[Qt-interest] How to add a background image for MainWindow

[Kermit Mei]

Hello, community!

I implemented a MainWindow which inherited from QWidget. Now, I need to
add an background for it. I use 
setStyleSheet("background-image: url(:/images/background.jpg)");
in MainWindow::MainWindow(...), but all the widgets include all the
buttons on it has a background from background.jpg, it looks very
confused. 

How can I correct it?

Thanks:)