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());
}
}
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