通过

检索设备支持的内容类型

  • 项目

如 检索设备支持的功能类别 主题中所述，Windows 便携设备可能支持一个或多个功能类别。 任何给定的功能类别都可能支持一个或多个内容类型。 例如，存储类别可能支持文件夹、音频和图像的内容类型。

有关 WPD 支持的内容类型的说明，请参阅 WPD_CONTENT_TYPE_ALL 主题。

DeviceCapabilities.cpp 模块中的 ListSupportedContentTypes 函数演示如何检索所选设备支持的功能类别的内容类型。

应用程序可以使用下表中所述的接口检索设备支持的功能类别。

接口 说明
IPortableDeviceCapabilities 接口 提供对功能类别检索方法的访问。
IPortableDevicePropVariantCollection 接口 用于枚举和存储功能类别数据。

 

在 ListSupportedContentTypes 函数中找到的代码几乎与 ListFunctionalCategories 函数中找到的代码相同。 (请参阅 检索设备支持的功能类别 主题。) 一个区别是调用 IPortableDeviceCapabilities：：GetSupportedContentTypes 方法，该方法显示在循环访问函数类别的循环中。

HRESULT hr = S_OK;
CComPtr<IPortableDeviceCapabilities>            pCapabilities;
CComPtr<IPortableDevicePropVariantCollection>   pCategories;
DWORD dwNumCategories   = 0;

if (pDevice == NULL)
{
    printf("! A NULL IPortableDevice interface pointer was received\n");
    return;
}

// Get an IPortableDeviceCapabilities interface from the IPortableDevice interface to
// access the device capabilities-specific methods.
hr = pDevice->Capabilities(&pCapabilities);
if (FAILED(hr))
{
    printf("! Failed to get IPortableDeviceCapabilities from IPortableDevice, hr = 0x%lx\n",hr);
}

// Get all functional categories supported by the device.
// We will use these categories to enumerate functional objects
// that fall within them.
if (SUCCEEDED(hr))
{
    hr = pCapabilities->GetFunctionalCategories(&pCategories);
    if (FAILED(hr))
    {
        printf("! Failed to get functional categories from the device, hr = 0x%lx\n",hr);
    }
}

// Get the number of functional categories found on the device.
if (SUCCEEDED(hr))
{
    hr = pCategories->GetCount(&dwNumCategories);
    if (FAILED(hr))
    {
        printf("! Failed to get number of functional categories, hr = 0x%lx\n",hr);
    }
}

printf("\n%d Functional Categories Found on the device\n\n", dwNumCategories);

// Loop through each functional category and display its name and supported content types.
if (SUCCEEDED(hr))
{
    for (DWORD dwIndex = 0; dwIndex < dwNumCategories; dwIndex++)
    {
        PROPVARIANT pv = {0};
        PropVariantInit(&pv);
        hr = pCategories->GetAt(dwIndex, &pv);
        if (SUCCEEDED(hr))
        {
            // We have a functional category.  It is assumed that
            // functional categories are returned as VT_CLSID
            // VarTypes.

            if ((pv.puuid != NULL)      &&
                (pv.vt    == VT_CLSID))
            {
                // Display the functional category name
                printf("Functional Category: ");
                DisplayFunctionalCategory(*pv.puuid);
                printf("\n");

                // Display the content types supported for this category
                CComPtr<IPortableDevicePropVariantCollection> pContentTypes;
                hr = pCapabilities->GetSupportedContentTypes(*pv.puuid, &pContentTypes);
                if (SUCCEEDED(hr))
                {
                    printf("Supported Content Types: ");
                    DisplayContentTypes(pContentTypes);
                    printf("\n\n");
                }
                else
                {
                    printf("! Failed to get supported content types from the device, hr = 0x%lx\n",hr);
                }
            }
            else
            {
                printf("! Invalid functional category found\n");
            }
        }

        PropVariantClear(&pv);
    }
}

IPortableDevice 接口

IPortableDeviceCapabilities 接口

IPortableDevicePropVariantCollection 接口

编程指南