Question

首先是一些背景信息：此应用程序的目的是捕获图像并将其自动保存到网络目录中，该目录将使用文本框的输入创建或附加。这段代码可以在我的电脑上运行（Windows 7家64位）。我使用microsoft visual basic express 2010创建了它。

然而.....当试图在Windows 10平板电脑上运行应用程序时，我收到以下错误：

表单加载：

An error occurred while capturing the image.  The video capture will now be terminated.

Object reference not set to an instance of an object.

按钮2_点击事件：

Object reference not set to an instance of an object.

以下是整个代码。

Form2.vb

Public Class Form2
    Public scanIsSet As Boolean
    Private webcam As WebCam
    Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        webcam = New WebCam()
        webcam.InitializeWebCam(imgVideo)
        webcam.Start()
        scanIsSet = False
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim CFGfile As String
        Dim SaveDir As String
        Dim imgIndex As Integer
        Dim existingImages() As String
        SaveDir = "C:\somepath\"


            'save image to directory with index number
            Try
                imgCapture.Image.Save(SaveDir & OrderNumber.Text & "\" & CStr(imgIndex) & ".jpg")
            Catch ex As Exception
                MsgBox("error while accessing object imgCapture" & ex.Message)
            End Try
            imgIndex = imgIndex + 1

        Else
            Beep()
            MsgBox("Please scan or type in order number first")
        End If
    End Sub
End Class

WebCam.vb

Imports System
Imports System.IO
Imports System.Linq
Imports System.Text
Imports WebCam_Capture
Imports System.Collections.Generic
Imports ZXing
Imports ZXing.OneD

'Design by Pongsakorn Poosankam
Class WebCam
    Public scanz As Boolean
    Public Sub setScan(ByVal x As Boolean)
        scanz = x
    End Sub
    Private webcam As WebCamCapture
    Private _FrameImage As System.Windows.Forms.PictureBox
    Private FrameNumber As Integer = 30
    Public Sub InitializeWebCam(ByRef ImageControl As System.Windows.Forms.PictureBox)
        webcam = New WebCamCapture()
        webcam.FrameNumber = CULng((0))
        webcam.TimeToCapture_milliseconds = FrameNumber
        AddHandler webcam.ImageCaptured, AddressOf webcam_ImageCaptured
        _FrameImage = ImageControl
    End Sub

    Private Sub webcam_ImageCaptured(ByVal source As Object, ByVal e As WebcamEventArgs)
        _FrameImage.Image = e.WebCamImage
        If scanz = True Then
            Dim BCreader As New ZXing.BarcodeReader

            'BCreader.Options.TryHarder = True
            Try
                Dim resu As Result = BCreader.Decode(e.WebCamImage)

                Form2.OrderNumber.Text = resu.Text
                setScan(False)
                Form2.Label2.Text = ""
                Beep()
            Catch ex As Exception
                'do nothing
            End Try
        End If
    End Sub

    Public Sub Start()
        webcam.TimeToCapture_milliseconds = FrameNumber
        webcam.Start(0)
    End Sub

    Public Sub [Stop]()
        webcam.[Stop]()
    End Sub

    Public Sub [Continue]()
        ' change the capture time frame
        webcam.TimeToCapture_milliseconds = FrameNumber

        ' resume the video capture from the stop
        webcam.Start(Me.webcam.FrameNumber)
    End Sub

    Public Sub ResolutionSetting()
        webcam.Config()
    End Sub

    Public Sub AdvanceSetting()
        webcam.Config2()
    End Sub

End Class

正如您在 Form2.vb 结束时所看到的，我已将imgCapture.Image.Save(SaveDir & OrderNumber.Text & "\" & CStr(imgIndex) & ".jpg")包装在Try-Catch块中，因为我怀疑它是pictureBox对象的某些问题。 try catch块确实捕获了异常，但我仍然不知道问题是什么，为什么它发生在平板电脑而不是PC上，或者如何解决它。

我发现了类似的问题，但没有找到我可以使用的解决方案。

Answer 1

由于你使用的是EasyWebCam，它过时且与Win10不兼容，我建议切换库。其他选择：

DirectX.Capture
Windows.Media.Capture

Answer 2

我找到了解决方案，但我不知道您现在是否需要它，问题是如果您更改了 PICTUREBOX 名称，则作为参考使用您已更改的确切名称。例如，如果我将所有 PICTUREBOX 名称更改为 -

PictureBox_A1 , PictureBox_A2 ,... 等等然后我的参考应该是 -

Dim r As DataRow

        For Each r In t1.Rows
            CType(Controls("PictureBox_" & r(2)), PictureBox).Image = bookedicon
        Next

我的参考是 - “PictureBox_”

对象引用未设置为对象的实例 - vb.net

2 个答案: