UWP，C ++ / Cx FileOpenPicker

Question

有谁知道我做错了什么。

    // STORAGE FILE
    StorageFile^ saveFile;

    // FILE PICKER, FOR SELECTING A SAVE FILE
    FileOpenPicker^ filePicker = ref new FileOpenPicker;

    // ARRAY OF FILE TYPES
    Array<String^>^ fileTypes = ref new Array<String^>(1);
    fileTypes->Data[0] = ".txt";

    filePicker->ViewMode = PickerViewMode::Thumbnail;
    filePicker->SuggestedStartLocation = PickerLocationId::Desktop;
    filePicker->FileTypeFilter->ReplaceAll(fileTypes);

    // THIS SHOULD HOPEFULLY LET US PICK A FILE

    saveFile = filePicker->PickSingleFileAsync();

特别是最后一行：

saveFile = filePicker->PickSingleFileAsync();

我收到以下错误。

  

错误C2440：＆＃39; =＆＃39;：无法转换为＆＃39; Windows :: Foundation :: IAsyncOperation ^＆＃39;到＆＃39; Windows :: Storage :: StorageFile ^＆＃39;

Answer 1

  

错误C2440：＆＃39; =＆＃39;：无法转换为＆＃39; Windows :: Foundation :: IAsyncOperation ^＆＃39;到＆＃39; Windows :: Storage :: StorageFile ^＆＃39;

PickSingleFileAsync是异步方法，返回类型为Windows::Foundation::IAsyncOperation，无法转换为StorageFile类型。正如Hans Passant所说，你可以使用create_task()来等待这种异步操作。

create_task(folderPicker->PickSingleFolderAsync()).then([this](StorageFolder^ folder)
{
    if (folder)
    {
        //do some stuff
    }
    else
    {
        //do some stuff
    }
});

有关详情，请参阅Asynchronous programming in C++。