How to Use QPushButton: Difference between revisions

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=== Inherited from QAbstractButton ===
=== Inherited from QAbstractButton ===


* <tt>void clicked ( bool checked = false )</tt>
* <tt>void clicked(bool checked = false)</tt>
* <tt>void pressed ()</tt>
* <tt>void pressed()</tt>
* <tt>void released ()</tt>
* <tt>void released()</tt>
* <tt>void toggled ( bool checked )</tt>
* <tt>void toggled(bool checked)</tt>


=== Inherited from QWidget ===
=== Inherited from QWidget ===


* <tt>void customContextMenuRequested ( const QPoint &pos )</tt>
* <tt>void customContextMenuRequested(const QPoint &pos)</tt>


=== Inherited from QObject ===
=== Inherited from QObject ===


* <tt>void destroyed ( QObject * obj = 0 )</tt>
* <tt>void destroyed(QObject *obj = nullptr)</tt>


== Basic Usage ==
== Basic Usage ==
Line 45: Line 45:


<code>
<code>
connect(m_button, SIGNAL (released()),this, SLOT (handleButton()));
connect(m_button, &QPushButton::released, this, &MainWindow::handleButton);</code>
</code>


== Example ==
== Example ==
Line 69: Line 68:


=== mainwindow.h ===
=== mainwindow.h ===
<code>
<nowiki>
#ifndef MAINWINDOW_H
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QMainWindow>
#include <QMainWindow>
#include <QPushButton>
#include <QPushButton>
 
namespace Ui {
namespace Ui {
    class MainWindow;
  class MainWindow;
}
}
class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget *parent = 0);
private slots:
    void handleButton();
private:
    QPushButton *m_button;
};
   
   
#endif // MAINWINDOW_H
class MainWindow : public QMainWindow
</code>
{
  Q_OBJECT
public:
  explicit MainWindow(QWidget *parent = nullptr);
private slots:
  void handleButton();
private:
  QPushButton *m_button;
};
#endif // MAINWINDOW_H
</nowiki>


=== mainwindow.cpp ===
=== mainwindow.cpp ===
<code>
<nowiki>
#include "mainwindow.h"
#include "mainwindow.h"
 
#include <QCoreApplication>
MainWindow::MainWindow(QWidget *parent)
  : QMainWindow(parent)
MainWindow::MainWindow(QWidget *parent)
{
    : QMainWindow(parent)
  // Create the button, make "this" the parent
{
  m_button = new QPushButton("My Button", this);
    // Create the button, make "this" the parent
  // set size and location of the button
    m_button = new QPushButton("My Button", this);
  m_button->setGeometry(QRect(QPoint(100, 100), QSize(200, 50)));
    // set size and location of the button
    m_button->setGeometry(QRect(QPoint(100, 100),
    QSize(200, 50)));
   
   
    // Connect button signal to appropriate slot
  // Connect button signal to appropriate slot
    connect(m_button, SIGNAL (released()), this, SLOT (handleButton()));
  connect(m_button, &QPushButton::released, this, &MainWindow::handleButton);
}
}
   
   
void MainWindow::handleButton()
void MainWindow::handleButton()
{
{
    // change the text
  // change the text
    m_button->setText("Example");
  m_button->setText("Example");
    // resize button
  // resize button
    m_button->resize(100,100);
  m_button->resize(100,100);
}
}
</code>
</nowiki>


=== main.cpp ===
=== main.cpp ===
<code>
<nowiki>
#include "mainwindow.h"
#include "mainwindow.h"
#include <QApplication>
#include <QApplication>
   
   
int main(int argc, char *argv[])  
int main(int argc, char *argv[])  
{
{
    QApplication app(argc, argv);
  QApplication app(argc, argv);
    MainWindow mainWindow;
  MainWindow mainWindow;
    mainWindow.showMaximized();
  mainWindow.showMaximized();
    return app.exec();
  return app.exec();
}
}
</code>  
</nowiki>  


=== PushButtonExample.pro ===
=== PushButtonExample.pro ===
<code>
<nowiki>
QT      += core gui 
QT      += core widgets
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = PushButtonExample
TARGET = PushButtonExample TEMPLATE = app  
TEMPLATE = app  
SOURCES += main.cpp \ mainwindow.cpp   
SOURCES += main.cpp mainwindow.cpp   
HEADERS += mainwindow.h  
HEADERS += mainwindow.h  
</code>
</nowiki>

Latest revision as of 16:12, 29 November 2020

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Overview

Using QPushButton developers can create and handle buttons. This class is easy to use and customize so it is among the most useful classes in Qt. In general the button displays text but an icon can also be displayed.

QPushButton inherits QAbstractButton which in turn inherits QWidget.

Signals

Inherited from QAbstractButton

  • void clicked(bool checked = false)
  • void pressed()
  • void released()
  • void toggled(bool checked)

Inherited from QWidget

  • void customContextMenuRequested(const QPoint &pos)

Inherited from QObject

  • void destroyed(QObject *obj = nullptr)

Basic Usage

Text

The text of QPushButton can be set upon creation or using setText(). To get the current text of the button use text().

Icon

The icon of QPushButton can also be set upon creation. After creation the icon can be changed using setIcon() To get the current icon of the button use icon()

Set Position and Size

To set the position and the size of the button use setGeometry(). If you want just to modify the size of the button use resize()

Handle Button

QPushButton emits signals if an event occurs. To handle the button connect its appropriate signal to a slot:

connect(m_button, &QPushButton::released, this, &MainWindow::handleButton);

Example

The following simple code snippet shows how to create and use QPushButton. It has been tested on Qt Symbian Simulator.

An instance of QPushButton is created. Signal released() is connected to slot handleButton() which changes the text and the size of the button.

To build and run the example:

  1. Create an empty folder
  2. Create a file for each of the below code snippets and add the example code to them (the name of the file should match the name above the snippet).
    • All 4 files must be in the same folder.
  3. Using command line, navigate into the folder with the 4 files.
  4. run qmake on the project file:
    qmake PushButtonExample.pro
    
    • If successful it will not print any output.
    • This should create a file with the name Makefile in the folder.
  5. Build the application:
    make
    
    • The application should compile without any issues.
  6. Run the application:
    ./PushButtonExample
    

The above steps are for linux but can easily be followed on other systems by replacing make with the correct make call for the system.

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QPushButton>

namespace Ui {
  class MainWindow;
}
 
class MainWindow : public QMainWindow
{
  Q_OBJECT
public:
  explicit MainWindow(QWidget *parent = nullptr);
private slots:
  void handleButton();
private:
  QPushButton *m_button;
};
#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
  : QMainWindow(parent)
{
  // Create the button, make "this" the parent
  m_button = new QPushButton("My Button", this);
  // set size and location of the button
  m_button->setGeometry(QRect(QPoint(100, 100), QSize(200, 50)));
 
  // Connect button signal to appropriate slot
  connect(m_button, &QPushButton::released, this, &MainWindow::handleButton);
}
 
void MainWindow::handleButton()
{
  // change the text
  m_button->setText("Example");
  // resize button
  m_button->resize(100,100);
}

main.cpp

#include "mainwindow.h"
#include <QApplication>
 
int main(int argc, char *argv[]) 
{
  QApplication app(argc, argv);
  MainWindow mainWindow;
  mainWindow.showMaximized();
  return app.exec();
}
 

PushButtonExample.pro

QT       += core widgets
TARGET = PushButtonExample
TEMPLATE = app 
SOURCES += main.cpp mainwindow.cpp  
HEADERS += mainwindow.h