擷取裝置支援的內容類型

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內容類型。 例如，儲存類別可支援資料夾、音訊和影像的內容類型。

如需 WPD 所支援之內容類型的描述，請參閱 WPD_CONTENT_TYPE_ALL 主題。

DeviceCapabilities.cpp 模組中的 ListSupportedContentTypes 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	提供功能類別擷取方法的存取權。
IPortableDevicePropVariantCollection 介面	用來列舉和儲存功能類別資料。

 

在 ListSupportedContentTypes 函式中找到的程式碼幾乎與 ListFunctionalCategories 函式中找到的程式碼完全相同。 (請參閱裝置主題支援的擷 取功能類別 。) 其中一個差異在於 呼叫 IPortableDeviceCapabilities：：GetSupportedContentTypes 方法，此方法會出現在逐一查看功能類別的迴圈內。

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);
    }
}

相關主題

IPortableDevice 介面

IPortableDeviceCapabilities 介面

IPortableDevicePropVariantCollection 介面

程式設計指南