API调用打开文件对话框出现的问题
网上下载到的下面的API代码--用来调出选择文件的窗口。但是当我运行的时候，点击截图中的取消按钮时候，程序会报错退出，请问我应该怎么做？
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下面是类模块的代码
Option ExplicitPrivate Declare Function lstrlen Lib "kernel32" Alias "lstrlenA" (ByVal lpString As String) As LongPrivate Declare Function GlobalAlloc Lib "kernel32" (ByVal wFlags As Long, ByVal dwBytes As Long) As LongPrivate Declare Function GlobalCompact Lib "kernel32" (ByVal dwMinFree As Long) As LongPrivate Declare Function GlobalFree Lib "kernel32" (ByVal hMem As Long) As LongPrivate Declare Function GlobalLock Lib "kernel32" (ByVal hMem As Long) As LongPrivate Declare Function GlobalReAlloc Lib "kernel32" (ByVal hMem As Long, ByVal dwBytes As Long, ByVal wFlags As Long) As LongPrivate Declare Function GlobalSize Lib "kernel32" (ByVal hMem As Long) As LongPrivate Declare Function GlobalUnlock Lib "kernel32" (ByVal hMem As Long) As LongPrivate Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" ( _ lpvDest As Any, lpvSource As Any, ByVal cbCopy As Long)Private Declare Sub CopyMemoryStr Lib "kernel32" Alias "RtlMoveMemory" ( _ lpvDest As Any, ByVal lpvSource As String, ByVal cbCopy As Long) Private Const MAX_PATH = 32767Private Const MAX_FILE = 32767Private Type OpenFileName lStructSize As Long hWndOwner As Long hInstance As Long lpstrFilter As String lpstrCustomFilter As String nMaxCustFilter As Long nFilterIndex As Long lpstrFile As String nMaxFile As Long lpstrFileTitle As String nMaxFileTitle As Long lpstrInitialDir As String lpstrTitle As String flags As Long nFileOffset As Integer nFileExtension As Integer lpstrDefExt As String lCustData As Long lpfnHook As Long lpTemplateName As LongEnd TypePrivate Declare Function GetOpenFileName Lib "COMDLG32" _ Alias "GetOpenFileNameA" (file As OpenFileName) As LongPrivate Declare Function GetSaveFileName Lib "COMDLG32" _ Alias "GetSaveFileNameA" (file As OpenFileName) As LongPrivate Declare Function GetFileTitle Lib "COMDLG32" _ Alias "GetFileTitleA" (ByVal szFile As String, _ ByVal szTitle As String, ByVal cbBuf As Long) As LongPublic Enum EOpenFile OFN_READONLY = &H1 OFN_OVERWRITEPROMPT = &H2 OFN_HIDEREADONLY = &H4 OFN_NOCHANGEDIR = &H8 OFN_SHOWHELP = &H10 OFN_ENABLEHOOK = &H20 OFN_ENABLETEMPLATE = &H40 OFN_ENABLETEMPLATEHANDLE = &H80 OFN_NOVALIDATE = &H100 OFN_ALLOWMULTISELECT = &H200 OFN_EXTENSIONDIFFERENT = &H400 OFN_PATHMUSTEXIST = &H800 OFN_FILEMUSTEXIST = &H1000 OFN_CREATEPROMPT = &H2000 OFN_SHAREAWARE = &H4000 OFN_NOREADONLYRETURN = &H8000& OFN_NOTESTFILECREATE = &H10000 OFN_NONETWORKBUTTON = &H20000 OFN_NOLONGNAMES = &H40000 OFN_EXPLORER = &H80000 OFN_NODEREFERENCELINKS = &H100000 OFN_LONGNAMES = &H200000End EnumPrivate Const CCHDEVICENAME = 32Private Const CCHFORMNAME = 32 Private m_lApiReturn As LongPrivate m_lExtendedError As Long Public Property Get APIReturn() As Long APIReturn = m_lApiReturnEnd PropertyPublic Property Get ExtendedError() As Long ExtendedError = m_lExtendedErrorEnd Property#If fComponent ThenPrivate Sub Class_Initialize() InitColorsEnd Sub#End IfFunction VBGetOpenFileName(FileName As String, _ Optional FileTitle As String, _ Optional FileMustExist As Boolean = True, _ Optional MultiSelect As Boolean = False, _ Optional ReadOnly As Boolean = False, _ Optional HideReadOnly As Boolean = False, _ Optional Filter As String = "All (*.*)| *.*", _ Optional FilterIndex As Long = 1, _ Optional InitDir As String, _ Optional DlgTitle As String, _ Optional DefaultExt As String, _ Optional Owner As Long = -1, _ Optional flags As Long = 0) As Boolean Dim opfile As OpenFileName, S As String, afFlags As Long m_lApiReturn = 0 m_lExtendedError = 0With opfile .lStructSize = Len(opfile) .flags = (-FileMustExist * OFN_FILEMUSTEXIST) Or _ (-MultiSelect * OFN_ALLOWMULTISELECT) Or _ (-ReadOnly * OFN_READONLY) Or _ (-HideReadOnly * OFN_HIDEREADONLY) Or _ (flags And CLng(Not (OFN_ENABLEHOOK Or _ OFN_ENABLETEMPLATE))) If (.flags And OFN_ALLOWMULTISELECT) = OFN_ALLOWMULTISELECT Then .flags = .flags Or OFN_EXPLORER End If If Owner <> -1 Then .hWndOwner = Owner .lpstrInitialDir = InitDir .lpstrDefExt = DefaultExt .lpstrTitle = DlgTitle Dim ch As String, i As Integer For i = 1 To Len(Filter) ch = Mid$(Filter, i, 1) If ch = "|" Or ch = ":" Then S = S & vbNullChar Else S = S & ch End If Next ' Put double null at end S = S & vbNullChar & vbNullChar .lpstrFilter = S .nFilterIndex = FilterIndex ' Pad file and file title buffers to maximum path S = FileName & String$(MAX_PATH - Len(FileName), 0) .lpstrFile = S .nMaxFile = MAX_PATH S = FileTitle & String$(MAX_FILE - Len(FileTitle), 0) .lpstrFileTitle = S .nMaxFileTitle = MAX_FILE ' All other fields set to zero m_lApiReturn = GetOpenFileName(opfile) Select Case m_lApiReturn Case 1 ' Success VBGetOpenFileName = True If (.flags And OFN_ALLOWMULTISELECT) Then FileName = .lpstrFile Else FileName = StrZToStr(.lpstrFile) End If FileTitle = StrZToStr(.lpstrFileTitle) flags = .flags ' Return the filter index FilterIndex = .nFilterIndex ' Look up the filter the user selected and return that Filter = FilterLookup(.lpstrFilter, FilterIndex) If (.flags And OFN_READONLY) Then ReadOnly = True Case 0 ' Cancelled VBGetOpenFileName = False FileName = "" FileTitle = "" flags = 0 FilterIndex = -1 Filter = "" Case Else End SelectEnd WithEnd Function
