Qt vs. Swing
| Qt | Swing | |
|---|---|---|
| Class name | Qxxxx |
Jxxxx |
| Writing the "GUI" class | Assume the following class declaration GUI.h
#include <qmainwindow.h>
class GUI : public QMainWindow {
public:
GUI ();
}
and the corresponding function definition in GUI.cc
GUI::GUI ()
{
setWindowTitle ("Simple Qt Window");
}
|
The following is written in GUI.java
import javax.swing.JFrame;
public class GUI extends JFrame {
public GUI ()
{
setTitle ("Simple Swing Window");
}
}
|
The main() function |
#include <qapplication.h>
int main (int argc, char* argv[]) {
{
QApplication myApp(argc, argv);
GUI myGUI;
myGUI.show();
return a.exec();
}
|
public static void main (String[] args) {
{
GUI myGUI = new GUI();
myGUI.setVisible (true);
}
|
| Layout Manager |
GUI::GUI (QWidget *parent, const char *name)
{
/* create a vertical box layout for this widget */
QVBoxLayout *p = new QVBoxLayout ();
QPushButton *b1 = new QPushButton ("Go");
QPushButton *b2 = new QPushButton ("Go");
p->addWidget (b1);
p->addWidget (b2);
}
|
public GUI ()
{
JPanel p;
p = new JPanel();
/* create a vertical box layout */
BoxLayout vert = new BoxLayout (contPane,
BoxLayout.Y_AXIS);
p.setLayout (vert);
JButton b1 = new JButton ("Go");
JButton b2 = new JButton ("Stop");
p.add (b1);
p.add (b2);
}
|
| Menubar |
QMenuBar *mb = new QMenuBar (this);
setMenuBar (mb);
QMenu *file = new QMenu (mb);
QAction *exit = new QAction();
exit.setText ("Exit");
file->addAction (exit);
|
JMenubar mb = new JMenubar();
setJMenubar (mb);
JMenu file = new JMenu ("File");
mb.add (file);
JMenuItem exit = new JMenuItem ("Exit");
file.add (exit);
|
Event Handling
Swing implements its event handling mechanism via its event and listener objects. Any user action to a GUI component may result in an event object generated and sent to its listener(s).
In Qt, a similar mechanism is implemented via signals and slots. Any user action to a GUI component (Qt widget) may result in a signal "generated" and sent to its associated slot(s). In short:
Swing events are analogous to Qt signals
Swing listeners are analogous to Qt slots
Swing listeners are analogous to Qt slots
However, Qt signal-slot mechanism is more flexible than Swing event-(event listener) mechanism since Qt allows us to define our own signals.
| Swing - Java | Qt - C++ |
|---|---|
Assume the following code segment in Java to handle mouse clicks on a JButton
ActionListener myHandler = new MyBtnHandler();
JButton go = new JButton ("Go");
go.addActionListener (myHandler);
and the class MyBtnHandler:
private class MyBtnHandler implements ActionListener
{
public void actionPerformed (ActionEvent a)
{
/* this method gets called when the go button is clicked */
}
}
|
In Qt, the code is more straight forward:
QPushButton *go = new QPushButton ("Go");
connect (go, SIGNAL(clicked()), this, SLOT(myAction()));
Assuming myAction() is a function in this class (GUI.cc):
void GUI::myAction()
{
/* this function gets called when the go button is clicked */
}
In the header file (GUI.h) the function myAction() must be declared as a slot:
class GUI : public QWidget {
// other stuff not shown
public slots:
void myAction();
// other stuff not shown
}
|
The Qt online documentation provides a more comprehensive reading materials on signals and slots.