Eliminar contenido del dispositivo

Otra operación común realizada por una aplicación WPD es la eliminación de contenido de una ubicación en el dispositivo.

Las operaciones de eliminación de contenido se realizan mediante las interfaces descritas en la tabla siguiente.

Interfaz	Descripción
IPortableDeviceContent (Interfaz)	Proporciona acceso a los métodos de eliminación de contenido.
IPortableDevicePropVariantCollection (Interfaz)	Proporciona acceso a métodos específicos de la propiedad.

 

La función DeleteContentFromDevice del módulo ContentTransfer.cpp de la aplicación de ejemplo muestra cómo una aplicación podría eliminar contenido en el dispositivo. Las operaciones de eliminación de contenido son muy similares a las operaciones de transferencia de contenido. La única diferencia es que durante una eliminación, la aplicación llama a IPortableDeviceContent::D elete en lugar de IPortableDeviceContent::Move. (Consulte el tema Mover contenido en el dispositivo para obtener una descripción de las tareas que conducen a llamar al método Delete).

void DeleteContentFromDevice(
    IPortableDevice* pDevice)
{
    HRESULT                                       hr               = S_OK;
    WCHAR                                         szSelection[81]  = {0};
    CComPtr<IPortableDeviceContent>               pContent;
    CComPtr<IPortableDevicePropVariantCollection> pObjectsToDelete;
    CComPtr<IPortableDevicePropVariantCollection> pObjectsFailedToDelete;

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

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

    // 1) get an IPortableDeviceContent interface from the IPortableDevice interface to
    // access the content-specific methods.
    if (SUCCEEDED(hr))
    {
        hr = pDevice->Content(&pContent);
        if (FAILED(hr))
        {
            printf("! Failed to get IPortableDeviceContent from IPortableDevice, hr = 0x%lx\n",hr);
        }
    }

    // 2) CoCreate an IPortableDevicePropVariantCollection interface to hold the object identifiers
    // to delete.
    //
    // NOTE: This is a collection interface so more than 1 object can be deleted at a time.
    //       This sample only deletes a single object.
    if (SUCCEEDED(hr))
    {
        hr = CoCreateInstance(CLSID_PortableDevicePropVariantCollection,
                              NULL,
                              CLSCTX_INPROC_SERVER,
                              IID_PPV_ARGS(&pObjectsToDelete));
        if (SUCCEEDED(hr))
        {
            if (pObjectsToDelete != NULL)
            {
                PROPVARIANT pv = {0};
                PropVariantInit(&pv);

                // Initialize a PROPVARIANT structure with the object identifier string
                // that the user selected above. Notice we are allocating memory for the
                // PWSTR value.  This memory will be freed when PropVariantClear() is
                // called below.
                pv.vt      = VT_LPWSTR;
                pv.pwszVal = AtlAllocTaskWideString(szSelection);
                if (pv.pwszVal != NULL)
                {
                    // Add the object identifier to the objects-to-delete list
                    // (We are only deleting 1 in this example)
                    hr = pObjectsToDelete->Add(&pv);
                    if (SUCCEEDED(hr))
                    {
                        // Attempt to delete the object from the device
                        hr = pContent->Delete(PORTABLE_DEVICE_DELETE_NO_RECURSION,  // Deleting with no recursion
                                              pObjectsToDelete,                     // Object(s) to delete
                                              NULL);                                // Object(s) that failed to delete (we are only deleting 1, so we can pass NULL here)
                        if (SUCCEEDED(hr))
                        {
                            // An S_OK return lets the caller know that the deletion was successful
                            if (hr == S_OK)
                            {
                                printf("The object '%ws' was deleted from the device.\n", szSelection);
                            }

                            // An S_FALSE return lets the caller know that the deletion failed.
                            // The caller should check the returned IPortableDevicePropVariantCollection
                            // for a list of object identifiers that failed to be deleted.
                            else
                            {
                                printf("The object '%ws' failed to be deleted from the device.\n", szSelection);
                            }
                        }
                        else
                        {
                            printf("! Failed to delete an object from the device, hr = 0x%lx\n",hr);
                        }
                    }
                    else
                    {
                        printf("! Failed to delete an object from the device because we could no add the object identifier string to the IPortableDevicePropVariantCollection, hr = 0x%lx\n",hr);
                    }
                }
                else
                {
                    hr = E_OUTOFMEMORY;
                    printf("! Failed to delete an object from the device because we could no allocate memory for the object identifier string, hr = 0x%lx\n",hr);
                }

                // Free any allocated values in the PROPVARIANT before exiting
                PropVariantClear(&pv);
            }
            else
            {
                printf("! Failed to delete an object from the device because we were returned a NULL IPortableDevicePropVariantCollection interface pointer, hr = 0x%lx\n",hr);
            }
        }
        else
        {
            printf("! Failed to CoCreateInstance CLSID_PortableDevicePropVariantCollection, hr = 0x%lx\n",hr);
        }
    }
}

Temas relacionados

IPortableDevice (Interfaz)

IPortableDeviceContent (Interfaz)

IPortableDevicePropVariantCollection (Interfaz)

Guía de programación