Archived:How to use QWidget

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Qt Quick should be used for all UI development on mobile devices. The approach described in this article (based on QWidget) is deprecated.

Article Metadata

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Tested with

Devices(s): Symbian emulator

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Compatibility

Platform(s): Qt

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Article

Keywords: QWidget

Created: kamaljaiswal (17 Jan 2009)

Last edited: hamishwillee (11 Oct 2012)

Introduction

The QWidget class is the base class of all user interface objects.It receives mouse, keyboard and other events from the window system, and paints a representation of itself on the screen.Every widget is rectangular, and are sorted in a Z-order.

A Widget is called a window if it is not embedded in a parent widget. Non window widgets are used as a child widgets. Most of the Widgets in Qt are used as a child widgets.

When a widgets is used as a container to group a number of child widgets, it is known as a composite widget.

Various Function

• The size of a QWidget can be set or modified with the method QWidget::resize().

QWidget window;
window.resize(100,50);

• Qt provide a system of layout to organize the size and position of children widgets. Here is an example using QVBoxLayout to align two buttons vertically:

QVBoxLayout *layout=new QVBoxLayout();
layout->addWidget(new QPushButton("Hello"));
layout->addWidget(new QPushButton("Bye Bye"));
window.setLayout(layout);

• To make Widget visible we have to use QWidget::show()

window->show();

Code Snippet

#include <QApplication>
#include <QPushButton>
#include <QVBoxLayout>
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QWidget window;
    window.resize(100,50);
    QVBoxLayout *layout=new QVBoxLayout();
    layout->addWidget(new QPushButton("Hello"));
    layout->addWidget(new QPushButton("Bye Bye"));
    window.setLayout(layout);
    window.show();
    return app.exec();
}