Question

我的vb.net应用程序出现问题，该应用程序使用RFID MFRC522和Arduino到Visual Basic。来自Arduino串口的数据已成功发送到VB.net文本框。如果文本框仅从Arduino（卡片标签的UUID）接收到特定数据，那么如果有匹配的卡片标签，则会检索SQL中的数据。

扫描时检索数据并自动保存没有问题。唯一的问题是我扫描RFID标签。 UUID被转移到文本框，没有数据出现在标签上。但是，当我单击文本框内的UUID卡标记的末尾并单击退格键时，将检索数据。我只想自动检索扫描的标签并显示数据......

这是代码：

Private Sub Students_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
  loadtable()
  Timer2.Start()
End Sub

Private Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
  Dim StringIn As String = SerialPort1.ReadLine()
  Me.Invoke(Sub() studtag.Text = StringIn) 'we need to invoke since we're on another thread
End Sub

Private Sub studtag_TextChanged_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles studtag.TextChanged
  If studtag.TextLength = 8 Then
    con = New MySqlConnection
    con.ConnectionString = "server=localhost;userid=root;password=1234;database=dat"
    Dim query As String
    query = "select * from dat.students"
    cmd = New MySqlCommand(query, con)
    Dim table As New DataTable
    Try
      con.Open()
      'Gets or sets an SQL statement or stored procedure used to select records in the database.
      With cmd
        .Connection = con
        .CommandText = "SELECT * from students where `studtags`='" & studtag.Text & "';"
      End With
      da.SelectCommand = cmd
      da.Fill(table)
      'it gets the data from specific column and fill it into Label
      studtag.Text = table.Rows(0).Item(0)
      idno.Text = table.Rows(0).Item(1)
      lastxt.Text = table.Rows(0).Item(2)
      firstxt.Text = table.Rows(0).Item(3)
      middletxt.Text = table.Rows(0).Item(4)
      dob.Text = table.Rows(0).Item(6)
      agetxt.Text = table.Rows(0).Item(7)
      crsetxt.Text = table.Rows(0).Item(9)
      tagtxt.Text = studtag.Text
      timein.Text = times.Text
      dr = cmd.ExecuteReader()
      dr.Read()
      If dob.Text = datenow.Text Then
        greet.Text = "Happy Birthday To You"
      End If
      Dim img() As Byte = CType(dr("studpic"), Byte())
      Using ms As New IO.MemoryStream(img)
        PictureBox1.Image = Image.FromStream(ms)
      End Using
      insert()
      loadtable()
      Catch ex As Exception
        Notenrolled.Show()
      Finally
      con.Dispose()
      con.Close()
    End Try
  End If
End Sub

Public Sub insert()
  con = New MySqlConnection
  con.ConnectionString = "server=localhost;userid=root;password=1234;database=dat"
  Dim reader As MySqlDataReader
  Dim mstream As New System.IO.MemoryStream()
  Dim arrImage() As Byte = mstream.GetBuffer()
  mstream.Close()
  Try
    con.Open()
    Dim query3 As String
    query3 = "insert into dat.studlogs (studtags,idno,lastxt,firstxt,middletxt,dob,log,age,timein,crse,studpic) values ('" & tagtxt.Text & "','" & idno.Text & "','" & lastxt.Text & "','" & firstxt.Text & "','" & middletxt.Text & "','" & dob.Text & "','" & log.Text & "','" & agetxt.Text & "','" & timein.Text & "','" & crsetxt.Text & "',@studpic)"
    cmd = New MySqlCommand(query3, con)
    cmd.Parameters.AddWithValue("@studpic", arrImage)
    reader = cmd.ExecuteReader
    con.Close()
    Catch ex As Exception
      MessageBox.Show(ex.Message)
    Finally
      con.Dispose()
    End Try
  End Sub

  Public Sub loadtable()
    con = New MySqlConnection
    con.ConnectionString = "server=localhost;userid=root;password=1234;database=dat"
    Dim SDA As New MySqlDataAdapter
    Dim dbDataset As New DataTable
    Dim bSource As New BindingSource
    Try
      con.Open()
      Dim query3 As String
      query3 = "select studtags,idno,lastxt,firstxt,middletxt,dob,log,age,timein,crse from dat.studlogs"
      cmd = New MySqlCommand(query3, con)
      SDA.SelectCommand = cmd
      SDA.Fill(dbDataset)
      bSource.DataSource = dbDataset
      DataGridView1.DataSource = bSource
      SDA.Update(dbDataset)
      DataGridView1.Sort(DataGridView1.Columns(8), System.ComponentModel.ListSortDirection.Descending)
      con.Close()
      Catch ex As Exception
        MessageBox.Show(ex.Message)
      Finally
        con.Dispose()
      End Try
    End Sub

Arduino代码：

#include<SPI.h>
#include <MFRC522.h>

#define SS_PIN 10
#define RST_PIN 9

MFRC522 rfid(SS_PIN, RST_PIN); // Instance of the class
MFRC522::MIFARE_Key key;
// Init array that will store new NUID
byte nuidPICC[4];

void setup() {
  Serial.begin(9600);
  SPI.begin(); // Init SPI bus
  rfid.PCD_Init(); // Init MFRC522
  for (byte i = 0; i < 6; i++) {
    key.keyByte[i] = 0xFF;
  }
}

void loop() {
  // Look for new cards
  if (! rfid.PICC_IsNewCardPresent())
    return;
  // Verify if the NUID has been read
  if (! rfid.PICC_ReadCardSerial())
    return;
  for (byte i = 0; i < 4; i++) {
    nuidPICC[i] = rfid.uid.uidByte[i];
  }
  printHex(rfid.uid.uidByte, rfid.uid.size);
  Serial.println();
  rfid.PICC_HaltA();
  rfid.PCD_StopCrypto1();
}

void printHex(byte *buffer, byte bufferSize) {
  for (byte i = 0; i < bufferSize; i++) {
    Serial.print(buffer[i] < 0x10 ? "0":"");
    Serial.print(buffer[i], HEX);
  }
}

如您所见，从Arduino收到的数据必须是8位数或字符。例如，我在Arduino的串行监视器中的数据是7B6BA321。它匹配，所以过程开始。但是它无法检索数据......我需要在文本框中单击文本的末尾并单击退格键以进行检索。此外，当我单击退格键时，文本框中的8个字符的数据不会更改或删除最后一个字母或数字并进行检索。

我必须单击退格键两次以删除一个字母，如果我手动输入8个字符，它将从数据库中检索。我已经尝试过其他事件而不是textchanged而且我失败了。请帮我。如果您有任何问题，请随时发表评论。

我将提供截屏。

vb.net中的串口数据到文本框详细

0 个答案: