一、将源更换为国内的源，这样下载和更新软件的速度会快很多。将/etc/apt/sources.list文件的内容更换为如下：
#默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释 deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted universe multiverse #deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse #deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse #deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted universe multiverse #deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted universe multiverse #预发布软件源，不建议启用 #deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse #deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse
二、更新软件源，运行下面的两个命令:
sudo apt update sudo apt upgrade
三、安装搜狗输入法：
1、首先要安装fcitx:
sudo apt install fcitx
2、然后去搜狗输入法的官网下载Ubuntu版本的的搜狗输入法:http://pinyin.sogou.com/linux/
安装输入法，运行下面的命令。最后在语言设置处使用fcitx并添加搜狗输入法，注销后再进入系统就可以使用搜狗输入法了。
sudo dpkg -i sogoupinyin_2.1.0.0086_amd64.deb