ibus not working in Kubuntu 18.04 KDE Plasma

I have installed Kubuntu 18.04 (installed by kubuntu-18.04-desktop-amd64.iso), and I want to input Chinese. So I installed IBus, but it is not working. I used the following steps to install IBus:

1. sudo apt-install ibus ibus-qt4 ibus-gkt ibus-libpinyin ibs-m17n
2. run ibus-daemon -drx
3. run ibus-setup, and choose Chinese pinyin input method
4. open a Kate, choose input method, and it not working

Then, I configured IBUS following this wiki: https://wiki.archlinux.org/index.php/IBus#Chinese

firstly,

export GTK_IM_MODULE=ibus
export XMODIFIERS=@im=ibus
export QT_IM_MODULE=ibus

secondly,

install qt4-qtconfig

then run

qtconfig-qt4

and Interface > Default Input Method, select ibus instead of xim.

thirdly,

export QT_IM_MODULE=ibus to ~/.xprofile (make a file)

then, reboot OS，but it is still not working, what's wrong with my operation?