Can't create file using fstream in windows store app 8.1

问题

I'm using direct3D 11.1 to create my game,i want to store player last record in a file so here is my code:(it fails in !File.good() )

fstream File("Score.txt");

            if (!File.good())
            {
                return;
            }
            if (!File.is_open())
            {
                return;
            }
            if (File.bad())
            {
                return;
            }
            Writer.Write("Easy", getString(Scene->Score), File);
            File.close();

and here is my XMLWriter class to write in file:

   class XmlWriter
{
public:
    void Write(string  const &replace, string const &replaceBy, fstream &file)
    {
        fstream tempFile;
        tempFile.open("ScoreT.xml", fstream::out | fstream::trunc | ios::app);
        if (!tempFile)
        {
            return;
        }
        string curLine = "";
        while (!file.eof())
        {
            getline(file, curLine);
            if (findWord(replace, curLine))
            {
                int j = 0;
                while (curLine[j] != replace[0])
                {
                    j++;
                }
                j += replace.size() + 1;
                for (int k = 0; k < replaceBy.size(); k++)
                {
                    curLine[j] = replaceBy[k];
                    j++;
                }
                if (curLine[j] != ',' && curLine[j] != '<')
                {
                    curLine[j] = ' ';
                }
                tempFile << curLine << "\n";
            }
            else
            {
                string temp = "";
                file << temp;
                tempFile << curLine << "\n";
            }
        }
        file.close();
        tempFile.close();
        if (remove("Setting.xml") != 0) perror("Error removing file!");
        rename("ScoreT.xml", "Score.xml");
    }
private:
    bool findWord(string search, string searchLine)
    {
        bool ret = false;
        for (int i = 0, j = 0; i < searchLine.size() && j<search.size(); i++)
        {
            if (search[j] == searchLine[i])
            {
                ret = true;
                j++;
                continue;
            }
            ret = false;
            j = 0;
        }
        return ret;
    }
};

but any time i run it,it can't create a new file and fail! what's the problem with it? Note that i do this in my XAML code.

回答1:

Store apps are only permitted write access to a handful of file paths. By calling fstream::open without a fully qualified path, the API uses the working directory, which in the case of a store app is always the app package path (a path which the app does not have write access to).

The solution is to use a fully qualified path that the app has write access to. For saving player data, your best bet is to use the ApplicationData::Current->RoamingFolder folder, use the Path property to get the full path, and append the filename you want to the string. Then pass the fully qualified file path string to fstream::open and it should succeed.

来源：https://stackoverflow.com/questions/25815285/cant-create-file-using-fstream-in-windows-store-app-8-1