private String getRelativePath(File base, File file) {
		String key = "";
		while (true) {
			if (file.equals(base)) return "";
			if (file.getParentFile() == null) return null;
			if (file.getParentFile().equals(base)) {
				String ret = file.getName()+"/"+key;
				return ret.substring(0,ret.length()-1);
			}
			
			key = file.getName()+"/"+key;
			file = file.getParentFile();			
		}
	}