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Thread: Learning ActionListeners, help please.

  1. #1
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    Default Learning ActionListeners, help please.

    Alright, so I'm trying to learn how to make GUI's. I've managed to construct a frame, panel, menubars, items etc. Now I'm trying to get it so something happens when I click in the menu. I've followed a few different tutorials online, and also read through a textbook I bought. However, no matter what I try, I keep getting this error.

    Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
    	No enclosing instance of type RiskMain is accessible. Must qualify the allocation with an enclosing instance of type RiskMain (e.g. x.new A() where x is an instance of RiskMain).
     
    	at RiskMain.createWindow(RiskMain.java:43)
    	at RiskMain.main(RiskMain.java:34)


    the code is

    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
     
    import javax.swing.JFrame;
    import javax.swing.JMenu;
    import javax.swing.JMenuBar;
    import javax.swing.JMenuItem;
    import javax.swing.JOptionPane;
     
     
     
    public class RiskMain {
     
    	private static JFrame mainFrame = new JFrame("Risk Processor");
     
    	private static JMenuBar menuBar = new JMenuBar();
     
    	private static JMenu fileMenu = new JMenu("File");
    	private static JMenu gameMenu = new JMenu("Game");
    	private static JMenu playerMenu = new JMenu("Player");
     
     
     
    	private static JMenuItem newGame = new JMenuItem("New");
    	private static JMenuItem openGame = new JMenuItem("Open");
    	private static JMenuItem saveGame = new JMenuItem("Save");
    	private static JMenuItem quitGame = new JMenuItem("Quit");
    	private static JMenuItem newDay = new JMenuItem("New Day");
    	private static JMenuItem genText = new JMenuItem("Generate Text");
    	private static JMenuItem addAttack = new JMenuItem("Add Attack");
    	private static JMenuItem purchItem = new JMenuItem("Purchase Item");
     
        public static void main(String []args) {
     
        	createWindow();
     
        }
        public static void createWindow() {
        	menuBar.add(fileMenu);
        	menuBar.add(gameMenu);
        	menuBar.add(playerMenu);
     
        	fileMenu.add(newGame);
        		newGame.addActionListener(new MenuItemListener()); 
        	fileMenu.add(openGame);
        	fileMenu.add(saveGame);
        	fileMenu.add(quitGame);
     
        	gameMenu.add(newDay);
        	gameMenu.add(genText);
     
        	playerMenu.add(addAttack);
        	playerMenu.add(purchItem);
     
        	mainFrame.setJMenuBar(menuBar);
     
        	mainFrame.setVisible(true);
        	mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        	mainFrame.setSize(1200,800);
     
        }
     
        private class MenuItemListener implements ActionListener {
     
        	public void actionPerformed(ActionEvent e) {
        		JOptionPane.showMessageDialog(null, "click");
     
        	}
        }  
    }

    I appreciate any help and incite that can be offered.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Learning ActionListeners, help please.

    A couple of solutions:
    1)Move the code out of the static method into an instance method in the RiskMain class.
    2)Make the MenuItemListener class static so it exists without needing an instance of the RiskMain class.
    3)Use the technique described in the error message.
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
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    Default Re: Learning ActionListeners, help please.

    Move which code out?

    Also, I don't understand what the error message is telling me to do. What does it mean by qualifying the allocation with an enclosing instance?

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: Learning ActionListeners, help please.

    Make the createWindow() method an instance method NOT static.

    The MenuItemListener class belongs to the RiskMain class. You need to create an instance of the RiskMain class to use to create an instance of the MenuItemListener class.
    If you don't understand my answer, don't ignore it, ask a question.

  5. #5
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    Default Re: Learning ActionListeners, help please.

    Quote Originally Posted by Norm View Post
    Make the createWindow() method an instance method NOT static.

    The MenuItemListener class belongs to the RiskMain class. You need to create an instance of the RiskMain class to use to create an instance of the MenuItemListener class.
    Ah, okay, that makes sense. I have to go for now, so I can't give it a try just yet, but I'll give it a go later today and post back my success/failure. Thanks for your help so for

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