/**
     * 计算SD卡可用空间
     *
     * @return 单位KB
     */
    public static long getAvailableSize() {

        String path = Environment.getExternalStorageDirectory().getPath();// 获取SD卡得根路径
        StatFs stat = new StatFs(path);
        long availableBlocks = stat.getAvailableBlocks();// 获取空闲BLOCK数量
        long blockSize = stat.getBlockSize();// 获取BLOCK的大小
        long availableSize = availableBlocks * blockSize;
        // availableSize/1024 单位KB
        // availableSize/1024 /1024 单位MB
        return availableSize / 1024;
    }

    /**
     * 计算SD总空间大小
     *
     * @return 单位KB
     */
    public static long getAllSize() {

        String path = Environment.getExternalStorageDirectory().getPath();
        StatFs stat = new StatFs(path);
        long blockSize = stat.getBlockSize();
        long availableBlocks = stat.getBlockCount();
        return availableBlocks * blockSize / 1024;
    }



    /** 取SD卡路径 **/
    public static String getSDPath() {
        File sdDir = null;
        boolean sdCardExist = Environment.getExternalStorageState().equals(
                android.os.Environment.MEDIA_MOUNTED);  //判断sd卡是否存在
        if (sdCardExist) {
            sdDir = Environment.getExternalStorageDirectory();  //获取根目录
        }
        if (sdDir != null) {
            return sdDir.toString();
        } else {
            return "";
        }
    }