I'm trying to separate components of my Java desktop app into different classes. For example, I have a MenuBar class, called from the MainClass, that creates the JMenuBar.
Normally, I would implement ActionListener in the MenuBar class and override actionPerformed() to keep everything organized. But if I do that, how can I let the MainClass know what was clicked?
I tried implementing my own ActionListener, but I couldn't come up with a solution that was capable of dispatching events to other classes.
MainClass.java
public class MainClass extends JFrame {
private static void createAndShowGUI() {
JFrame.setDefaultLookAndFeelDecorated(false);
JFrame frame = new JFrame("Main Window");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
MenuBar menuBar = new MenuBar();
JMenuBar mb = menuBar.createMenu();
frame.setJMenuBar(mb);
frame.setSize(400,400);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
MenuBar.java
public class MenuBar implements ActionListener {
public JMenuBar createMenu() {
JMenu menu;
JMenuItem item;
JMenuBar menuBar = new JMenuBar();
menu = new JMenu("Main");
menuBar.add(menu);
item = new JMenuItem("New");
menu.add(item);
return menuBar;
}
@Override
public void actionPerformed(ActionEvent e) {
JMenuItem source = (JMenuItem)(e.getSource());
System.out.println("Action triggered on: "+source.getText());
// *** Let MainClass know what was clicked ??
}
}
EDIT
I realized I can just create an ActionListener in the MainClass and pass that to the MenuBar class, like this:
Amended MainClass.java
ActionListener l = new ActionListener() {
public void actionPerformed(ActionEvent ae) {
System.out.println(ae.getActionCommand());
}
};
MenuBar menuBar = new MenuBar();
frame.setJMenuBar(menuBar.createMenu(l));
And then, in MenuBar, I just apply the ActionListener to each of the menu items.
Amended MenuBar.java
public JMenuBar createMenu(ActionListener l) {
item = new JMenuItem("Hide When Minimized");
item.addActionListener(l);
menu.add(item);
}
One possible solution is MainClass implements ActionListener
and pass its instance to MenuBar.createMenu():
public class MenuBar {
public JMenuBar createMenu( ActionListener l ) {
...
menuItem.addActionListener( l );
}
...
}
MainClass side:
public class MainClass extends JFrame {
@Override
public void actionPerformed(ActionEvent e) {
Object source = e.getSource();
System.out.println( "Action triggered by: " + source );
}
private static void createAndShowGUI() {
...
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
MenuBar menuBar = new MenuBar();
JMenuBar mb = menuBar.createMenu( frame );
frame.setJMenuBar( mb );
...
}
}
Another way is to use java.beans.PropertyChangeListener and java.beans.PropertyChangeSupport
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