.cs;

partial class MqttManager
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            ...

            this.backgroundWorker = new System.ComponentModel.BackgroundWorker();
            this.backgroundWorker.DoWork += new System.ComponentModel.DoWorkEventHandler(this.backgroundWorker_DoWork);
            this.backgroundWorker.RunWorkerCompleted += new System.ComponentModel.RunWorkerCompletedEventHandler(this.backgroundWorker_RunWorkerCompleted);
        }
        #endregion

        ...
     }

MqttHandler.cs;

class MqttHandler
    {
        MqttClient client;

        ...

        /// <summary>
        /// Publish received event handler.
        /// </summary>
        private void client_MqttMsgPublishReceived(Object sender, MqttMsgPublishEventArgs e)
        {
            MqttManager.managerInst.NotifyUIForRecMsg(e.Topic, Encoding.UTF8.GetString(e.Message));
        }
     }

Answer 1

检查一下： https://msdn.microsoft.com/en-us/library/ms171728(v=vs.110).aspx

基本上，要设置控件属性，您必须位于相同的UI线程中。

这个简单的解决方案将调用移至UI线程中的textbox1.Text = someText

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;
    }
}

另外，您可以使用textBox1.BeginInvoke而不是Invoke：它将在UI线程中运行，而不会锁定调用者线程等待SetText委托完成

[编辑]在你的backgroundWorker中执行：

private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
    object[] arg = (object[])e.Argument;
    SetTextToTextBox(recTpcTxt, (string)arg[0]);
    SetTextToTextBox(recMsgTxt, (string)arg[1]);
}

private void SetTextToTextBox(TextBox toSet, 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 (toSet.InvokeRequired)
    {   
        SetTextCallback d = new SetTextCallback(SetText);
        toSet.Invoke(d, new object[] { text });
    }
    else
    {
        toSet.Text = text;
    }
}

[编辑2] 要正确使用backgroundworker

注册活动DoWork和RunWorkerCompleted

this.backgroundWorker1.DoWork += new System.ComponentModel.DoWorkEventHandler(this.backgroundWorker1_DoWork);
this.backgroundWorker1.RunWorkerCompleted += new System.ComponentModel.RunWorkerCompletedEventHandler(this.backgroundWorker1_RunWorkerCompleted);

退出backgroundWorker1_DoWork之前，请设置eventArgs的结果属性，并在backgroundWorker1_RunWorkerCompleted

中读取它们

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    System.Threading.Thread.Sleep(5000);
    e.Result = new string[] { "one", "two" };
}
private void backgroundWorker1_RunWorkerCompleted(
    object sender,
    RunWorkerCompletedEventArgs e)
{
    string[] res = (string[])e.Result;
    this.textBox1.Text = res[0];
}

如何修复我的后台解决方案以进行线程安全的调用？

1 个答案: