从sd卡上的某个文件夹下的txt文件进行写入文件和读取文件的操作-On the sd card from a folder of TXT file for written to the file and reading files operation

Android文件管理:列出手机SD卡中文件系统，支持文件属性查看及对文件的操作-Android File Management:show the file system on cellphone s SD-card, support opeation on files and is able to show properties of files