我已将C＃代码转换为VB.net并已应用所需的小调整。
但是当我测试代码时，它会在这些指令的位置产生错误：
If Not capture.Cued Then
capture.Filename = counter & ".wmv"
我不是DirectShow的专家，我需要该代码继续学习。请有人能给我慷慨的帮助吗？
我将不胜感激任何帮助。谢谢。
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Linq
Imports System.Text
Imports System.Windows.Forms
Imports DirectX.Capture
Imports DShowNET
Public Class MyWebCam
Inherits Form
' Muaz Khan (@muazkh) - http://muaz-khan.blogspot.com
Private capture As Capture = Nothing
Private filters As Filters = Nothing
Private counter As Integer = 1
Private timer As New Timer()
Private deviceNumber As Integer = 0
Public Sub New()
InitializeComponent()
End Sub
'============================================================================
Private Sub Form1_Shown(sender As Object, e As EventArgs)
filters = New Filters()
If filters.VideoInputDevices IsNot Nothing Then
Try
preview(deviceNumber)
Catch ex As Exception
MessageBox.Show("Maybe any other software is already using your WebCam." & vbLf & vbLf & " Error Message: " & vbLf & vbLf & ex.Message)
End Try
Else
btnStartVideoCapture.Enabled = False
MessageBox.Show("No video device connected to your PC!")
End If
timer.Interval = 600000
' 10 minutes!
AddHandler timer.Tick, Function(obj, evt)
If btnStartVideoCapture.Text = "STOP" Then
counter += 1
If capture IsNot Nothing AndAlso counter > 1 Then
capture.[Stop]()
If Not capture.Cued Then
capture.Filename = counter & ".wmv"
End If
capture.Cue()
capture.Start()
End If
End If
End Function
If filters.VideoInputDevices IsNot Nothing Then
For i = 0 To filters.VideoInputDevices.Count - 1
Dim device = filters.VideoInputDevices(i)
Dim btn = New Button()
btn.Text = i.ToString()
btn.ForeColor = Color.White
btn.BackColor = Color.DarkSlateBlue
btn.Width = 25
AddHandler btn.Click, Function(obj, evt)
Dim thisButton = DirectCast(obj, Button)
If Integer.Parse(thisButton.Text) <> deviceNumber Then
If capture IsNot Nothing Then
capture.Dispose()
capture.[Stop]()
capture.PreviewWindow = Nothing
End If
deviceNumber = Integer.Parse(thisButton.Text)
preview(deviceNumber)
End If
End Function
FlowLayoutPanel1.Controls.Add(btn)
Next
End If
End Sub
'============================================================================
Private Sub preview(deviceNo As Integer)
Try
' MessageBox.Show("deviceNo = > " + deviceNo);
capture = New Capture(filters.VideoInputDevices(deviceNo), filters.AudioInputDevices(0))
capture.PreviewWindow = Panel1
If btnStartVideoCapture.Text = "STOP" Then
counter += 1
If Not capture.Cued Then
capture.Filename = counter & ".wmv"
End If
capture.Cue()
End If
capture.Start()
Catch
End Try
End Sub
'============================================================================
Private Sub btnStartVideoCapture_Click(sender As System.Object, e As System.EventArgs) Handles btnStartVideoCapture.Click
startOrStopCapturing(capture)
End Sub
'============================================================================
Private Sub startOrStopCapturing(capture As Capture)
btnStartVideoCapture.Visible = False
'**** THE ERROR BEGINS TO APPEAR HERE ************
'****
'****
If capture IsNot Nothing Then
capture.[Stop]()
End If
If timer.Enabled Then
timer.[Stop]()
End If
If btnStartVideoCapture.Text = "START" Then
btnStartVideoCapture.Text = "STOP"
btnStartVideoCapture.BackColor = Color.Maroon
Try
If Not capture.Cued Then
