將內容從裝置傳輸到電腦

WPD 應用程式完成的一個常見作業是將內容從連線的裝置傳輸到電腦。

使用下表所述的介面來完成內容傳輸。

介面	描述
IPortableDeviceContent 介面	提供 IPortableDeviceProperties 介面的存取權。
IPortableDeviceProperties 介面	提供屬性特定方法的存取權。
IPortableDeviceResources 介面	用來儲存指定設定檔的屬性索引鍵。
IStream 介面	用來讀取和寫入資料。

 

TransferContentFromDevice範例應用程式 ContentTransfer.cpp 模組中的 函式示範應用程式如何將連絡資訊從連線的裝置傳輸到電腦。

函式完成 TransferContentFromDevice 的第一項工作是提示使用者在裝置上輸入父物件的物件識別碼， (該裝置上將傳送內容) 。

HRESULT                            hr                   = S_OK;
WCHAR                              szSelection[81]      = {0};
CComPtr<IPortableDeviceContent>    pContent;
CComPtr<IPortableDeviceResources>  pResources;
CComPtr<IPortableDeviceProperties> pProperties;
CComPtr<IStream>                   pObjectDataStream;
CComPtr<IStream>                   pFinalFileStream;
DWORD                              cbOptimalTransferSize = 0;
CAtlStringW                        strOriginalFileName;

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


// Prompt user to enter an object identifier on the device to transfer.
printf("Enter the identifer of the object you wish to transfer.\n>");
hr = StringCbGetsW(szSelection,sizeof(szSelection));
if (FAILED(hr))
{
    printf("An invalid object identifier was specified, aborting content transfer\n");
}

下一個步驟是擷取範例用來存取內容特定方法的 IPortableDeviceContent 物件。

if (SUCCEEDED(hr))
{
    hr = pDevice->Content(&pContent);
    if (FAILED(hr))
    {
        printf("! Failed to get IPortableDeviceContent from IPortableDevice, hr = 0x%lx\n",hr);
    }
}

下一個步驟是擷取範例用來存取資源特定方法的 IPortableDeviceResources 物件。

if (SUCCEEDED(hr))
{
    hr = pContent->Transfer(&pResources);
    if (FAILED(hr))
    {
        printf("! Failed to get IPortableDeviceResources from IPortableDeviceContent, hr = 0x%lx\n",hr);
    }
}

下一個步驟是擷取範例用來讀取從裝置傳輸的資料的 IStream 物件。

if (SUCCEEDED(hr))
{
    hr = pResources->GetStream(szSelection,             // Identifier of the object we want to transfer
                               WPD_RESOURCE_DEFAULT,    // We are transferring the default resource (which is the entire object's data)
                               STGM_READ,               // Opening a stream in READ mode, because we are reading data from the device.
                               &cbOptimalTransferSize,  // Driver supplied optimal transfer size
                               &pObjectDataStream);
    if (FAILED(hr))
    {
        printf("! Failed to get IStream (representing object data on the device) from IPortableDeviceResources, hr = 0x%lx\n",hr);
    }
}

下一個步驟是在裝置上擷取物件的檔案名。 此字串用來在電腦上建立對應的檔案名。 如果物件在裝置上沒有檔案名，物件的識別碼會轉換成字串，並用來建立目的地檔案名。

if (SUCCEEDED(hr))
{
    hr = pContent->Properties(&pProperties);
    if (SUCCEEDED(hr))
    {
        hr = GetStringValue(pProperties,
                            szSelection,
                            WPD_OBJECT_ORIGINAL_FILE_NAME,
                            strOriginalFileName);
        if (FAILED(hr))
        {
            printf("! Failed to read WPD_OBJECT_ORIGINAL_FILE_NAME on object '%ws', hr = 0x%lx\n", szSelection, hr);
            strOriginalFileName.Format(L"%ws.data", szSelection);
            printf("* Creating a filename '%ws' as a default.\n", (PWSTR)strOriginalFileName.GetString());
            // Set the HRESULT to S_OK, so we can continue with our newly generated
            // temporary file name.
            hr = S_OK;
        }
    }
    else
    {
        printf("! Failed to get IPortableDeviceProperties from IPortableDeviceContent, hr = 0x%lx\n", hr);
    }
}

在此之後，此範例會建立目的地 IStream 物件。

if (SUCCEEDED(hr))
{
    hr = SHCreateStreamOnFile(strOriginalFileName, STGM_CREATE|STGM_WRITE, &pFinalFileStream);
    if (FAILED(hr))
    {
        printf("! Failed to create a temporary file named (%ws) to transfer object (%ws), hr = 0x%lx\n",(PWSTR)strOriginalFileName.GetString(), szSelection, hr);
    }
}

最後，來源 IStream 物件會複製到電腦上的目的地。

if (SUCCEEDED(hr))
{
    DWORD cbTotalBytesWritten = 0;

    // Since we have IStream-compatible interfaces, call our helper function
    // that copies the contents of a source stream into a destination stream.
    hr = StreamCopy(pFinalFileStream,       // Destination (The Final File to transfer to)
                    pObjectDataStream,      // Source (The Object's data to transfer from)
                    cbOptimalTransferSize,  // The driver specified optimal transfer buffer size
                    &cbTotalBytesWritten);  // The total number of bytes transferred from device to the finished file
    if (FAILED(hr))
    {
        printf("! Failed to transfer object from device, hr = 0x%lx\n",hr);
    }
    else
    {
        printf("* Transferred object '%ws' to '%ws'.\n", szSelection, (PWSTR)strOriginalFileName.GetString());
    }
}

相關主題

IPortableDevice 介面

IPortableDeviceContent 介面

IPortableDeviceValues 介面

程式設計指南