qwidget - Qt widgets not placed correctly -

i've subclassed qwidget , defined constructor way:

loupingwidget::loupingwidget(qwidget *parent): qwidget(parent) {     qgroupbox *topgroupbox = new qgroupbox(this);      qgraphicsview *xrgbplot = new qgraphicsview(this);     qgraphicsview *yrgbplot = new qgraphicsview(this);     qgraphicsview *loupe = new qgraphicsview(this);     qslider *slider = new qslider(this);      qgridlayout *boxglayout = new qgridlayout;     boxglayout->addwidget(xrgbplot, 0, 0);     boxglayout->addwidget(slider, 0, 1);     boxglayout->addwidget(loupe, 1, 0);     boxglayout->addwidget(yrgbplot, 1, 1);      topgroupbox->setlayout(boxglayout); } 

next, trying add in qdialog:

window::window(qwidget *parent): qdialog(parent) {     loupingwidget *firstloupindwidget = new loupingwidget(this);     loupingwidget *secondloupindwidget = new loupingwidget(this); //  qgraphicsview *mainpicture  = new qgraphicsview(this);      qgridlayout *gridlayout = new qgridlayout; //    gridlayout->addwidget(mainpicture, 0, 0);     gridlayout->addwidget(firstloupindwidget, 1, 0);     gridlayout->addwidget(secondloupindwidget, 1, 1);     setlayout(gridlayout); } 

when 2 lines commented out, 2 widgets placed horizontally. , that's good, when uncomment lines qgraphicsviews, fills entire window.

what doing wrong?

loupingwidget doesn't have layout, when it's added layout, layout can't resize according contents. need create layout (e.g. qgridlayout) in loupingwidget constructor, add topgroupbox layout , set layout loupingwidget's layout.