How to Clear all the Widgets in Parent Widgets?

To take care of the recursivity problem pointed out by @galinette you can just remove the widgets in a while loop

while ( QWidget* w = findChild<QWidget*>() )
    delete w;

Previous answer is wrong!! You cannot use findChildren to delete a widget's children, because Qt4's findChildren recursively lists children. Therefore, you will delete children of children, which then may be deleted twice, potentially crashing your app.

More generally, in Qt, taking a list of QObject pointers and deleting them one by one is dangerous, as destroying an object may chain-destroy other objects, due to the parent ownership mechanism, or by connecting a destroyed() signal to a deleteLater() slot. Therefore, destroying the first objects in the list may invalidate the next ones.

You need to list children widgets either by:

• Passing the Qt::FindDirectChildrenOnly flag to findChild if you are using Qt5 (which did not exist when the question was asked...)
• Using QLayout functions for listing items,
• Using QObject::children, and for each test if it is a widget using isWidgetType() or a cast
• Using findChild() in a loop and delete the result until it returns a null pointer