Question

你好我对vb有一点了解，所以请帮帮我。当我运行可以访问我的扫描仪的程序时，它有一个错误＆＃34; AccessViolationExeption未处理＆＃34; ＆＃34;尝试读取或写入受保护的内存。这通常表明其他内存已损坏。＆＃34;

这是我的代码：

   Public Sub CloseSource()
        Try
            Dim rc As TwRC
            If Not Equals(SelectedDataSource.Id, IntPtr.Zero) Then
                Dim guif As TwUserInterface = New TwUserInterface()

                ' tell the data source to disable its user interface
                rc = DS_Userif(appid, SelectedDataSource, TwDG.TwDG_Control, TwDAT.TwDAT_UserInterface, TwMSG.TwMSG_DisableDS, guif)

                ' tell the device manager to release the source
                rc = DSM_Ident(appid, IntPtr.Zero, TwDG.TwDG_Control, TwDAT.TwDAT_Identity, TwMSG.TwMSG_CloseDS, SelectedDataSource)

                ' set the pointer to zero
                SelectedDataSource.Id = IntPtr.Zero
            End If
        Catch ex As Exception

        End Try

    End Sub

Answer 1

<StructLayout(LayoutKind.Sequential, Pack:=2)> Public Class TW_USERINTERFACE
    Public ShowUI As Short ' TW_BOOL
    Public ModalUI As Short ' TW_BOOL
    Public hParent As UInt32 ' TW_HANDLE
End Class

不幸的是，bool是4bytes 所以我们使用short（0 = false 1 = true）

Answer 2

从您的消息和代码中我了解到，关闭扫描仪时会出现异常。我认为你有例外，因为扫描仪还没有准备好关闭。请确保扫描仪处于正确状态并可以关闭。

此致，亚历山大

Visual Basic与Twain应用程序

2 个答案: