Android Question Method To create A Filemanager

I Have a Method But I need To use a powerfull method then this one

1- declare a list for folder
2 - declare list for file
3- declare a string to store path
4 - loop throwt all file and check if folder then add to list folder and if file check their type
5- fill list view
6 - ? back button
7-.??....

I resolve it thank's