Toggling a boolean with KeyListeners and MouseListeners

Question

I'm writing a simple program to practice my GUI skills, but I've encountered a problem. I want my program to do something when the ALT key is pressed, and the mouse is clicked. I have a boolean that is set to TRUE in the keyPressed method, and FALSE in the keyReleased method. When I call the mouseClicked method, the boolean is FALSE, even if it is being set to TRUE by the key methods.

Here is keyListener the code:

  private boolean altPressed;

        //......

    @Override
        public void keyPressed(KeyEvent e) {

        int keyCode = e.getKeyCode();

        if(keyCode == KeyEvent.VK_ALT){
            altPressed = true;
            System.out.println("ALT pressed. ALT: "+altPressed);
        }

    }

    @Override
    public void keyReleased(KeyEvent e) {

        int keyCode = e.getKeyCode();

        if(keyCode == KeyEvent.VK_ALT){
            altPressed = false;
            System.out.println("ALT released. ALT: "+altPressed);
        }
    }

and the MouseListener code:

@Override
    public void mouseClicked(MouseEvent e) {

        int keyCode = e.getButton();

        if(keyCode == MouseEvent.BUTTON1){
            System.out.println("MOUSE button 1 pressed. ALT: "+altPressed);

        }

    }

Console output (with some commentary)

ALT pressed. ALT: true               //I'm pressing and holding ALT
ALT pressed. ALT: true
MOUSE button 1 pressed. ALT: false   //Clicking the mouse
ALT pressed. ALT: true
ALT pressed. ALT: true
ALT released. ALT: false             //releasing ALT

Why is the boolean false, even though it is being set to true by the KeyListener method? Hopefully, I'm not missing somehting really obvious. Thanks for helping!

How are you using this Listener class? If you have two instances of this class, you can't expect to use the variable `altPressed` across multiple instances. I reckon you are using multiple instances of this class for which `altPressed` variable is initialized to `false` (default in java) — Kaushal Niraula, Jun 21 '17 at 21:39
[This](https://stackoverflow.com/questions/43238705/how-to-assign-a-shortcut-key-combination-to-a-javafx-dialog) may help. You need to look at Key combinations. — SedJ601, Jun 21 '17 at 21:48
@KaushalNiraula Yeah, I have one class that implements both Key and Mouse listeners, and I did something like this: list.addKeyListener(new Main()); list.addMouseListener(new Main()); So I had two copies of the boolean... I changed it to static, it works like a charm now, thanks! — SomeDude123, Jun 21 '17 at 21:49
Oh, not JavaFx, Sorry. It's probably the same idea for awt and/or Swing. — SedJ601, Jun 21 '17 at 21:49
You need to to store that flag somewhere else if you want to use it across different instances. Maybe in a different variable outside of that listener class(you would need to take care of synchronization obviously) — Kaushal Niraula, Jun 21 '17 at 21:53

Toggling a boolean with KeyListeners and MouseListeners

0 Answers0