How to run QT application on X-window of the embedded platform

Hi, I have an urgent problem with QT run the embedded platform：
I have an embedded EVM-Board, which runs Ubuntu with X-window desktop. The system runs like a PC linking monitor, keyboard and mouse.

Now I want to run a QT application on X-window of the embedded system. After I downloaded QT-lib and QT-application to the file-system and run the QT-application on the terminal, the application could run and the printf-info had no problem. However, there was no QT-window to display on the monitor.

I guess there is someting wrong with my compliled QT-lib or lack of some QT-tools。

Please tell me where is my problem, and whether X-window system needs QVFB to run QT application (no matter on X86 or embedded platform)？

My enviorment:
hardware platform: TI DM8148
complile system: Ubuntu 11.04
complie tool：linux-arm-gnueabi-g++
embedded system : Ubuntu 11.04
QT opensource：qt-everywhere-opensource-src-4.8.1.tar.gz

my install QT-lib configure:
./configure -prefix /usr/local/Trolltech/Qt-4.8.1 -arm -xplatform qws/linux-arm-gnueabi-g++ -embedded arm -little-endian -release -opensource -fast -no-accessibility -scripttools -svg -webkit -shared -javascript-jit -qt-sql-sqlite -no-qt3support -no-mmx -no-3dnow -no-sse -no-sse2 -silent -qt-libpng -qt-libjpeg -qt-libtiff -make libs -nomake examples -nomake docs -nomake demo -no-nis -no-cups -no-iconv -no-dbus -qt-freetype -armfpa -qt-gfx-linuxfb -qt-gfx-transformed -qt-gfx-multiscreen -no-gfx-vnc -no-gfx-qvfb -qt-kbd-linuxinput -qt-mouse-linuxinput -no-glib

board export:
export QTDIR=/home/qt
export LD_LIBRARY_PATH=/lib/qt-lib
export QT_QWS_FONTDIR=/lib/qt-lib/fonts
export QWS_DISPLAY=“LinuxFb:/dev/fb0”