一个非常简单的音乐播放器项目源码，可以把SD卡上的音乐扫描出来并填充到ListView里，然后还有暂停、结束、播放、上一曲、下一曲、退出、后台等基本功能，支持后台播放(A very simple source code for a music player project, which can scan the music on the SD card and fill it into the ListView, and then there are basic functions such a