將影像或音樂檔案傳輸至裝置

發行項
06/13/2023

應用程式完成的其中一個最常見作業是將內容傳輸到連線的裝置。

使用下表所述的介面來完成內容傳輸。

介面	描述
IPortableDeviceContent 介面	提供內容特定方法的存取權。
IPortableDeviceDataStream 介面	將內容寫入裝置時使用。
IPortableDeviceValues 介面	用來擷取描述內容的屬性。
IStream 介面	用來簡化內容讀取和寫入裝置。

TransferContentToDevice範例應用程式 ContentTransfer.cpp 模組中的函式示範應用程式如何將內容從電腦傳輸到連線的裝置。在此特定範例中，傳輸的內容可以是包含影像、音樂或連絡人資訊的檔案。

函式完成 TransferContentToDevice 的第一項工作是提示使用者輸入物件識別碼，以識別要傳送的物件。

HRESULT                             hr = S_OK;
WCHAR                               szSelection[81]        = {0};
WCHAR                               szFilePath[MAX_PATH]   = {0};
DWORD                               cbOptimalTransferSize   = 0;
CComPtr<IStream>                    pFileStream;
CComPtr<IPortableDeviceDataStream>  pFinalObjectDataStream;
CComPtr<IPortableDeviceValues>      pFinalObjectProperties;
CComPtr<IPortableDeviceContent>     pContent;
CComPtr<IStream>                    pTempStream;  // Temporary IStream which we use to QI for IPortableDeviceDataStream

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

函式完成 TransferContentToDevice 的第二項工作是呼叫IPortableDevice：：Content方法來建立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);
    }
}

函式完成的 TransferContentToDevice 下一項工作是建立 FileOpen 對話方塊，讓使用者可以指定要傳送之檔案的位置和名稱。

if (SUCCEEDED(hr))
{
    OPENFILENAME OpenFileNameInfo   = {0};

    OpenFileNameInfo.lStructSize    = sizeof(OPENFILENAME);
    OpenFileNameInfo.hwndOwner      = NULL;
    OpenFileNameInfo.lpstrFile      = szFilePath;
    OpenFileNameInfo.nMaxFile       = ARRAYSIZE(szFilePath);
    OpenFileNameInfo.lpstrFilter    = pszFileTypeFilter;
    OpenFileNameInfo.nFilterIndex   = 1;
    OpenFileNameInfo.Flags          = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST;
    OpenFileNameInfo.lpstrDefExt    = pszDefaultFileExtension;

    if (GetOpenFileName(&OpenFileNameInfo) == FALSE)
    {
        printf("The transfer operation was canceled.\n");
        hr = E_ABORT;
    }
}

函 TransferContentToDevice 式會將篩選字串 (wszFileTypeFilter) 傳遞至 GetOpenFileName 方法，以決定使用者可以選擇的檔案類型。 DoMenu如需範例所允許的三個不同篩選範例，請參閱 WpdApiSample.cpp 模組中的函式。

當使用者識別要傳送至裝置的特定檔案之後，函 TransferContentToDevice 式會將該檔案開啟為 IStream 物件，並擷取完成傳輸所需的屬性。

if (SUCCEEDED(hr))
{
    // Open the selected file as an IStream.  This will simplify reading the
    // data and writing to the device.
    hr = SHCreateStreamOnFile(szFilePath, STGM_READ, &pFileStream);
    if (SUCCEEDED(hr))
    {
        // Get the required properties needed to properly describe the data being
        // transferred to the device.
        hr = GetRequiredPropertiesForContentType(guidContentType,           // Content type of the data
                                                 szSelection,              // Parent to transfer the data under
                                                 szFilePath,               // Full file path to the data file
                                                 pFileStream,               // Open IStream that contains the data
                                                 &pFinalObjectProperties);  // Returned properties describing the data
        if (FAILED(hr))
        {
            printf("! Failed to get required properties needed to transfer a file to the device, hr = 0x%lx\n", hr);
        }
    }

    if (FAILED(hr))
    {
        printf("! Failed to open file named (%ws) to transfer to device, hr = 0x%lx\n",szFilePath, hr);
    }
}

呼叫在 IStream 物件上運作的 GetRequiredPropertiesForContentType helper-function 會擷取必要的屬性。 GetRequiredPropertiesForContentTypehelper-function 會建立IPortableDeviceValues物件、擷取下列清單中的屬性，並將其新增至此物件。

