擷取裝置的功能對象標識碼

如 擷取裝置 支援的功能類別主題所述，Windows 可攜式裝置可能支援一或多個功能類別。 任何指定的功能類別都可能支援一或多個功能物件。 例如，記憶體類別可能支援三個功能儲存物件，每個物件都由唯一標識符字串識別。 然後，第一個記憶體物件可由字串 「Storage1」 識別，第二個則由字串 「Storage2」 識別，第三個則由字元串 「Storage3」 來識別。

DeviceCapabilities.cpp模組中的 ListFunctionalObjects 函式示範如何擷取所選裝置所支援之功能類別的內容類型。

您的應用程式可以使用下表所述的介面，擷取裝置所支援的功能類別。

介面	描述
IPortableDeviceCapabilities 介面	提供取得功能類別檢索方法的權限。
IPortableDevicePropVariantCollection 介面	用來列舉及儲存功能類別數據。

 

ListFunctionalObjects 函式中找到的程式代碼與 ListFunctionalCategories 函式中找到的程式代碼幾乎完全相同。 （請參閱 擷取裝置支援的功能類別 主題）。唯一的差異是呼叫 IPortableDeviceCapabilities::GetFunctionalObjects 方法，此方法會出現在遍歷功能類別的循環中。

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);
    }
}

相關主題

IPortableDevice 介面

IPortableDeviceCapabilities 介面

IPortableDevicePropVariantCollection 介面

程式設計手冊