c++ - 从 CFileDialog 调用时，IFileOpenDialog 指针为空

Question

我试图将 CFileDialog 和 IFileOpenDialog 包装在一个类中，这是代码:

class ITest
{
    public:
    virtual ~ITest(){};

    virtual INT_PTR DoModal() = 0;

    virtual IFileOpenDialog* GetDlg() = 0;
};

class test : public ITest
{
public:
   test(BOOL bOpenFileDialog, // TRUE for FileOpen, FALSE for FileSaveAs
       LPCTSTR lpszDefExt = NULL,
       LPCTSTR lpszFileName = NULL,
       DWORD dwFlags = OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT,
       LPCTSTR lpszFilter = NULL,
       CWnd* pParentWnd = NULL,
       DWORD dwSize = 0,
       BOOL bVistaStyle = FALSE)
   {
       dlg = new CFileDialog(bOpenFileDialog, lpszDefExt, lpszFileName, dwFlags, lpszFilter, pParentWnd, dwSize, bVistaStyle);
   };
   ~test(){};

   INT_PTR DoModal(){ return S_OK; };

   IFileOpenDialog* GetDlg(){ return dlg->GetIFileOpenDialog(); };
private:
   CFileDialog* dlg;
};

然后当我这样调用它时:

ITest* a = new test(TRUE, NULL, 0, OFN_ALLOWMULTISELECT | OFN_NOVALIDATE, LoadResourceString(IDS_MYSTRING), this);

fdlg = a->GetDlg();

fdlg->Show(NULL);//it crashes here since fdlg is NULL

然后我尝试直接调用CFileDialog 和IFileOpenDialog:

IFileOpenDialog* fdlg = NULL;

CFileDialog* b = new CFileDialog(TRUE, NULL, 0, OFN_ALLOWMULTISELECT | OFN_NOVALIDATE, LoadResourceString(IDS_MYSTRING), this);

fdlg = b->GetIFileOpenDialog();

fdlg->Show(NULL);

这部分代码完美运行。任何人都知道为什么会发生崩溃？这让我很困惑，因为我觉得它们是如此相似。

class test : public ITest
{
public:
test(BOOL bOpenFileDialog, // TRUE for FileOpen, FALSE for FileSaveAs
    LPCTSTR lpszDefExt = NULL,
    LPCTSTR lpszFileName = NULL,
    DWORD dwFlags = OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT,
    LPCTSTR lpszFilter = NULL,
    CWnd* pParentWnd = NULL,
    DWORD dwSize = 0,
    BOOL bVistaStyle = FALSE)
{
    dlg = new CFileDialog(bOpenFileDialog, lpszDefExt, lpszFileName, dwFlags, lpszFilter, pParentWnd, dwSize, bVistaStyle);
};
~test(){};

INT_PTR DoModal(){ return S_OK; };

IFileOpenDialog* GetDlg();
private:
CFileDialog* dlg;
};

IFileOpenDialog* test::GetDlg()
{ 
return dlg->GetIFileOpenDialog(); 
};

上面的代码也不起作用(它在类声明之外定义了 IFileOpenDialog* GetDlg();)

Answer 1

来自help :

Use this function only under Windows Vista with an object that has bVistaStyle set to true. This function returns NULL if the CFileDialog is not an Open dialog box or if bVistaStyle is set to false.

当您构建测试 对象时:

ITest* a = new test(TRUE, NULL, 0, OFN_ALLOWMULTISELECT | OFN_NOVALIDATE, LoadResourceString(IDS_MYSTRING), this);

您要离开构造函数的最后一个参数 bVistaStyle，它默认为 FALSE。所以只需添加它:

ITest* a = new test(TRUE, NULL, 0, OFN_ALLOWMULTISELECT | OFN_NOVALIDATE, LoadResourceString(IDS_MYSTRING), this, 0, 
               TRUE); // bVistaStyle