Android 写入文件到SD卡

1、在ＳＤ卡中创建新文件，通过Environment.getExternalStorageDirectory()来获取ＳＤ卡路径

File file=new File(Environment.getExternalStorageDirectory(),filename);

２、使用SD卡之前先判断SD卡状态

Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)

3、在AndroidManifest.xml中加入读写SD卡权限

 <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
 <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />