当外部类中的变量发生变化时，如何更新LiveCharts笛卡儿图？

Question

我最近买了一台脑电耳机(NeuroSky MindWave Mobile)。它只是一个戴在头上捕捉脑电波数据的装置。该设备通过蓝牙实时传输这些数据，然后可以通过软件程序进行读取/分析。

NeuroSky提供了一组易于使用的API，我用它编写了一个基本类来读取流耳机数据。它的简略版本如下：

using System;
using NeuroSky.ThinkGear;


namespace MindWave_Reader
{
    class ReadEEG
    {
        public double AlphaValue { get; set; }
        private Connector connector;

        public ReadEEG()
        {
            // Initialize a new Connector and add event handlers
            connector = new Connector();
            connector.DeviceConnected += new EventHandler(OnDeviceConnected);

            // Scan for headset on COM7 port
            connector.ConnectScan("COM7");
        }


        // Called when a device is connected
        public void OnDeviceConnected(object sender, EventArgs e) {
            Connector.DeviceEventArgs de = (Connector.DeviceEventArgs)e;

            Console.WriteLine("Device found on: " + de.Device.PortName);
            de.Device.DataReceived += new EventHandler(OnDataReceived);
        }


        // Called when data is received from a device
        public void OnDataReceived(object sender, EventArgs e) {
            Device.DataEventArgs de = (Device.DataEventArgs)e;
            DataRow[] tempDataRowArray = de.DataRowArray;

            TGParser tgParser = new TGParser();
            tgParser.Read(de.DataRowArray);

            /* Loops through the newly parsed data of the connected headset */
            for (int i = 0; i < tgParser.ParsedData.Length; i++) {
                if(tgParser.ParsedData[i].ContainsKey("EegPowerAlpha")) {
                    AlphaValue = tgParser.ParsedData[i]["EegPowerAlpha"];
                    Console.WriteLine("Alpha: " + AlphaValue);
                }
            }
        }
    }
}

上述代码首先尝试连接到EEG耳机。一旦连接完毕，每次从耳机接收数据时，都会调用OnDataReceived()。此方法将相关的流耳机数据值(alpha waves)打印到控制台。

现在我想在笛卡儿图上实时显示这些α波值，我发现了LiveCharts，它看起来像一个整洁的图形库。这个WinForms示例与我所要达到的目标是一致的。

阿尔法波值应与X轴上的时间相对应，绘制在Y轴上。但是，与其像示例中那样每500 is更新一次图表，我希望它只在从耳机接收数据时更新(换句话说，当AlphaValue变量在ReadEEG类中由OnDataReceived()更新时)。

我想知道如何让我的WinForm与ReadEEG类交互，以这种方式更新其笛卡尔图。我是个新手，所以任何帮助都会受到极大的感谢。

我真的希望我已经说得很清楚，并尽量使解释尽量简单。如果你有任何问题，不要犹豫。提前感谢您的帮助！

Answer 1

有一种方法你可以做到。我向ReadEEG类添加了一个新事件。只要有新的AlphaValue，就会引发这个新事件。在主表单中，它订阅此事件并将新值添加到ChartValues集合中，这是LiveChart上显示的内容。

using System;
using System.Data;
using NeuroSky.ThinkGear;

namespace MindWave_Reader
{
  class ReadEEG
  {
    public double AlphaValue { get; set; }
    private Connector connector;

    public ReadEEG()
    {
      // Initialize a new Connector and add event handlers
      connector = new Connector();
      connector.DeviceConnected += new EventHandler(OnDeviceConnected);

      // Scan for headset on COM7 port
      connector.ConnectScan("COM7");
    }

    // Called when a device is connected
    public void OnDeviceConnected(object sender, EventArgs e)
    {
      Connector.DeviceEventArgs de = (Connector.DeviceEventArgs)e;

      Console.WriteLine("Device found on: " + de.Device.PortName);
      de.Device.DataReceived += new EventHandler(OnDataReceived);
    }

    // Called when data is received from a device
    public void OnDataReceived(object sender, EventArgs e)
    {
      Device.DataEventArgs de = (Device.DataEventArgs)e;
      DataRow[] tempDataRowArray = de.DataRowArray;

      TGParser tgParser = new TGParser();
      tgParser.Read(de.DataRowArray);

      /* Loops through the newly parsed data of the connected headset */
      for (int i = 0; i < tgParser.ParsedData.Length; i++)
      {
        if (tgParser.ParsedData[i].ContainsKey("EegPowerAlpha"))
        {
          AlphaValue = tgParser.ParsedData[i]["EegPowerAlpha"];
          Console.WriteLine("Alpha: " + AlphaValue);
          // Raise the AlphaReceived event with the new reading.
          OnAlphaReceived(new AlphaReceivedEventArgs() { Alpha = AlphaValue });
        }
      }
    }

