通过

检索设备的功能对象标识符

  • 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功能对象。 例如，存储类别可能支持三个功能存储对象，每个对象都由唯一标识符字符串标识。 然后，第一个存储对象可由字符串“Storage1”标识，第二个存储对象由字符串“Storage2”标识，第三个对象由字符串“Storage3”标识。

DeviceCapabilities.cpp 模块中的 ListFunctionalObjects 函数演示了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 ListFunctionalObjects 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：：GetFunctionalObjects 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 get the list of
// functional object identifiers associated with a particular
// category.
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 object identifiers for all
                // functional objects within this category
                CComPtr<IPortableDevicePropVariantCollection> pFunctionalObjectIds;
                hr = pCapabilities->GetFunctionalObjects(*pv.puuid, &pFunctionalObjectIds);
                if (SUCCEEDED(hr))
                {
                    printf("Functional Objects: ");
                    DisplayFunctionalObjectIDs(pFunctionalObjectIds);
                    printf("\n\n");
                }
                else
                {
                    printf("! Failed to get functional objects, hr = 0x%lx\n", hr);
                }
            }
            else
            {
                printf("! Invalid functional category found\n");
            }
        }

        PropVariantClear(&pv);
    }
}

IPortableDevice 接口

IPortableDeviceCapabilities 接口

IPortableDevicePropVariantCollection 接口

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