Set widget as central widget in a QMainWindow

[gtnoob]

Most the objects in the example code does not have default parent objects

What exactly does this mean?
Are you refering to w1 and w2?

[Santosh Reddy]

Yes, they should look like

widget1 = new w1(this);
    widget2 = new w2(this);

widget1 = new w1(this);
    widget2 = new w2(this);

To copy to clipboard, switch view to plain text mode 

[gtnoob]

Does this ( http://qt-project.org/doc/qt-5.0/qtc...jecttrees.html ) explain the "because..." of your point of view?

[Santosh Reddy]

Yes, I mean the same