Get my Actions to see my other objects

Question

I have a JLabel that has keybinded actions on it. I have defined some code for some of the Actions but, alas, there are other JLabels, a JPanel, and other things within the method (this is in main()) that I want my Actions to fool with.

I tried to change the Actions into taking parameters, but was not successful, how can I get my actions to take in parameters to manipulate? Is there any way? I have looked about but this is pretty specific and I see few good examples.

Here is a nice slab of my code:

    /*Bunch of stuff I want my actions to interact with above - another JLabel, a JPanel*/
    ImageIcon cursor = new ImageIcon("cursor.gif");
    JLabel cursorlbl = new JLabel("", cursor, JLabel.CENTER);
    Action goRight = new AbstractAction() {

        @Override
        public void actionPerformed(ActionEvent arg0) {
            System.out.println("lol");

        }
    };

    Action goLeft = new AbstractAction() {

        @Override
        public void actionPerformed(ActionEvent arg0) {
            System.out.println("lol2");
        }
    };

    Action goUp = new AbstractAction() {

        @Override
        public void actionPerformed(ActionEvent arg0) {


        }
    };

    Action goDown = new AbstractAction() {

        @Override
        public void actionPerformed(ActionEvent arg0) {
            System.out.println("lol2");

        }
    };


    cursorlbl.setFocusable(true);
    cursorlbl.getInputMap().put(KeyStroke.getKeyStroke("RIGHT"),
            "pressed right");
    cursorlbl.getInputMap().put(KeyStroke.getKeyStroke("LEFT"),
            "pressed left");
    cursorlbl.getActionMap().put("pressed right", goRight);
    cursorlbl.getActionMap().put("pressed left", goLeft);

score 2 · Accepted Answer · answered Jul 12 '12 at 21:50

You can declare each action as a subclass (this starts to separate MVC anyways), and each item you want to manipulate a field in the parent class. Example:

// Parent Class
public class ParentClass{
//Field you want to mess with in your action
   JLabel cursorlbl = new JLabel("");

    // Action that does things
    public class MoveAction extends AbstractAction{
        char direction;

        //Constructor for action
        public MoveAction(char direction){
            this.direction = direction;
        }

        @Override
        public void actionPerformed(ActionEvent arg0) {
            int change = 0;

            // Figure out how you'll be changing the variable
            if(direction == 'u' || direction == 'r'){
                change = 1;
            } else{
                change = -1;
            }

            // Apply the change to the correct variable
            if(direction == 'u' || direction =='d'){
                cursy += change;
            } else{
                cursx += change;
            }

            //Example how you can access the parent class's fields
            cursorlbl.setLocation(cursx, cursy);
        }       
    }
}

Then to set your actions, you just create instances of your subclass:

    contentArea.getActionMap().put("pressed right", new MoveAction('r'));
    contentArea.getActionMap().put("pressed left", new MoveAction('l'));

score 0 · Answer 2 · answered Jul 12 '12 at 17:35

0

Declare other components you wish to see in your actions as final. That will make actions see them.

More info here

answered Jul 12 '12 at 17:35

ioreskovic

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score 0 · Answer 3 · answered Jul 12 '12 at 17:36

You should be able to pass them in like this:

// note that the JLabel is now final
final JLabel cursorlbl = new JLabel("", cursor, JLabel.CENTER);
Action goRight = new AbstractAction() {

    @Override
    public void actionPerformed(ActionEvent arg0) {
        System.out.println(cursorlbl.getText()); // has access to JLabel because it's scoped to the method/class

    }
};

Note that doing this can cause some maintenance issues and you should try to document things that might be unclear for future developers (and yourself two weeks from now!)

Get my Actions to see my other objects

3 Answers3