打开文件对话框在xp和win7上的实现文件任意多选

作者：朱金灿

来源：http://blog.csdn.net/clever101

在xp系统上进行文件多选，实际上其文件字符串数组的缓冲区是有限，并不能支持选择任意多个文件，为此以前我还写过一篇文章：使用CFileDialog的钩子函数解决对话框的多选问题。实际上这种做法在vista系统及win7系统上并不支持。那么如何在vista系统及win7系统支持打开文件对话框任意多选文件呢？我想到windows是一个基于com的系统，没准使用com接口能做到。事实上是这样的，需要使用一个叫IFileOpenDialog的接口类。下面是示例代码：

// Return the file system path for a given IShellItem.
static bool PathFromShellItem ( IShellItem* pItem, CString& sPath )
{
HRESULT hr;
LPOLESTR pwsz = NULL;

hr = pItem->GetDisplayName ( SIGDN_FILESYSPATH, &pwsz );

if ( FAILED(hr) )
return false;

sPath = pwsz;
CoTaskMemFree ( pwsz );
return true;
}

// Convert a pipe-separated list of filter strings into a vector of
// COMDLG_FILTERSPEC. The vector<CString> is needed to actually hold the strings
// that the COMDLG_FILTERSPEC structs will point to.
static bool BuildFilterSpecList (_U_STRINGorID szFilterList,
COMDLG_FILTERSPEC*& pVecFilter,int& nFilterNum )
{
std::vector<CString> vecsFilterParts;
CString sFilterList = szFilterList.m_lpstr;
CString sToken;
int nIdx = 0;

// Split the passed-in filter list on pipe characters (MFC-style)
for(;;)
{
sToken = sFilterList.Tokenize(_T("|"), nIdx );
if ( sToken.IsEmpty() )
break;

vecsFilterParts.push_back ( sToken );
}

// There should be an even number of tokens in the string
if ( vecsFilterParts.size() & 1 )
{
ATLASSERT(0);
vecsFilterParts.pop_back();
}

if(vecsFilterParts.empty())
return false;

nFilterNum = vecsFilterParts.size()/2.0;
pVecFilter = new COMDLG_FILTERSPEC[nFilterNum];

// Use each pair of tokens for a COMDLG_FILTERSPEC struct.
/*for (std::vector<CString>::size_type i = 0; i < vecsFilterParts.size(); i += 2 )*/
for (std::vector<CString>::size_type i = 0; i <nFilterNum; i++)
{
USES_CONVERSION;

int j = i*2;

std::wstring strName = A2W(vecsFilterParts[j]);
pVecFilter[i].pszName = new WCHAR[strName.length()+1];
memset((void*)pVecFilter[i].pszName,'\0',(strName.length()+1)*sizeof(WCHAR));
wcsncpy((wchar_t*)pVecFilter[i].pszName,strName.c_str(),strName.length());

j = j+1;
std::wstring strSpec = A2W(vecsFilterParts[j]);
pVecFilter[i].pszSpec = new WCHAR[strSpec.length()+1];
memset((void*)pVecFilter[i].pszSpec,'\0',(strSpec.length()+1)*sizeof(WCHAR));
wcsncpy((wchar_t*)pVecFilter[i].pszSpec,strSpec.c_str(),strSpec.length());
}
//	return !vecFilters.empty();
return true;
}

void CMultiSelectDlg::OnBnClickedBtnVista()
{
// TODO: 在此添加控件通知处理程序代码
HRESULT hr;
CComPtr<IFileOpenDialog> pDlg;
//	std::vector<CString> vecsFilterParts;
//	std::vector<COMDLG_FILTERSPEC> vecFilters;

COMDLG_FILTERSPEC* pVecFilter = NULL;;
int nFilterNum = 0;

//	std::vector<std::wstring> vecFilters;

CString sDlgTitle = _T("Multi-selection File Open Dialog");
CString sOKButtonLabel = _T("确定");
CString sFilenameLabel = _T("文件名(N):");
DWORD dwFlags = 0;

// Create the file-open dialog COM object.
hr = pDlg.CoCreateInstance( __uuidof(FileOpenDialog) );

if ( FAILED(hr) )
return;

// Tell the dlg to load the state data associated with this GUID:
// {7D5FE367-E148-4a96-B326-42EF237A3662}
// This is not strictly necessary for our app (normally you'd wand loads
// and saves to share the same state data) but I'm putting this in for the demo.
static const GUID guidFileOpen = { 0x7D5FE367, 0xE148, 0x4A96, { 0xB3, 0x26, 0x42, 0xEF, 0x23, 0x7A, 0x36, 0x62 } };

hr = pDlg->SetClientGuid ( guidFileOpen );

// Call this helper function to convert a pipe-separated file spec list
// (like MFC uses) to a vector of COMDLG_FILTERSPEC.
if ( BuildFilterSpecList(_T("Text files (*.txt)|*.txt|Executable files (*.exe;*.dll)|*.exe;*.dll|All files (*.*)|*.*|"),
pVecFilter,nFilterNum))
hr = pDlg->SetFileTypes(nFilterNum,pVecFilter);

// Set some other properties of the dialog. It's not the end of the world if
// any of these calls fail.
USES_CONVERSION;
hr = pDlg->SetTitle (A2W(sDlgTitle));
hr = pDlg->SetOkButtonLabel(A2W(sOKButtonLabel));
hr = pDlg->SetFileNameLabel(A2W(sFilenameLabel));

// Set the multi-select option flag.
hr = pDlg->GetOptions ( &dwFlags );
hr = pDlg->SetOptions ( dwFlags | FOS_ALLOWMULTISELECT );

// Set up our event listener.
//	CComObjectStackEx<CDlgEventHandler> cbk;

// Show the dialog!
hr = pDlg->Show ( m_hWnd );

//if ( bAdvised )
//	pDlg->Unadvise ( dwCookie );

// Get the list of selected items and add each filename to the list ctrl.
if ( SUCCEEDED(hr) )
{
CComPtr<IShellItemArray> pItemArray;

hr = pDlg->GetResults ( &pItemArray );

if ( SUCCEEDED(hr) )
{
DWORD cSelItems;
hr = pItemArray->GetCount ( &cSelItems );

if ( SUCCEEDED(hr) )
{
int nCount = 0;
for ( DWORD j = 0; j < cSelItems; j++ )
{
CComPtr<IShellItem> pItem;
hr = pItemArray->GetItemAt ( j, &pItem );
if ( SUCCEEDED(hr) )
{
CString sPath;
if ( PathFromShellItem ( pItem, sPath ) )
{
m_listbox.AddString(sPath);
nCount++;
}
}
}
CString str;
str.Format(_T("%u files selected"), nCount);
m_static.SetWindowText(str);
}
}
}

for (int i  = 0;i<nFilterNum;i++)
{
delete []pVecFilter[i].pszName;
delete []pVecFilter[i].pszSpec;
}
delete []pVecFilter;
}

值得注意的是这个做法并不兼容xp系统，因此在使用哪种做法时需要你先对操作系统的版本进行判断。我专门写了一个例程供大家参考：VC文件多选对话框

参考文献：

1. WindowsVista for Developers——第六部分：新的文件对话框

2. IFileDialog使用指南