UE4C++调用windows系统文件夹路径选取窗口

虚幻中是可以创建不同系统的桌面实例的，并且提供不同的函数接口进行不同操作

OpendDirectoryDialog函数进行文件夹路径的选择

第一步：创建一个桌面实例，根据参数类型给参数

参数解读：ParentWindowHandle 父类窗口类型

     DialogTitle   对话框的标题

     DefaultPath 打开对话框的默认路径

     OutFolderName 用户自定义选择的文件路径名字

创建一个 返回FString类型的函数

通过FPaths:ConvertRelativePathToFull(FPaths::ProjectDir)获得项目的路径

OpenFileDialog根据类型选择文件资源

/** 
 * Opens the "open file" dialog for the platform
 *
 * @param ParentWindowHandle      The native handle to the parent window for this dialog
 * @param DialogTitle           The text for the title of the dialog window
 * @param DefaultPath           The path where the file dialog will open initially
 * @param DefaultFile           The file that the dialog will select initially
 * @param Flags                   Details about the dialog. See EFileDialogFlags.
 * @param FileTypes                The type filters to show in the dialog. This string should be a "|" delimited list of (Description|Extensionlist) pairs. Extensionlists are ";" delimited.
 * @param OutFilenames          The filenames that were selected in the dialog
 * @param OutFilterIndex         The type that was selected in the dialog
 * @return true if files were successfully selected
 */
virtual bool OpenFileDialog(const void* ParentWindowHandle, const FString& DialogTitle, const FString& DefaultPath, const FString& DefaultFile, const FString& FileTypes, uint32 Flags, TArray<FString>& OutFilenames, int32& outFilterIndex ) = 0;