LNK2019 示例来自 MSDN

Question

试图从 Common File Dialog Sample got some LNK2019 中的 .cpp 文件复制代码。链接 3 个函数似乎有问题。以下是错误：

Severity    Code    Description Project File    Line    Suppression State
Error   LNK2019 unresolved external symbol __imp_TaskDialog referenced in function "public: class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __cdecl CDialogEventHandler::ChooseFromFolder(void)" (?ChooseFromFolder@CDialogEventHandler@@QEAA?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@XZ)    Build-A-Font    C:\Users\nadav\Desktop\SFML\Build-A-Font\Build-A-Font\FileDialog.obj    1   
Error   LNK2019 unresolved external symbol __imp_PSGetPropertyDescriptionListFromString referenced in function "public: virtual long __cdecl CDialogEventHandler::OnTypeChange(struct IFileDialog *)" (?OnTypeChange@CDialogEventHandler@@UEAAJPEAUIFileDialog@@@Z) Build-A-Font    C:\Users\nadav\Desktop\SFML\Build-A-Font\Build-A-Font\FileDialog.obj    1   
Error   LNK2019 unresolved external symbol QISearch referenced in function "public: virtual long __cdecl CDialogEventHandler::QueryInterface(struct _GUID const &,void * *)" (?QueryInterface@CDialogEventHandler@@UEAAJAEBU_GUID@@PEAPEAX@Z)   Build-A-Font    C:\Users\nadav\Desktop\SFML\Build-A-Font\Build-A-Font\FileDialog.obj    1

这是他们根据我的需要修改后的代码：

#pragma once
#define STRICT_TYPED_ITEMIDS
#include <shlobj.h>
#include <shlwapi.h>
#include <string>
#include <sstream>

#pragma comment(linker, "\"/manifestdependency:type='Win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' processorArchitecture='*' publicKeyToken='6595b64144ccf1df' language='*'\"")
// Added for changing the entry point
#pragma comment(linker, "/subsystem:windows /ENTRY:mainCRTStartup")

const COMDLG_FILTERSPEC c_rgSaveTypes[] =
{
    {L"Word Document (*.doc; *.docx)",  L"*.doc;*.docx"},
    {L"Powerpoint Presentation (*.ppt; *.pptx)",  L"*.ppt;*.pptx"},
    {L"Web Page (*.htm; *.html)",       L"*.htm;*.html"},
    {L"Text Document (*.txt)",          L"*.txt"},
    {L"All Documents (*.*)",            L"*.*"}
};

// Indices of file types
#define INDEX_WORDDOC 1
#define INDEX_PRPNTPR 2
#define INDEX_WEBPAGE 3
#define INDEX_TEXTDOC 4

// Controls
#define CONTROL_GROUP           2000
#define CONTROL_RADIOBUTTONLIST 2
#define CONTROL_RADIOBUTTON1    1
#define CONTROL_RADIOBUTTON2    2       // It is OK for this to have the same ID as CONTROL_RADIOBUTTONLIST,
                                        // because it is a child control under CONTROL_RADIOBUTTONLIST

// IDs for the Task Dialog Buttons
#define IDC_BASICFILEOPEN                       100

/* File Dialog Event Handler *****************************************************************************************************/

class CDialogEventHandler : public IFileDialogEvents,
    public IFileDialogControlEvents
{
public:
    // IUnknown methods
    IFACEMETHODIMP QueryInterface(REFIID riid, void** ppv)
    {
        static const QITAB qit[] = {
            QITABENT(CDialogEventHandler, IFileDialogEvents),
            QITABENT(CDialogEventHandler, IFileDialogControlEvents),
            { 0 },
#pragma warning(suppress:4838)
        };
        return QISearch(this, qit, riid, ppv);
    }

    IFACEMETHODIMP_(ULONG) AddRef()
    {
        return InterlockedIncrement(&_cRef);
    }

    IFACEMETHODIMP_(ULONG) Release()
    {
        long cRef = InterlockedDecrement(&_cRef);
        if (!cRef)
            delete this;
        return cRef;
    }

