代码取自小米的文件管理器

public static class SDCardInfo {      public long total;        public long free;  }    public static SDCardInfo getSDCardInfo() {      String sDcString = android.os.Environment.getExternalStorageState();        if (sDcString.equals(android.os.Environment.MEDIA_MOUNTED)) {          File pathFile = android.os.Environment.getExternalStorageDirectory();            try {              android.os.StatFs statfs = new android.os.StatFs(pathFile.getPath());                // 获取SDCard上BLOCK总数              long nTotalBlocks = statfs.getBlockCount();                // 获取SDCard上每个block的SIZE              long nBlocSize = statfs.getBlockSize();                // 获取可供程序使用的Block的数量              long nAvailaBlock = statfs.getAvailableBlocks();                // 获取剩下的所有Block的数量(包括预留的一般程序无法使用的块)              long nFreeBlock = statfs.getFreeBlocks();                SDCardInfo info = new SDCardInfo();              // 计算SDCard 总容量大小MB              info.total = nTotalBlocks * nBlocSize;                // 计算 SDCard 剩余大小MB              info.free = nAvailaBlock * nBlocSize;                return info;          } catch (IllegalArgumentException e) {              Log.e(LOG_TAG, e.toString());          }      }        return null;  }