add new features to my file manager app

I have a file manager app. I need to add following features to it. 1. Request for sd card access, if not granted already, first time when user wants to perform a write operation on sd card files(delete,rename, move, copy etc) [login to view URL] files from one folder to another in internal storage, sd card and also move files from internal storage to sd card and vice versa 3. sort files and folders according to date, size, name etc Note: the project is being created on API 17 and I want to get it done using methods which does not require me to change API level of the project