vb.net - 扫描条码后无法填写文本框

Question

我正在开发一个条形码扫描程序。TextBox我面临的问题是扫描条形码后无法填写。下面是我的代码。

Private Sub serialPort_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs)
    If TextBox1.Text.Length >= 20 Then
        serialPort.Close()
    Else
        DispString = serialPort.ReadExisting()
    End If
End Sub

Private Sub Form1_Load_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    TextBox1.Focus()
    serialPort.PortName = "COM1"
    serialPort.BaudRate = "9600"
    serialPort.Parity = Parity.None
    serialPort.StopBits = StopBits.One
    serialPort.Handshake = Handshake.None
    serialPort.Open()
    serialPort.ReadTimeout = 200

    If serialPort.IsOpen Then
        DispString = ""
        txtCardKeyDeactivate.Text = ""
    End If

Private Sub SendSerialData(ByVal data As String)
    ' Send strings to a serial port.
    Using COM13 As IO.Ports.SerialPort = My.Computer.Ports.OpenSerialPort("COM1")
        COM13.WriteLine(data)
    End Using
End Sub
Private Sub ReceiveSerialData(ByVal data As String)

    Dim returnStr As String = ""
    Dim COM13 As IO.Ports.SerialPort = Nothing
    Try
        COM13 = My.Computer.Ports.OpenSerialPort("COM1")
        COM13.ReadTimeout = 10000
        Do
            Dim Incoming As String = COM13.ReadLine()
            If Incoming Is Nothing Then
                Exit Do
            Else
                returnStr &= Incoming & vbCrLf
            End If
        Loop
    Catch ex As TimeoutException
        returnStr = "Error: Serial Port read timed out."
    Finally
        If COM13 IsNot Nothing Then COM13.Close()
    End Try
End Sub

标签： vb.netms-access