Windows::Storage::ApplicationData::Current 在 C++ 中找不到 [英] Windows::Storage::ApplicationData::Current Not Found in C++

问题描述

我的 C++ 代码，它是 媒体基础转换的一部分 倾向于能够在 Windows Store App (Metro) 中运行

My C++ code, which is part of Media Foundation Transform tend to able to run in Windows Store App (Metro)

我修改了 C++ GrayscaleTransform 以包含以下代码.

I modify the C++ GrayscaleTransform to include the following code.

但是，我的 C++ 代码无法定位命名空间 Windows::Storage.

However, my C++ code fails to locate namespace Windows::Storage.

LPCWSTR zPath = Windows::Storage::ApplicationData::Current->TemporaryFolder->Path->Data();

我需要做任何其他设置吗?

Is there any additional settings I need to do?

我可以通过打开使用 Windows 运行时扩展来编译它.

I can make it compiled, by turning on Consume Windows Runtime Extension.

但是这样做，它会给我额外的链接错误和警告.

But by doing this, it will give me additional linking error and warnings.

warning LNK4197: export 'DllGetActivationFactory' specified multiple times; using first specification 
warning LNK4197: export 'DllCanUnloadNow' specified multiple times; using first specification
warning LNK4197: export 'DllGetActivationFactory' specified multiple times; using first specification 
warning LNK4197: export 'DllCanUnloadNow' specified multiple times; using first specification
error LNK2005: _DllCanUnloadNow@0 already defined in dllmain.obj 
error LNK1169: one or more multiply defined symbols found

注释掉 DllCanUnloadNow 会产生运行时错误.

Comment out DllCanUnloadNow will produce runtime error.

我在

// GrayscaleTransform.dll!Microsoft::WRL::Details::ModuleBase::ModuleBase()  Line 155 + 0x46 bytes  C++

    ModuleBase() throw()
    {
#ifdef _DEBUG
        // This indicates that there were two instances of the module created or race conditon during module creation
        // If you are creating object with new/delete please make sure that you haven't created more than one module 
        // and you disabled static initalization with __WRL_DISABLE_STATIC_INITIALIZE__
        // otherwise please initialize/create module in main()
        __WRL_ASSERT__(::InterlockedCompareExchangePointer(reinterpret_cast<void* volatile*>(&module_), this, nullptr) == nullptr &&
            "The module was already instantiated");

        SRWLOCK initSRWLOCK = SRWLOCK_INIT;
        __WRL_ASSERT__(reinterpret_cast<SRWLOCK*>(&moduleLock_)->Ptr == initSRWLOCK.Ptr && "Different value for moduleLock_ than SRWLOCK_INIT");
        (initSRWLOCK);
#else
        module_ = this;
#endif
    }

推荐答案

出现链接器错误是因为您在 GrayscaleTransform 项目中启用了 C++/CX.您的项目定义了 dllmain.cpp 中列出的入口点.当您启用 C++/CX 时，vccorlib 会链接到您的模块中，并且它还定义了这些入口点.

The linker errors occur because you enabled C++/CX in the GrayscaleTransform project. Your project defines the listed entry points in dllmain.cpp. When you enable C++/CX, vccorlib gets linked into your module, and it also defines these entry points.

发生运行时错误是因为 vccorlib 中的 C++/CX 基础结构创建了一个模块，而您的入口点尝试创建不同类型的模块.一个模块中只能有一个模块.

The runtime error occurs because the C++/CX infrastructure in vccorlib creates a Module, and your entry point tries to create a different kind of Module. There can only be one Module in a module.

您需要对 GrayscaleTransform 项目进行更多更改才能在其中使用 C++/CX:

You need to make a few more changes to the GrayscaleTransform project to be able to use C++/CX in it:

• 从 dllmain.cpp 中删除四个 Dll*() 函数.您将依赖 vccorlib 中链接的定义.请注意，仍然需要类注册(ActivatableClass(CGrayscale)).

在 C++ 预处理器选项中，确保 _WINRT_DLL 在预处理器定义"中定义.

In the C++ Preprocessor options, ensure that _WINRT_DLL is defined in the "Preprocessor Definitions."

在链接器输入选项中，删除模块定义文件".

In the Linker input options, remove the "Module Definition File."

请注意，使用 WRL 混合 C++/CX 和低级"C++ 时需要非常小心.大多数涉及 C++/CX 类型的表达式都会抛出异常，您必须确保不允许任何异常跨越 ABI 边界.

Note that you will need to be very careful when mixing C++/CX and "low-level" C++ using WRL. Most expressions that involve C++/CX types can throw exceptions, and you must ensure that no exceptions are ever allowed to cross the ABI boundary.

或者，考虑不使用 C++/CX，而是在整个项目中使用 WRL.它会更冗长，但如果您已经在项目的其他部分使用 WRL，它可能更有意义.

Alternatively, consider not using C++/CX and instead using WRL throughout your project. It will be more verbose, but if you are already using WRL for other parts of the project, it may make more sense.

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