capture.Filename = counter & ".wmv"
End If
capture.Cue()
capture.Start()
timer.Start()
Catch ex As Exception
MessageBox.Show("Error Message: " & vbLf & vbLf & ex.Message)
End Try
Else
btnStartVideoCapture.Text = "START"
btnStartVideoCapture.BackColor = Color.DarkSlateBlue
End If
btnStartVideoCapture.Visible = True
End Sub
'============================================================================
Private Sub InitializeComponent()
Me.btnStartVideoCapture = New System.Windows.Forms.Button()
Me.FlowLayoutPanel1 = New System.Windows.Forms.FlowLayoutPanel()
Me.Panel1 = New System.Windows.Forms.Panel()
Me.SuspendLayout()
'
'btnStartVideoCapture
'
Me.btnStartVideoCapture.BackColor = System.Drawing.Color.DarkSlateBlue
Me.btnStartVideoCapture.Font = New System.Drawing.Font("Microsoft Sans Serif", 9.75!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.btnStartVideoCapture.ForeColor = System.Drawing.Color.White
Me.btnStartVideoCapture.Location = New System.Drawing.Point(498, 421)
Me.btnStartVideoCapture.Name = "btnStartVideoCapture"
Me.btnStartVideoCapture.Size = New System.Drawing.Size(89, 38)
Me.btnStartVideoCapture.TabIndex = 2
Me.btnStartVideoCapture.Text = "START"
Me.btnStartVideoCapture.UseVisualStyleBackColor = False
'
'FlowLayoutPanel1
'
Me.FlowLayoutPanel1.Location = New System.Drawing.Point(0, 421)
Me.FlowLayoutPanel1.Name = "FlowLayoutPanel1"
Me.FlowLayoutPanel1.Size = New System.Drawing.Size(502, 38)
Me.FlowLayoutPanel1.TabIndex = 3
'
'Panel1
'
Me.Panel1.Location = New System.Drawing.Point(0, -3)
Me.Panel1.Name = "Panel1"
Me.Panel1.Size = New System.Drawing.Size(587, 418)
Me.Panel1.TabIndex = 4
'
'Form1
'
Me.BackColor = System.Drawing.Color.Black
Me.ClientSize = New System.Drawing.Size(585, 458)
Me.Controls.Add(Me.Panel1)
Me.Controls.Add(Me.FlowLayoutPanel1)
Me.Controls.Add(Me.btnStartVideoCapture)
Me.Name = "Form1"
Me.ResumeLayout(False)
End Sub
Private WithEvents btnStartVideoCapture As System.Windows.Forms.Button
Friend WithEvents FlowLayoutPanel1 As System.Windows.Forms.FlowLayoutPanel
Friend WithEvents Panel1 As System.Windows.Forms.Panel
End Class
答案 0 :(得分：1)
在startStopCapturing中，您无法检查capture IsNothing 。当您在preview形式事件或计时器事件中输入Shown方法时，将初始化捕获对象。
你到处都有代码来检查IsNothing的捕获对象并避免使用它，但在startStopCapturing中，你没有这个检查来保护改变按钮文本的IF中的代码。
Private Sub startOrStopCapturing(capture As Capture)
btnStartVideoCapture.Visible = False
If capture IsNot Nothing Then
capture.[Stop]()
capture.Dispose()
capture = Nothing
If timer.Enabled Then
timer.[Stop]()
End If
btnStartVideoCapture.Text = "START"
btnStartVideoCapture.BackColor = Color.DarkSlateBlue
Else
Try
capture = New Capture(filters.VideoInputDevices(deviceNumber), _
filters.AudioInputDevices(0))
capture.Filename = counter & ".wmv"
capture.Cue()
capture.Start()
timer.Start()
btnStartVideoCapture.Text = "STOP"
btnStartVideoCapture.BackColor = Color.Maroon
Catch ex As Exception
MessageBox.Show("Error Message: " & vbLf & vbLf & ex.Message)
End Try
End If
btnStartVideoCapture.Visible = True
End Sub
此外，内联button_click事件中的代码似乎是错误的
If capture IsNot Nothing Then
capture.Dispose()
capture.[Stop]()
capture.PreviewWindow = Nothing
End iF
不要使用已处置的对象并将其设置为Nothing，因为如果没有它，您可以再次欺骗您的代码以确保捕获对象有效
If capture IsNot Nothing Then
capture.[Stop]()
capture.PreviewWindow = Nothing
capture.Dispose()
capture = Nothing
End iF