C# 移动扫描器值表现得很奇怪

Question

所以我写了一个快速示例程序来更好地理解 Janam 扫描枪，但是我遇到了我从未见过的问题，尽管我认为可能是由于在不同的线程上并在它们之间传递值造成的。所以我认为我没有正确使用委托(delegate)。并提供帮助。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using Scanner;

namespace ScannerTest
{
public partial class Form1 : Form
{
    //Delegates
    private delegate void RefreshValuesDelegate();
    private delegate void AddScannedItemDelegate(Item item);
    // SINGLETON //////////////////////////////////////
    private static Form1 instance = null;

    public static Form1 GetInstance()
    {
        if (instance == null)
            instance = new Form1();

        return instance;
    }
    ///////////////////////////////////////////////////

    public Form1()
    {
        InitializeComponent();
    }
    void Form1_Load(object sender, EventArgs e)
    {
        /**************/
        //SCANNER ACTIVATE                       

        GlobalScanner.GetInstance().Close();
        GlobalScanner.GetInstance().BarcodeDelegateDirector = new GlobalScanner.BarcodeDelegate(Form1.GetInstance().processScannedBarcode);
        GlobalScanner.GetInstance().Open();
        /**************/

    }
    // Add the new part unless the part number contains 
    // spaces. In that case cancel the add. 
    private void button1_Click(object sender, EventArgs e)
    {
        if (textBox1.Text.Equals("") || textBox2.Text.Equals(""))
        {
            MessageBox.Show("item names or barcodes cannot be blank.");
        }
        else
        {
            Item temp = new Item(textBox1.Text, textBox2.Text, DateTime.Now);
            if (temp.ItemCheck == true)
            {
                AddToList(temp);
            }
        }
    }
    public void processScannedBarcode(string scannedBarcode)
    {
        if (scannedBarcode != null && scannedBarcode.Length > 0) // 0 = SUCCESS Symbol.Results.SUCCESS
        {
            Item temp = new Item();
            temp.ItemName = "N/A";
            temp.BarcodeNumber = scannedBarcode;
            String tempDate = DateTime.Now.ToShortDateString();
            String tempTime = DateTime.Now.ToShortTimeString();
            temp.ScanDate = tempDate + tempTime;
            AddScannedItem(temp);
        }
    }
    private void AddScannedItem(Item item)
    {
        if (this.InvokeRequired == true)
        {
            this.Invoke(new AddScannedItemDelegate(AddScannedItem), new object[] { item });
        }
        else
        {
            this.textBox2.Text = item.BarcodeNumber;
            this.textBox1.Text = item.ItemName; // description not available
            item.ScanDate = DateTime.Now.ToLongDateString();
            //DateTime readDate = DateTime.Now;
            //cargo.SetReadDate(readDate);
            RefreshValues();
            AddToList(item);
        }
    }
    private void AddToList(Item item)
    {
        string tempItem = item.ItemName;
        string tempBarcode = item.BarcodeNumber;
        string tempDate = item.ScanDate;
        ListViewItem newRow = new ListViewItem(tempItem);
        newRow.SubItems.Add(tempBarcode);
        newRow.SubItems.Add(tempDate);
        listView1.Items.Add(newRow);
        RefreshValues();
        //MessageBox.Show(string.Format("TextBox1: {0} TextBox2: {1}", tempItem, tempBarcode));
        textBox2.Text = "";
        textBox1.Text = "";
    }
    public void RefreshValues()
    {
        if (this.InvokeRequired == true)
        {
            this.Invoke(new RefreshValuesDelegate(RefreshValues));
        }
        else
        {
            listView1.Refresh();
        }
    }
}

// A simple business object for example purposes. 
public class Item
{
    private string name;
    private string number;
    private string date;
    private bool check = true;

    public Item() { }
    public Item(string nameForItem, string numberForBarcode, DateTime scandate)
    {
        ItemName = nameForItem;
        BarcodeNumber = numberForBarcode;
        date = scandate.ToShortDateString();
    }

    public string ItemName
    {
        get 
        { 
            return name; 
        }
        set 
        {
            if (value.Length <= 45)
            {
                name = value;
            }
            else
            {
                MessageBox.Show("Item name to long. Must be less than 45 characters.");
                ItemCheck = false;
            }
        }
    }

    public string BarcodeNumber
    {
        get 
        { 
            return number; 
        }
        set 
        {
            if (value.Length <= 20)
            {
                number = value; 
            }
            else
            {
                MessageBox.Show("Barcode is to long. Must be less than 20 digits.");
                ItemCheck = false;
            }
        }
    }
    public string ScanDate
    {
        get
        {
            return date;
        }
        set
        {
            date = value;
        }
    }

    public bool ItemCheck
    {
        get
        {
            return check;
        }
        set
        {
            check = value;
        }
    }
}
}

因此手动输入值可以正常工作，但是当扫描仪被激活并读入一个值时。调试器显示在代码通过列表时设置和存储的正确值，但是屏幕上没有显示来自扫描仪的任何内容，也不会像手动键入时那样将值保存到 ListView 中。

就像我之前说的那样，我认为委托(delegate)和扫描器线程将值传递给它不喜欢的主线程是一个问题。

提前感谢您的帮助。

这是手动输入值的 View

这是正在使用的扫描仪的 View 。我取消了对消息框的注释，这样您就可以看到它正在拾取一些东西。

回答某人的问题:

这是供那些想要检查它的人使用的全局扫描仪。

using System;
using System.Linq;
using System.Collections.Generic;
using System.Text;

namespace Scanner
{
public class GlobalScanner
{
    #region About using the delegate in this class
    /*  We are actually using one central class to do the scanning, but user can scan from different screens.
      * If we don't have a delegate we will have the following scenario. We scan the barcode, the barcode will be 
      * captured in our scanner implementation class "For example: IntermecBarcodeScanner" and we will have no way to return
      * the barcode back to the scanning screen. The delegate will actually help us to do that job. The delegate will
      * be associated with a method inside the scanning form. It will carry the scanned barcode over to that method
      * inside the scanning form.
      * 
      * We need 3 main things to get the delegate working:
      * 1- Declare a delegate variable
           public delegate void BarcodeDelegate(string barcode);
      * 2- Initialize a delegate and associate it with the appropropriate method in the scanning form: 
      *     Example: GlobalScanner.GetInstance().BarcodeDelegateDirector = new GlobalScanner.BarcodeDelegate(this.ScanBarcodeEvent);
      *     We need the above line of code to be in the scanning form. That's how we associate the ScanBarcodeEvent() method
      *     with the delegate that is in the GlobalScanner class.
      * 3- In GlobalScanner class we created two variables to help us to connect to the scanner implementation class such as
      *    the IntermecBarcodeScanner. Those two variables are: barcodeDelegateInstance and barcodeData
      */
    #endregion

    //Declare a delegate
    public delegate void BarcodeDelegate(string barcode);

    private IBarcodeScanner scanner = null;

    // SINGLETON //////////////////////////////////////
    private static GlobalScanner instance = null;

    public static GlobalScanner GetInstance()
    {
        if (instance == null)
        {
            instance = new GlobalScanner();
        }

        return instance;
    }
    // ////////////////////////////////////////////////


    private BarcodeDelegate barcodeDelegateInstance = null;
    //BarcodeDelegateDirector will be accessed to associate the method 
    //that's in the scanning form with the delegate
    public  BarcodeDelegate BarcodeDelegateDirector
    {
        get { return barcodeDelegateInstance; }
        set { barcodeDelegateInstance = value; }
    }

    //We also created this variable to set the barcode value from other classes such as IntermecBarcodeScanner
    private string barcodeData;
    public string BarcodeData
    {
        get { return barcodeData; }
        set
        {
            barcodeData = value;
            barcodeDelegateInstance(barcodeData); //barcodeData is the scanned barcode and it comes from the GlobalScanner implementation
        }
    }

    public void Open()
    {
        String deviceName = Platform.GetOEMInfo();
        if (deviceName != null)
        {                
            if (scanner == null)
            {
                if (deviceName.Equals(Global.INTERMEC_DEVICE_1) || deviceName.Equals(Global.INTERMEC_DEVICE_2) || deviceName.Equals(Global.INTERMEC_DEVICE_3))
                    scanner = new IntermecBarcodeScanner();
                else if (deviceName.Equals(Global.JANAM_DEVICE_1) || deviceName.Equals(Global.JANAM_DEVICE_2) || deviceName.Equals(Global.JANAM_DEVICE_3))
                    scanner = new JanamXMBarcodeScanner();
                else if (deviceName.Equals(Global.JANAM_XG_DEVICE_1) || deviceName.Equals(Global.JANAM_XG_DEVICE_2) || deviceName.Equals(Global.JANAM_XG_DEVICE_3))
                    scanner = new JanamXGBarcodeScanner();
                else if (deviceName.Equals(Global.MOTOROLA_DEVICE_1) || deviceName.Equals(Global.MOTOROLA_DEVICE_2) || deviceName.Equals(Global.MOTOROLA_DEVICE_3))
                    scanner = new MotorolaBarcodeScanner();

            }

            scanner.Open();
        }
    }

    public void Close()
    {
        if (scanner != null)
        {
            scanner.Close();
        }

    }
}
}

Answer 1

如果您认为这是一个线程间问题，您可以使用锁对象来确保只有一个线程可以访问事件数据:

一个全局性的 对象锁定对象 = 新对象()；必须定义并在 AddToList 中用 锁(锁对象) { }以上确保一次只有一个 AddToList 在运行。

我在使用条形码扫描仪的委托(delegate)中看到的另一个差异是委托(delegate)用法:在我的代码中，我首先声明委托(delegate)的新 var，然后调用 var 上的 invoke。但这不应该对功能产生影响。