获取SD卡的剩余空间

    /**
     * 获取SD卡的剩余空间
     *
     * @return SD卡的剩余的字节数
     */
    public static long getFreeSD()
    {
        long nAvailableCount = 0l;
        StatFs stat = new StatFs(Environment.getExternalStorageDirectory()
                .getAbsolutePath());
        nAvailableCount = (long) (stat.getBlockSize() * ((long) stat
                .getAvailableBlocks() - SDCARD_SYSTEM));
        return nAvailableCount;
    }