https://blog.wongcw.com/2018/10/30/android-file-transfer%e8%ae%93mac%e4%b9%9f%e8%83%bd%e8%ae%80%e5%8f%96android%e6%89%8b%e6%a9%9f%e4%b8%ad%e7%9a%84%e8%b3%87%e6%96%99/