我不知道为什么会发生此问题。我只是猜测显卡可能导致此问题，但我不确定。我的电脑（Acer aspire V 13）规格和 ubuntu 版本如下：
----ubuntu version----
Distributor ID: Ubuntu
Description: Ubuntu 18.04.2 LTS
Release: 18.04
Codename: bionic
----computer spec.----
graphics card:
Intel HD Graphics 520
sound:
Intel Sunrise Point-LP HD Audio
storage:
Intel Sunrise Point-LP SATA Controller [AHCI mode]
network:
wlp3s0 Qualcomm Atheros QCA6174 802.11ac Wireless Network Adapter
enp2s0 Realtek RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
network interface:
enp2s0 Ethernet network interface
lo Loopback network interface
wlp3s0 Ethernet network interface
disk:
/dev/sda SAMSUNG MZNLN256
partition:
/dev/sda1 Partition
usb controller:
Intel Sunrise Point-LP USB 3.0 xHCI Controller
bios:
BIOS
bridge:
Intel PCI bridge
Intel Sunrise Point-LP LPC Controller
Intel Sunrise Point-LP PCI Express Root Port #6
Intel Skylake Host Bridge/DRAM Registers
Intel Sunrise Point-LP PCI Express Root Port #5
hub:
Linux Foundation 2.0 root hub
Linux Foundation 3.0 root hub
有没有人遇到同样的问题并解决了？