I found the solution on 18.04 .It's something related with the ui skin。first use keyboard shortcut to active the input method to chinese (or other instead of the default english), click the menu ,select the skin from ubuntu-XXXX to classic or dark。
I found the solution on 18.04 .It's something related with the ui skin。first use keyboard shortcut to active the input method to chinese (or other instead of the default english), click the menu ,select the skin from ubuntu-XXXX to classic or dark。