    /// <summary>
    /// The arguments for the <see cref="AlphaReceived"/> event.
    /// </summary>
    public class AlphaReceivedEventArgs : EventArgs
    {
      /// <summary>
      /// The alpha value that was just received.
      /// </summary>
      public double Alpha { get; set; }
    }

    /// <summary>
    /// Raises the <see cref="AlphaReceived"/> event if there is a subscriber.
    /// </summary>
    /// <param name="e">Contains the new alpha value.</param>
    protected virtual void OnAlphaReceived(AlphaReceivedEventArgs e)
    {
      AlphaReceived?.Invoke(this, e);
    }

    /// <summary>
    /// Event that gets raised whenever a new AlphaValue is received from the
    /// device.
    /// </summary>
    public event EventHandler AlphaReceived;
  }
}

在Form1上，我在设计器中添加了一个LiveCharts.WinForms.CartesianChart。后面的代码如下：

using LiveCharts;
using LiveCharts.Configurations;
using LiveCharts.Wpf;
using System;
using System.Windows.Forms;
using static MindWave_Reader.ReadEEG;

namespace MindWave_Reader
{
  public partial class Form1 : Form
  {
    /// <summary>
    /// Simple class to hold an alpha value and the time it was received. Used
    /// for charting.
    /// </summary>
    public class EEGPowerAlphaValue
    {
      public DateTime Time { get; }
      public double AlphaValue { get; }

      public EEGPowerAlphaValue(DateTime time, double alpha)
      {
        Time = time;
        AlphaValue = alpha;
      }
    }

    private ReadEEG _readEEG;

    /// <summary>
    /// Contains the alpha values we're showing on the chart.
    /// </summary>
    public ChartValues<EEGPowerAlphaValue> ChartValues { get; set; }

    public Form1()
    {
      InitializeComponent();

      // Create the mapper.
      var mapper = Mappers.Xy<EEGPowerAlphaValue>()
          .X(model => model.Time.Ticks)   // use Time.Ticks as X
          .Y(model => model.AlphaValue);  // use the AlphaValue property as Y

      // Lets save the mapper globally.
      Charting.For<EEGPowerAlphaValue>(mapper);

      // The ChartValues property will store our values array.
      ChartValues = new ChartValues<EEGPowerAlphaValue>();
      cartesianChart1.Series = new SeriesCollection
      {
        new LineSeries
        {
          Values = ChartValues,
          PointGeometrySize = 18,
          StrokeThickness = 4
        }
      };

      cartesianChart1.AxisX.Add(new Axis
      {
        DisableAnimations = true,
        LabelFormatter = value => new DateTime((long)value).ToString("mm:ss"),
        Separator = new Separator
        {
          Step = TimeSpan.FromSeconds(1).Ticks
        }
      });

      SetAxisLimits(DateTime.Now);
    }

    private void StartButton_Click(object sender, EventArgs e)
    {
      _readEEG = new ReadEEG();
      _readEEG.AlphaReceived += _readEEG_AlphaReceived;
    }

    /// <summary>
    /// Called when a new alpha value is received from the device. Updates the
    /// chart with the new value.
    /// </summary>
    /// <param name="sender">The <see cref="ReadEEG"/> object that raised this
    /// event.</param>
    /// <param name="e">The <see cref="AlphaReceivedEventArgs"/> that contains
    /// the new alpha value.</param>
    private void _readEEG_AlphaReceived(object sender, EventArgs e)
    {
      AlphaReceivedEventArgs alphaReceived = (AlphaReceivedEventArgs)e;

      // Add the new alpha reading to our ChartValues.
      ChartValues.Add(
        new EEGPowerAlphaValue(
          DateTime.Now,
          alphaReceived.Alpha));

      // Update the chart limits.
      SetAxisLimits(DateTime.Now);

      // Lets only use the last 30 values. You may want to adjust this.
      if (ChartValues.Count > 30)
      {
        ChartValues.RemoveAt(0);
      }
    }

    private void SetAxisLimits(DateTime now)
    {
      if (cartesianChart1.InvokeRequired)
      {
        cartesianChart1.Invoke(new Action(() => SetAxisLimits(now)));
      }
      else
      {
        // Lets force the axis to be 100ms ahead. You may want to adjust this.
        cartesianChart1.AxisX[0].MaxValue =
          now.Ticks + TimeSpan.FromSeconds(1).Ticks;

        // We only care about the last 8 seconds. You may want to adjust this.
        cartesianChart1.AxisX[0].MinValue =
          now.Ticks - TimeSpan.FromSeconds(8).Ticks;
      }
    }
  }
}