I don't think it is possible to get the file path before deleting it.Consider the logic behind,you want to delete a file,so FileObserver don't let you notify until you delete it and also you don't get that path before deleting.
But i think it could be done implementing some simple things.I don't familiar with FileObserver,so i don't talk about that.I assume,you have the list of files that you want to delete or it may be a list works like File Manager.
So when you click on specific file item of that listview you can get the path of that file from code behind by:
File file = new File("fileName.txt");
String filePath = file.getAbsolutePath();
You can then prompt a confirmation dialog asking user he want to delete that file or not?If user choose delete then you can do it by:
File file = new File(selectedFilePath);
boolean deleted = file.delete();
But look, before deleting you have the file path of it, isn't it?