UWP，C++/Cx FileOpenPicker

Question

有沒有人知道我在做什麼錯了。

// 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(); 

特別是最後一行：

saveFile = filePicker->PickSingleFileAsync(); 

我碰到下面的錯誤。

錯誤C2440： '='：「=：無法從 '視窗：基金會:: IAsyncOperation ^' 到 '視窗::存儲:: StorageFile ^'

Answer 1

錯誤C2440轉換視窗：基金會:: IAsyncOperation ^：」不能從轉換'到‘視窗::存儲:: StorageFile ^’

PickSingleFileAsync是異步方法，並返回類型爲Windows::Foundation::IAsyncOperation，它不能被轉換到StorageFile類型。 Hans Passant說，你可以使用create_task()來等待這個異步操作。

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

欲瞭解更多請參閱Asynchronous programming in C++。