Can't use ibus Input Method for type Chinese character

Hi, there!
I need help because I can't input any Chinese character for Qt5 based application, include QtCreator when build with Qt5.1.

I just know I need build D-Bus for plugins/platforminputcontexts/ibus.
Then I did, and I can sure QtCreator loaded the ibus plugins.
Here is the full log: http://pastebin.mozilla.org/2393461

But I still can't input Chinese in QtCreator, because ibus tell me there `No input window`.

I asked in #qt, #qt-labs, and #qt-cn, but seems nobody know why and how.
So I think it's maybe is a bug.
Any comments are welcome.
Help needed. thanks a lot!

loaden@qpsoft:~$ locale
LANG=en_US.UTF-8
LANGUAGE=en_US:en
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=