You can add session for your kdm session mananger, by typing:"genkdmconf" in your terminal with the authority of root.
But a question is brought up then, if your directory "/etc/X11/xdm" does have a file "xdm-keys" in it, then you can't have a language-choice menue in your kdm greeter.
But are there anyone who can help me? I can't have my fcitx run now.