1. 修改source list，
   首先备份源列表

sudo cp /etc/apt/sources.list /etc/apt/sources.list_backup

打开sources.list文件修改

sudo vim /etc/apt/sources.list

用下面阿里原替换掉文件中所有的内容，保存编辑好的文件

deb http://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiverse 
deb http://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiverse 
deb http://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiverse 
deb http://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiverse 
deb http://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiverse 
deb-src http://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiverse 
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiverse 
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiverse 
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiverse 
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiverse

刷新列表，注意一定要执行刷新

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install build-essential

2. 发现sudo apt-get install ros-melodic-rviz 还是404，那么更改软件源版本号，参考这篇文章

sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu bionic main" > /etc/apt/sources.list.d/ros-latest.list'
sudo apt-key adv --keyserver 'hkp://keyserver.ubuntu.com:80' --recv-key C1CF6E31E6BADE8868B172B4F42ED6FBAB17C654
sudo apt-get update

再次sudo apt-get install ros-melodic-rviz就ok了

3. rviz无法显示的问题
   首先删除保存好的rviz，运行最初始化的配置
   rviz运行后会选择保存在/home/cbc/.rviz/default.rviz
   删除之后，重新运行

roscore
rosrun rviz rviz