Question

我正在使用后台工作程序读取值，并将值传递给Worker_ProgressChanged，以更新UI。

在Worker_DoWork中：

while (agi.DvmReadyToRead)   // wait for digipot to be adjusted before reading in worker
{
    Thread.Sleep(20);
    Application.DoEvents();
    //logS.Debug("Waiting for ready to read in worker");
}
Thread.Sleep(40);  // Give digipot chance to make the change
agi.SendSoftwareTriggerOne();
Thread.Sleep(7);    // Duration for above command to execute
A = agi.ReadOne();
Thread.Sleep(1);    
agi.InitOne();
Thread.Sleep(1);    
sAndH3 = A[0];
worker.ReportProgress(0, new System.Tuple<double>(sAndH3));
agi.DvmReadyToRead = true;

在Worker_ProgressChanged中：

while (!agi.DvmReadyToRead)
{
    //logS.Debug("waiting for ready to read in progress");
    Thread.Sleep(0);
    Thread.Sleep(0);
    Thread.Sleep(0);
    Thread.Sleep(0);
    Thread.Sleep(0);
    Application.DoEvents();  // Exception thown here
    Thread.Sleep(1);     // wait for DVM reading
}
agi.DvmReadyToRead = false;

// Then goes on to adjust output voltage up or down

第一次使用

可以正常工作

Application.DoEvents();

但是，第一次运行后，此时我得到了stackoverflow。在这里阅读了很多文章之后，DoEvents并不是实现我想要实现的最佳方法。因此，我想要的是将布尔值传递回DoWork的方法，或者是允许工作人员能够读取agi.DvmReadyToRead布尔值的另一种方法。

谢谢！

Answer 1

如果我理解您的问题，那么您将在“测试和测量”中描述一个非常常见的模式，即您拥有一台仪器，在触发它之后需要一些时间才能获得读数。但是您想知道何时发生读取，以便可以采取一些措施（例如更新ProgressBar或TextBox），并且希望能够取消工作程序循环。

当我需要自己执行此操作时，我喜欢使用System.Threading.Tasks简化操作。我将在此处发布一个完整的模式，希望您能找到一些有用的方法来解决您遇到的问题。

为了清楚起见，我试图回答您的“将布尔值传递回DoWork的方法...”的问题，方法是说一种方法是从Worker_DoWork触发一个可以包含布尔值的事件（例如您询问）或加倍（在我的示例中）或您选择的任何其他信息。

祝你好运！

using System;
using System.ComponentModel;    
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace StackOverflow02
{
    public partial class DVMLoopRunner : Form
    {
        public DVMLoopRunner()
        {
            InitializeComponent();
            DVMReadingAvailable += Form1_DVMReadingAvailable;
            ContinueOrCancel += Form1_ContinueOrCancel;
        }

        // See if User has turned off the Run button then cancel worker
        private void Form1_ContinueOrCancel(Object sender, CancelEventArgs e)
        {
            e.Cancel = !checkBoxRunMeterLoop.Checked;
        }

        // The DVM, after being triggered + some delay, has come up with a new reading.
        private void Form1_DVMReadingAvailable(Object sender, DVMReadingAvailableEventArgs e)
        {
            // To update GUI from worker thread requires Invoke to prevent Cross-Thread Exception
            Invoke((MethodInvoker)delegate
            {
                textBox1.Text = e.Reading.ToString("F4");
            });
        }

        // Make our events so that we can be notified of things that occur
        public event CancelEventHandler ContinueOrCancel;                   
        public event DVMReadingAvailableEventHandler DVMReadingAvailable;

        // This is how we will provide info to the GUI about the new reading
        public delegate void DVMReadingAvailableEventHandler(Object sender, DVMReadingAvailableEventArgs e);
        public class DVMReadingAvailableEventArgs : EventArgs
        {
            public readonly double Reading;
            public DVMReadingAvailableEventArgs(double reading)
            {
                Reading = reading;
            }
        }

        // When the User checks the box, Run the worker loop
        private void checkBoxRunMeterLoop_CheckedChanged(Object sender, EventArgs e)
        {
            if(checkBoxRunMeterLoop.Checked)
            {
                Task.Run(() => ReadDVMWorker());
            }
        }

        // Worker Loop
        private void ReadDVMWorker()
        {
            while(true)
            {
                CancelEventArgs e = new CancelEventArgs();
                ContinueOrCancel?.Invoke(this, e);
                if (e.Cancel) return;               // If User has turned off the Run button then stop worker
                ReadDVM();                          // This worker thread will block on this. So trigger, wait, etc.
            }
        }

        // DVM Takes some period of time after trigger
        void ReadDVM()
        {
            Thread.Sleep(1000);
            double newSimulatedReading = 4.5 + Random.NextDouble();
            DVMReadingAvailable?.Invoke(this, new DVMReadingAvailableEventArgs(newSimulatedReading));
        }
        Random Random = new Random();   // Generate random readings for simulation
    }
}

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1 个答案: