調用線程必須是STA

Question

我試圖模擬一個彈丸，並試圖在定時事件中僅創建一次標簽，因為它在參數中有一個對象，我需要在定時事件中。 但是我運行它時收到此線程錯誤。 請幫助！

我的代碼是：

    void onTimedEvent(Object source, ElapsedEventArgs e)
    {
        particle newProjectile;
        newProjectile = new particle();

        bool LabelExist = false;
        if (LabelExist == false)
        {
            CreateLabels(newProjectile);
        }
    }

        aTimer = new System.Timers.Timer(200);
        aTimer.Elapsed += onTimedEvent;
        aTimer.Enabled = true;

    void CreateLabels(particle newProjectile)
    {
        DockPanel panelcontrol_displacement, panelcontrol_CurrentVel, panelcontrol_VerticalVel, panelcontrol_HorizontalVel, panelcontrol_Time;
        Label lbl_TimeUnits, lbl_TimeOutput, lbl_Time, lbl_DisplacementOutput, lbl_DisplacementUnits, lbl_Displacement, lbl_CurrentVel, lbl_CurrentVelOutput, lbl_HorizontalVelocityOutputs, lbl_HorizontalVelocityUnits, lbl_VerticalVelocity, lbl_HorizontalVelocity, lbl_CurrentVelUnits, lbl_VerticalVelocityOutput, lbl_VerticalVelocityUnits;
        lbl_Time = new Label();
        lbl_Time.Content = "Time";
        lbl_Time.Height = 30;
        lbl_Time.Width = 110;
        lbl_TimeOutput = new Label();
        lbl_TimeOutput.Content = "20";
        lbl_TimeOutput.Height = 30;
        lbl_TimeOutput.Width = 100;
        lbl_TimeOutput.HorizontalContentAlignment = HorizontalAlignment.Right;
        lbl_TimeUnits = new Label();
        lbl_TimeUnits.Content = "s";
        lbl_CurrentVel = new Label();
        lbl_CurrentVel.Content = "Current Velocity";
        lbl_CurrentVel.Height = 30;
        lbl_CurrentVel.Width = 110;
        lbl_CurrentVelOutput = new Label();
        lbl_CurrentVelOutput.Content = "20";
        lbl_CurrentVelOutput.Height = 30;
        lbl_CurrentVelOutput.Width = 100;
        lbl_CurrentVelOutput.HorizontalContentAlignment = HorizontalAlignment.Right;
        lbl_CurrentVelUnits = new Label();
        lbl_CurrentVelUnits.Content = "m/s";
        lbl_VerticalVelocity = new Label();
        lbl_VerticalVelocity.Content = "Verticle Velocity";
        lbl_VerticalVelocity.Height = 30;
        lbl_VerticalVelocity.Width = 110;
        lbl_VerticalVelocityOutput = new Label();
        lbl_VerticalVelocityOutput.Content = "20";
        lbl_VerticalVelocityOutput.Height = 30;
        lbl_VerticalVelocityOutput.Width = 100;
        lbl_VerticalVelocityOutput.HorizontalContentAlignment = HorizontalAlignment.Right;
        lbl_VerticalVelocityUnits = new Label();
        lbl_VerticalVelocityUnits.Content = "m/s";
        lbl_HorizontalVelocity = new Label();
        lbl_HorizontalVelocity.Content = "Horizontal Velocity";
        lbl_HorizontalVelocity.Height = 30;
        lbl_HorizontalVelocity.Width = 110;
        lbl_HorizontalVelocityOutputs = new Label();
        lbl_HorizontalVelocityOutputs.Content = "20";
        lbl_HorizontalVelocityOutputs.Height = 30;
        lbl_HorizontalVelocityOutputs.Width = 100;
        lbl_HorizontalVelocityOutputs.HorizontalContentAlignment = HorizontalAlignment.Right;
        lbl_HorizontalVelocityUnits = new Label();
        lbl_HorizontalVelocityUnits.Content = "m/s";
        lbl_Displacement = new Label();
        lbl_Displacement.Content = "Displacement";
        lbl_Displacement.Height = 30;
        lbl_Displacement.Width = 110;
        lbl_DisplacementOutput = new Label();
        lbl_DisplacementOutput.Content = "20";
        lbl_DisplacementOutput.Height = 30;
        lbl_DisplacementOutput.Width = 100;
        lbl_DisplacementOutput.HorizontalContentAlignment = HorizontalAlignment.Right;
        lbl_DisplacementUnits = new Label();
        lbl_DisplacementUnits.Content = "m/s";
        panelcontrol_HorizontalVel = new DockPanel();
        panelcontrol_CurrentVel = new DockPanel();
        panelcontrol_VerticalVel = new DockPanel();
        panelcontrol_displacement = new DockPanel();
        panelcontrol_Time = new DockPanel();
        panelcontrol_CurrentVel.Children.Add(lbl_CurrentVel);
        panelcontrol_CurrentVel.Children.Add(lbl_CurrentVelOutput);
        panelcontrol_CurrentVel.Children.Add(lbl_CurrentVelUnits);
        panelcontrol_VerticalVel.Children.Add(lbl_VerticalVelocity);
        panelcontrol_VerticalVel.Children.Add(lbl_VerticalVelocityOutput);
        panelcontrol_VerticalVel.Children.Add(lbl_VerticalVelocityUnits);
        panelcontrol_HorizontalVel.Children.Add(lbl_HorizontalVelocity);
        panelcontrol_HorizontalVel.Children.Add(lbl_HorizontalVelocityOutputs);
        panelcontrol_HorizontalVel.Children.Add(lbl_HorizontalVelocityUnits);
        panelcontrol_displacement.Children.Add(lbl_Displacement);
        panelcontrol_displacement.Children.Add(lbl_DisplacementOutput);
        panelcontrol_displacement.Children.Add(lbl_DisplacementUnits);
        panelcontrol_Time.Children.Add(lbl_Time);
        panelcontrol_Time.Children.Add(lbl_TimeOutput);
        panelcontrol_Time.Children.Add(lbl_TimeUnits);
        StkPnl_Inputs.Children.Add(panelcontrol_Time);
        StkPnl_Inputs.Children.Add(panelcontrol_CurrentVel);
        StkPnl_Inputs.Children.Add(panelcontrol_VerticalVel);
        StkPnl_Inputs.Children.Add(panelcontrol_HorizontalVel);
        StkPnl_Inputs.Children.Add(panelcontrol_displacement);
        //databinding
        Binding(newProjectile, lbl_CurrentVelOutput, "CurrentVelocity");
    }

Answer 1

您收到此錯誤，是因為不允許它從后台線程訪問UI（ System.Timers.Timer.Elapsed處理程序正在后台線程上運行）。 這是因為在WPF中處理UI的所有線程都應在Single Threaded Apartment(STA)運行以進行同步。 並且，后台工作者不在STA中運行。

使用DispatcherTimer而不是System.Timers.Timer 。

MSDN頁面的備注部分概述了這兩個計時器之間的區別。

如果在WPF應用程序中使用了System.Timers.Timer，則值得注意的是System.Timers.Timer在不同於用戶界面（UI）線程的線程上運行。 為了訪問用戶界面（UI）線程上的對象，必須使用Invoke或BeginInvoke將操作發布到用戶界面（UI）線程的Dispatcher上。

使用與System.Timers.Timer相對的DispatcherTimer的原因是DispatcherTimer與Dispatcher在同一線程上運行，並且可以在DispatcherTimer上設置DispatcherPriority。