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swing VS QT

2015-10-16 22:21 423 查看

Qt vs. Swing

QtSwing
Class name
Qxxxx
Jxxxx
Writing the "GUI" classAssume 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
However, Qt signal-slot mechanism is more flexible than Swing event-(event listener) mechanism since Qt allows us to define our own signals.

Swing - JavaQt - 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.
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