Centralize a Frame in Another Frame in QT Designer - qt

Question

In the first picture I designed a prototype. The MainWindow includes widget and three frames. The center frame has another frame, and when I run in the application in full screen there is a size problem in the center frame, as you can see in the second picture. I want to center the frame in its frame. How can I do that?

Answer 1

You can do it easily from Qt Designer. Just add another Horizontal Layout into the middle Frame. Then add your Widget into the layout, go to the Object Manager, call context menu on your widget, click Layout Alignment and choose Center horizontally.
Here is the .ui file which I have just created to check your problem:
<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>MainWindow</class>
<widget class="QMainWindow" name="MainWindow">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>965</width>
<height>502</height>
</rect>
</property>
<property name="windowTitle">
<string>MainWindow</string>
</property>
<widget class="QWidget" name="centralWidget">
<layout class="QHBoxLayout" name="horizontalLayout">
<item>
<layout class="QHBoxLayout" name="horizontalLayout_3">
<item>
<widget class="QFrame" name="frame_2">
<property name="frameShape">
<enum>QFrame::StyledPanel</enum>
</property>
<property name="frameShadow">
<enum>QFrame::Raised</enum>
</property>
</widget>
</item>
<item>
<widget class="QFrame" name="frame_3">
<property name="frameShape">
<enum>QFrame::StyledPanel</enum>
</property>
<property name="frameShadow">
<enum>QFrame::Raised</enum>
</property>
<widget class="QWidget" name="horizontalLayoutWidget_2">
<property name="geometry">
<rect>
<x>9</x>
<y>9</y>
<width>291</width>
<height>411</height>
</rect>
</property>
<layout class="QHBoxLayout" name="horizontalLayout_2">
<item alignment="Qt::AlignHCenter|Qt::AlignVCenter">
<widget class="QListWidget" name="listWidget"/>
</item>
</layout>
</widget>
</widget>
</item>
<item>
<widget class="QFrame" name="frame">
<property name="frameShape">
<enum>QFrame::StyledPanel</enum>
</property>
<property name="frameShadow">
<enum>QFrame::Raised</enum>
</property>
</widget>
</item>
</layout>
</item>
</layout>
</widget>
<widget class="QMenuBar" name="menuBar">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>965</width>
<height>23</height>
</rect>
</property>
</widget>
<widget class="QToolBar" name="mainToolBar">
<attribute name="toolBarArea">
<enum>TopToolBarArea</enum>
</attribute>
<attribute name="toolBarBreak">
<bool>false</bool>
</attribute>
</widget>
<widget class="QStatusBar" name="statusBar"/>
</widget>
<layoutdefault spacing="6" margin="11"/>
<resources/>
<connections/>
</ui>
Edition 1: Basically with above example I managed to reproduce your bug. I have added horizontal layout inside middle frame but while changing the size middle widget has aligned to the left side.
The answer on your question is here: Make QHorizontalLayout expand inside QFrame
You have to add Horizontal Layout into your middle Frame. Then you have to call context menu of the Middle Frame, click Layout -> Layout Horizontally. Add your widget in the layout. Most probably you widget will expand its width to the width of the Main Window. Change SizePolicy to fixed. At this point your problem should be solved.

Answer 2

you can create programatically like this:
overwrite this functions: QSize sizeHint() and QSize minimumSizeHint()
here an example:
.h
#ifndef LATERALBOARD_H
#define LATERALBOARD_H
#include <QBasicTimer>
#include <QFrame>
#include <QPointer>
QT_BEGIN_NAMESPACE
class QLabel;
QT_END_NAMESPACE
class LateralBoard : public QFrame
{
Q_OBJECT
public:
LateralBoard(QWidget *parent = nullptr);
QSize sizeHint() const override;
QSize minimumSizeHint() const override;
private:
enum { BoardWidth = 10, BoardHeight = 12 };
};
#endif
.cpp
#include <QKeyEvent>
#include <QLabel>
#include <QPainter>
LateralBoard::LateralBoard(QWidget *parent)
: QFrame(parent)
{
setFrameStyle(QFrame::Panel | QFrame::Sunken);
setFocusPolicy(Qt::StrongFocus);
}
QSize LateralBoard::sizeHint() const
{
return QSize(100, 100);
}
QSize LateralBoard::minimumSizeHint() const
{
return QSize(BoardWidth * 5 + frameWidth() * 2,
BoardHeight * 5 + frameWidth() * 2);
}
and in your main window you should use a layout to set the position
QGridLayout *layout = new QGridLayout;
LateralBoard *lateralBoard = new LateralBoard;
layout->addWidget(lateralBoard, 2, 6);
setLayout(layout);