KeyEvent not firing when certain other keys are pressed

Question

I'm having more key problems in Java. The SPACE Key event works just fine by itself, and when other keys are being pressed...

But if I press down the UP key and the LEFT key at the same time the SPACE event does not fire. However the SPACE does fire when if LEFT or UP are pressed alone or with other keys.

Here's my code:

public void keyPressed(KeyEvent e) 
{
    if(e.getKeyCode() == KeyEvent.VK_UP)
    {
        upkeyisdown = true;         
    }
    if(e.getKeyCode() == KeyEvent.VK_DOWN)
    {
        downkeyisdown = true;
    }
    if(e.getKeyCode() == KeyEvent.VK_LEFT)
    {
        leftkeyisdown = true;
    }
    if(e.getKeyCode() == KeyEvent.VK_RIGHT)
    {
        rightkeyisdown = true;
    }
    if(e.getKeyCode() == KeyEvent.VK_SPACE)
    {
        spacekeyisdown = true;
    }

}  
public void keyReleased(KeyEvent e) 
{
    if(e.getKeyCode() == KeyEvent.VK_UP)
    {
        upkeyisdown = false;            
    }

    if(e.getKeyCode() == KeyEvent.VK_DOWN)
    {
        downkeyisdown = false;
    }
    if(e.getKeyCode() == KeyEvent.VK_LEFT)
    {
        leftkeyisdown = false;
    }
    if(e.getKeyCode() == KeyEvent.VK_RIGHT)
    {
        rightkeyisdown = false;
    }
    if(e.getKeyCode() == KeyEvent.VK_SPACE)
    {
        spacekeyisdown = false;
    }
}

Possible duplicate of [KeyListener not being triggered after I swap JPanels](http://stackoverflow.com/questions/5067906/keylistener-not-being-triggered-after-i-swap-jpanels) or [How can a KeyListener detect key combinations (e.g., ALT + 1 + 1)](http://stackoverflow.com/q/7851505/230513) or [Java KeyLister: How to perform an action when two keys are pressed?](http://stackoverflow.com/q/10655010/230513) — trashgod, Jun 30 '12 at 00:00
No, my problem is similar but those articles were not helpful. — Joe, Jun 30 '12 at 01:46

score 3 · Answer 1 · edited May 23 '17 at 10:26

As noted in KeyEvent, there is no support for multiple simultaneous KEY_PRESSED or KEY_RELEASED events. The same applies to KeyStroke. You can bind to instances of KeyStroke that include modifiers, as shown here. Modifiers may include "alt, shift, control, meta, altGraph, or a combination thereof."

Addendum: "If I press down the UP key and the LEFT key at the same time, the SPACE event does not fire."

Using the KeyEventDemo from How to Write a Key Listener, I see the expected KEY_PRESSED and KEY_RELEASED events. The order varies because the events can't actually occur "at the same time," although KEY_PRESSED reliably precedes KEY_RELEASED. I suspect a logic error elsewhere in your code. One way to manage the complexity is to

Use an enum to hold keyCodes; this game uses single keystrokes, but it illustrates how to use an an enum in this context.
Use EnumSets to contain recognized combinations; there's a related example here.

Well, by using the booleans I have a sort of multi-keypress system. This system works great, it's just being funky with the combo of UP, LEFT, and SPACE....but all other combos work. — Joe, Jul 01 '12 at 01:54

KeyEvent not firing when certain other keys are pressed

1 Answers1