Re: How to use actionListers within static methods
"Ian Wilson" <scobloke2@infotop.co.uk> wrote in message
news:NIGdnXAhP5kBOPnZRVnyjw@bt.com...
In the code below I am attempting to define an ActionListener for a button
so I can do something useful when the button is pressed.
At the statement
ButtonListener buttonListener = new ButtonListener();
Eclipse says "No enclosing instance of type Hats is accessible, Must
qualify the allocation with an enclosing instance of type Hats (e.g. x.new
A() where x is an instance of Hats".
The trouble is I never intend to instantiate Hats since I don't ever
expect to need multiple Hats objects in existence at the same time.
Q.1 Is there a fix?
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class StaticGUI {
public static JFrame frame = new JFrame();
public static void main(String[] args) {
// main GUI with menu that invokes ...
Hats.editHats();
}
}
class Hats {
// so can refer to addButton in buttonListener:
public static JButton addButton;
public static void editHats() {
addButton = new JButton("Add");
JButton editButton = new JButton("Edit");
JButton removeButton = new JButton("Remove");
ButtonListener buttonListener = new ButtonListener();
addButton.addActionListener(buttonListener);
editButton.addActionListener(buttonListener);
removeButton.addActionListener(buttonListener);
JPanel buttonPanel = new JPanel();
buttonPanel.add(addButton);
buttonPanel.add(editButton);
buttonPanel.add(removeButton);
JPanel panel = new JPanel();
panel.setLayout(new BoxLayout(panel, BoxLayout.PAGE_AXIS));
JTextArea textArea = new JTextArea();
panel.add(textArea);
panel.add(buttonPanel);
JOptionPane pane = new JOptionPane(
panel, // "message"
JOptionPane.PLAIN_MESSAGE, // messagetype
JOptionPane.OK_CANCEL_OPTION // optiontype
);
JDialog dialog = pane.createDialog(StaticGUI.frame,"Test");
dialog.setResizable(true);
dialog.setVisible(true);
} // method editHats
// an inner class within Hats, to listen to Hat-related button events
class ButtonListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
JComponent c = (JComponent) e.getSource();
if (c == addButton) {
System.out.println ("You pressed 'Add'");
}
}
}
} // class Hats
Q.2 should I rethink my whole approach to my design of this application?
You should rethink your approach.
You make all Hats methods static because you never intend to instantiate
Hats since don't expect to need multiple Hats objects in existence at the
same time.
First, if it is static, you never have even one object...
Second, that's not really a good reason to make the class static.
But Hats does instantiate a JDialog, so why not just make Hats
the JDialog itself? And have it implement ActionListener, so you
don't have to have inner classes:
public class Hats extends JDialog implements ActionListener {
// constructor
public Hats() {
// Create buttons, panels, etc.
...
// set up ActionListener
addButton.addActionListener( this );
editButton.addActionListener( this );
removeButton.addActionListener( this );
}
// ActionListener method
public void actionPerformed( ActionEvent e ) {
// body here
}
}