Cannot get a QT "hello world" to work! - qt

Question

#include <QtCore/QCoreApplication>
#include <QtGui/QLabel>
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QLabel label("Hello world");
label.show();
return a.exec();
}
I am using QTCreator, I installed QT 4.7 on windows.
Now every time I compile I get this error:
:: error: collect2: ld returned 1 exit status
With mingw32 giving me the following
tmp/obj/debug_shared/main.o: In function `main':
E:\Qt\2010.04\qt\QTHello-build-desktop/../QTHello/main.cpp:6: undefined reference to `_imp___ZN6QLabelC1ERK7QStringP7QWidget6QFlagsIN2Qt10WindowTypeEE'
E:\Qt\2010.04\qt\QTHello-build-desktop/../QTHello/main.cpp:8: undefined reference to `_imp___ZN6QLabelD1Ev'
E:\Qt\2010.04\qt\QTHello-build-desktop/../QTHello/main.cpp:8: undefined reference to `_imp___ZN6QLabelD1Ev'
collect2: ld returned 1 exit status
mingw32-make[1]: *** [debug\QTHello.exe] Error 1
mingw32-make: *** [debug-all] Error 2
The process "E:/Qt/2010.04/mingw/bin/mingw32-make.exe" exited with code %2.
Error while building project QTHello (target: Desktop)
When executing build step 'Make'
Whats the problem??

Answer 1

Create a Qt GUI project and olny then write what you have written.

Answer 2

Your project file is probably not including the required stuff. Do you have either
TEMPLATE = app
or
QT += gui
in your .pro file?

Answer 3

Are you linking with QtGui? If you don't, do it.

Answer 4

Also, for UI applications you must use QApplication. QCoreApplication is for CLI-only tools.

Answer 5

You want to create a Hello World app with QT? Really simple:
Create a new GUI app into QtCreator
Open the ui file and add a label using the QtDesigner embedded into QtCreator
Compile and launch
You have your Hello World application done with Qt
Then if you want to know how to write a QTGui application, just open files in project to see what is written in them.