父物件識別碼
以位元組為單位的資料流程大小
內容檔案名
沒有副檔名的檔案名 (內容名稱)
內容類型 (影像、音訊或連絡人)
(JFIF、WMA 或 vCard2) 的內容格式

範例應用程式會使用擷取的屬性，在裝置上建立新的內容。這是以三個階段完成：

應用程式會呼叫 IPortableDeviceContent：：CreateObjectWithPropertiesAndData 方法，在裝置上建立新的 IStream 物件。
應用程式會使用此物件從 WPD 驅動程式取得 IPortableDeviceDataStream 物件。
應用程式會使用新的 IPortableDeviceDataStream 物件，透過 StreamCopy 協助程式函式) 將內容寫入裝置 (。協助程式函式會將來源檔案中的資料寫入 IPortableDeviceContent：：CreateObjectWithPropertiesAndData所傳回的資料流程。
應用程式會在目的地資料流程上呼叫 Commit 方法來完成作業。

// 4) Transfer for the content to the device
if (SUCCEEDED(hr))
{
    hr = pContent->CreateObjectWithPropertiesAndData(pFinalObjectProperties,    // Properties describing the object data
                                                     &pTempStream,              // Returned object data stream (to transfer the data to)
                                                     &cbOptimalTransferSize,    // Returned optimal buffer size to use during transfer
                                                     NULL);

    // Once we have the IStream returned from CreateObjectWithPropertiesAndData,
    // QI for IPortableDeviceDataStream so we can use the additional methods
    // to get more information about the object (i.e. The newly created object
    // identifier on the device)
    if (SUCCEEDED(hr))
    {
        hr = pTempStream->QueryInterface(IID_PPV_ARGS(&pFinalObjectDataStream));
        if (FAILED(hr))
        {
            printf("! Failed to QueryInterface for IPortableDeviceDataStream, hr = 0x%lx\n",hr);
        }
    }

    // Since we have IStream-compatible interfaces, call our helper function
    // that copies the contents of a source stream into a destination stream.
    if (SUCCEEDED(hr))
    {
        DWORD cbTotalBytesWritten = 0;

        hr = StreamCopy(pFinalObjectDataStream, // Destination (The Object to transfer to)
                        pFileStream,            // Source (The File data to transfer from)
                        cbOptimalTransferSize,  // The driver specified optimal transfer buffer size
                        &cbTotalBytesWritten);  // The total number of bytes transferred from file to the device
        if (FAILED(hr))
        {
            printf("! Failed to transfer object to device, hr = 0x%lx\n",hr);
        }
    }
    else
    {
        printf("! Failed to get IStream (representing destination object data on the device) from IPortableDeviceContent, hr = 0x%lx\n",hr);
    }

    // After transferring content to the device, the client is responsible for letting the
    // driver know that the transfer is complete by calling the Commit() method
    // on the IPortableDeviceDataStream interface.
    if (SUCCEEDED(hr))
    {
        hr = pFinalObjectDataStream->Commit(0);
        if (FAILED(hr))
        {
            printf("! Failed to commit object to device, hr = 0x%lx\n",hr);
        }
    }

    // Some clients may want to know the object identifier of the newly created
    // object.  This is done by calling GetObjectID() method on the
    // IPortableDeviceDataStream interface.
    if (SUCCEEDED(hr))
    {
        PWSTR pszNewlyCreatedObject = NULL;
        hr = pFinalObjectDataStream->GetObjectID(&pszNewlyCreatedObject);
        if (SUCCEEDED(hr))
        {
            printf("The file '%ws' was transferred to the device.\nThe newly created object's ID is '%ws'\n",szFilePath ,pszNewlyCreatedObject);
        }

        if (FAILED(hr))
        {
            printf("! Failed to get the newly transferred object's identifier from the device, hr = 0x%lx\n",hr);
        }

        // Free the object identifier string returned from the GetObjectID() method.
        CoTaskMemFree(pszNewlyCreatedObject);
        pszNewlyCreatedObject = NULL;
    }
}

IPortableDevice 介面
IPortableDeviceContent 介面
IPortableDeviceDataStream 介面
IPortableDeviceValues 介面
程式設計指南

將影像或音樂檔案傳輸至裝置

意見反應

意見反應

其他資源

將影像或音樂檔案傳輸至裝置

相關主題

意見反應

意見反應

其他資源