解决方法：
flashmx@ubuntu:~$ cvt 1920 1080
# 1920x1080 59.96 Hz (CVT 2.07M9) hsync: 67.16 kHz; pclk: 173.00 MHz
Modeline "1920x1080_60.00" 173.00 1920 2048 2248 2576 1080 1083 1088 1120 -hsync +vsync
flashmx@ubuntu:~$ xrandr --newmode "1920X1080_60.00" 173.00 1920 2048 2248 2576 1080 1083 1088 1120 -hsync +vsync
flashmx@ubuntu:~$ xrandr --addmode Virtual1 "1920X1080_60.00"
flashmx@ubuntu:~$ xrandr --output Virtual1 --mode "1920X1080_60.00"
亲测真实有效。
If the last command doesn't work for you,you can go back to ubuntu display gui setting and can chose the display you have added just now.For me the option was 1904 x 1070 (16:9)
However if you are fine with this experiment and have found the desired screen resolution and to make that permanent,write the all the last 3 commands starting from xrandr --newmode command in your .xprofile file using following command and then save,exit and restart your ubuntu vm and you will get your desired resolution permanently.
（如果上一个命令不为你工作，你可以回到Ubuntu显示界面设置，可以选择你刚才添加的显示。我选择1904×1070（16:9）
但是如果你是好的这个实验和发现所需的屏幕分辨率，使永久的，写的所有的最后3个命令从xrandr --在你的指挥方式。xprofile文件使用下面的命令，然后保存，退出并重新启动你的Ubuntu的虚拟机，你会得到你想要的分辨率永久。）
$ gedit ~/.xprofile