Create CSV file with the right permissions

Question

I am building an Android app where I want to export some values to a CSV. I have to problem: either I get an error saying that the permission is denied or I get no errors but no CSV is created.

    FileWriter writer;
    File root = Environment.getExternalStorageDirectory();
    File csvFile = new File(root, "xxx.csv");
    writer = new FileWriter(csvFile);

    String headers = String.format("%s,%s\n", "Timestamp",
            "Value");
    writer.write(headers);
    writer.flush();
    writer.close();

But i get nothing...