vb.net - 如何在 VB 中加载窗体窗口后运行函数/子？

Question

我有一个从 USB 徽章读取器获取用户 ID 的功能，用于登录应用程序。当我运行该应用程序时，在我滑动标签之前不会出现登录窗口。我需要知道是否可以加载窗口，然后开始运行从 USB 获取数据的函数。

谢谢:)

Private Sub SerialPort1_DataReceived()
    'Threading.Thread.SpinWait(1000)
    OpenPort()
    If SerialPort1.IsOpen() Then

        byteEnd = SerialPort1.NewLine.ToCharArray
        'read entire string until .Newline 
        readBuffer = SerialPort1.ReadLine()
        readBuffer = readBuffer.Remove(0, 1)
        readBuffer = readBuffer.Remove(8, 1)
        WWIDTextBox.AppendText(readBuffer)

    End If
End Sub

Private Sub Form1_Activated(ByVal sender As Object, _
ByVal e As System.EventArgs) Handles MyBase.Activated
    SerialPort1_DataReceived()
End Sub

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    'SerialPort1_DataReceived()
End Sub

Answer 1

问题是您正在调用 ReadLine 方法，这是一个阻塞(同步)方法。换句话说，当您调用它时，该方法只有在具有要返回的值后才会返回值。因此，它会停止在当前线程上执行，直到读取完整的一行(当徽章被刷过时)。由于您在调用它时处于 UI 线程上，因此它会锁定 UI，直到徽章被刷过。

无需从 UI 线程调用 SerialPort1_DataReceived 方法，您可以从不同的线程完成这项工作。最简单的方法是将 BackgroundWorker 组件拖到设计器中的窗体上。然后你可以添加这样的代码:

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    BackgroundWorker1.RunWorkerAsync()
End Sub

Private Sub BackgroundWorker1_DoWork(sender As Object, e As DoWorkEventArgs) Handles BackgroundWorker1.DoWork
    OpenPort()
    If SerialPort1.IsOpen() Then
        byteEnd = SerialPort1.NewLine.ToCharArray
        Dim readBuffer As String = SerialPort1.ReadLine()
        readBuffer = readBuffer.Remove(0, 1)
        readBuffer = readBuffer.Remove(8, 1)
        e.Result = readBuffer
    End If
End Sub

Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
    WWIDTextBox.AppendText(CStr(e.Result))
End Sub