    // IFileDialogEvents methods
    IFACEMETHODIMP OnFileOk(IFileDialog*) { return S_OK; };
    IFACEMETHODIMP OnFolderChange(IFileDialog*) { return S_OK; };
    IFACEMETHODIMP OnFolderChanging(IFileDialog*, IShellItem*) { return S_OK; };
    IFACEMETHODIMP OnHelp(IFileDialog*) { return S_OK; };
    IFACEMETHODIMP OnSelectionChange(IFileDialog*) { return S_OK; };
    IFACEMETHODIMP OnShareViolation(IFileDialog*, IShellItem*, FDE_SHAREVIOLATION_RESPONSE*) { return S_OK; };
    IFACEMETHODIMP OnOverwrite(IFileDialog*, IShellItem*, FDE_OVERWRITE_RESPONSE*) { return S_OK; };
    // This method gets called when the file-type is changed (combo-box selection changes).
    // For sample sake, let's react to this event by changing the properties show.
    IFACEMETHODIMP OnTypeChange(IFileDialog* pfd)
    {
        IFileSaveDialog* pfsd;
        HRESULT hr = pfd->QueryInterface(&pfsd);
        if (SUCCEEDED(hr))
        {
            UINT uIndex;
            hr = pfsd->GetFileTypeIndex(&uIndex);   // index of current file-type
            if (SUCCEEDED(hr))
            {
                IPropertyDescriptionList* pdl = NULL;

                switch (uIndex)
                {
                case INDEX_WORDDOC:
                    // When .doc is selected, let's ask for some arbitrary property, say Title.
                    hr = PSGetPropertyDescriptionListFromString(L"prop:System.Title", IID_PPV_ARGS(&pdl));
                    if (SUCCEEDED(hr))
                    {
                        // FALSE as second param == do not show default properties.
                        hr = pfsd->SetCollectedProperties(pdl, FALSE);
                        pdl->Release();
                    }
                    break;

                case INDEX_WEBPAGE:
                    // When .html is selected, let's ask for some other arbitrary property, say Keywords.
                    hr = PSGetPropertyDescriptionListFromString(L"prop:System.Keywords", IID_PPV_ARGS(&pdl));
                    if (SUCCEEDED(hr))
                    {
                        // FALSE as second param == do not show default properties.
                        hr = pfsd->SetCollectedProperties(pdl, FALSE);
                        pdl->Release();
                    }
                    break;

                case INDEX_TEXTDOC:
                    // When .txt is selected, let's ask for some other arbitrary property, say Author.
                    hr = PSGetPropertyDescriptionListFromString(L"prop:System.Author", IID_PPV_ARGS(&pdl));
                    if (SUCCEEDED(hr))
                    {
                        // TRUE as second param == show default properties as well, but show Author property first in list.
                        hr = pfsd->SetCollectedProperties(pdl, TRUE);
                        pdl->Release();
                    }
                    break;
                }
            }
            pfsd->Release();
        }
        return hr;
    };
    // IFileDialogControlEvents methods

    // This method gets called when an dialog control item selection happens (radio-button selection. etc).
    // For sample sake, let's react to this event by changing the dialog title.
    IFACEMETHODIMP OnItemSelected(IFileDialogCustomize* pfdc, DWORD dwIDCtl, DWORD dwIDItem)
    {
        IFileDialog* pfd = NULL;
        HRESULT hr = pfdc->QueryInterface(&pfd);
        if (SUCCEEDED(hr))
        {
            if (dwIDCtl == CONTROL_RADIOBUTTONLIST)
            {
                switch (dwIDItem)
                {
                case CONTROL_RADIOBUTTON1:
                    hr = pfd->SetTitle(L"Longhorn Dialog");
                    break;

                case CONTROL_RADIOBUTTON2:
                    hr = pfd->SetTitle(L"Vista Dialog");
                    break;
                }
            }
            pfd->Release();
        }
        return hr;
    };
    IFACEMETHODIMP OnButtonClicked(IFileDialogCustomize*, DWORD) { return S_OK; };
    IFACEMETHODIMP OnCheckButtonToggled(IFileDialogCustomize*, DWORD, BOOL) { return S_OK; };
    IFACEMETHODIMP OnControlActivating(IFileDialogCustomize*, DWORD) { return S_OK; };

    CDialogEventHandler() : _cRef(1) { };
private:
    ~CDialogEventHandler() { };
    long _cRef;
};

// Instance creation helper
HRESULT CDialogEventHandler_CreateInstance(REFIID riid, void** ppv)
{
    *ppv = NULL;
    CDialogEventHandler* pDialogEventHandler = new (std::nothrow) CDialogEventHandler();
    HRESULT hr = pDialogEventHandler ? S_OK : E_OUTOFMEMORY;
    if (SUCCEEDED(hr))
    {
        hr = pDialogEventHandler->QueryInterface(riid, ppv);
        pDialogEventHandler->Release();
    }
    return hr;
}

// This code snippet demonstrates how to work with the common file dialog interface
std::string BasicFileOpen()
{
    // CoCreate the File Open Dialog object.
    IFileDialog* pfd = NULL;
    HRESULT hr = CoCreateInstance(CLSID_FileOpenDialog, NULL, CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&pfd));
    if (SUCCEEDED(hr))
    {
        // Create an event handling object, and hook it up to the dialog.
        IFileDialogEvents* pfde = NULL;
        hr = CDialogEventHandler_CreateInstance(IID_PPV_ARGS(&pfde));
        if (SUCCEEDED(hr))
        {
            // Hook up the event handler.
            DWORD dwCookie;
            hr = pfd->Advise(pfde, &dwCookie);
            if (SUCCEEDED(hr))
            {
                // Set the options on the dialog.
                DWORD dwFlags;

                // Before setting, always get the options first in order not to override existing options.
                hr = pfd->GetOptions(&dwFlags);
                if (SUCCEEDED(hr))
                {
                    // In this case, get shell items only for file system items.
                    hr = pfd->SetOptions(dwFlags | FOS_FORCEFILESYSTEM);
                    if (SUCCEEDED(hr))
                    {
                        // Set the file types to display only. Notice that, this is a 1-based array.
                        hr = pfd->SetFileTypes(ARRAYSIZE(c_rgSaveTypes), c_rgSaveTypes);
                        if (SUCCEEDED(hr))
                        {
                            // Set the selected file type index to Word Docs for this example.
                            hr = pfd->SetFileTypeIndex(INDEX_WORDDOC);
                            if (SUCCEEDED(hr))
                            {
                                // Set the default extension to be ".doc" file.
                                hr = pfd->SetDefaultExtension(L"doc");
                                if (SUCCEEDED(hr))
                                {
                                    // Show the dialog
                                    hr = pfd->Show(NULL);
                                    if (SUCCEEDED(hr))
                                    {
                                        // Obtain the result, once the user clicks the 'Open' button.
                                        // The result is an IShellItem object.
                                        IShellItem* psiResult;
                                        hr = pfd->GetResult(&psiResult);
                                        if (SUCCEEDED(hr))
                                        {
                                            // We are just going to print out the name of the file for sample sake.
                                            PWSTR pszFilePath = NULL;
                                            hr = psiResult->GetDisplayName(SIGDN_FILESYSPATH, &pszFilePath);
                                            if (SUCCEEDED(hr))
                                            {
                                                TaskDialog(NULL,
                                                    NULL,
                                                    L"CommonFileDialogApp",
                                                    pszFilePath,
                                                    NULL,
                                                    TDCBF_OK_BUTTON,
                                                    TD_INFORMATION_ICON,
                                                    NULL);
                                                CoTaskMemFree(pszFilePath);
                                            }
                                            psiResult->Release();
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
                // Unhook the event handler.
                pfd->Unadvise(dwCookie);
            }
            pfde->Release();
        }
        pfd->Release();
    }
    TCHAR filepath[1024];
    if (hr == S_OK)
    {
        std::stringstream pff;
        pff << filepath;
        return pff.str();
    }
    return "";
}

我在从 github 下载的原始文件中更改了他们的代码，它工作得很好。我试图将它复制到另一个项目，但它不起作用（LNK2019 错误）

Answer 1

我想我会为此提供一种 meta-answer：Jerry 怎么知道你需要 link 使用哪些库？ 而且，一如既往，答案就在文档中。

首先，让我们看看那些 linker 错误（为了清楚起见，我将它们删减了一些，使用模板通常会导致冗长/难以阅读的错误消息）：

Unresolved symbol __imp_TaskDialog referenced in function <irrelevant>
Unresolved symbol __imp_PSGetPropertyDescriptionListFromString referenced in function <irrelevant>
Unresolved symbol QISearch referenced in function <irrelevant>

首先，您可以忽略 __imp_ 位。这只是告诉您该函数是从 DLL 导入的。所以这给我们留下了以下未解决的参考：

TaskDialog
PSGetPropertyDescriptionListFromString
QISearch

所以，是时候去谷歌搜索了。

TaskDialog 的文档是 here，如果您向下滚动到页面底部的 'requirements' 部分，您将看到：

Library Comctl32.lib

这就是那个（请注意，这里的大小写无关紧要，我不知道为什么 Microsoft 以如此奇怪的方式记录这些内容）。

同理，我们很容易发现PSGetPropertyDescriptionListFromString is in Propsys.lib, and QISearch在Shlwapi.lib中。故事结束。

我希望向您展示它是如何完成的。每个 Windows 开发人员都需要了解如何执行此操作以及如何查找和阅读 Microsoft 通常提供的（大量）文档。

LNK2019 示例来自 MSDN

LNK2019 with a sample from MSDN

c++

linker-errors

lnk2019

ifiledialog