More then 5 key-presses?

Question

Hi there,
I'm trying to re-create a game that me and my friends have been playing quite a lot in the last few weeks. The game is called Kurve, and it's an offline multiplayer game. Up to six players can play the game on one keyboard.
The idea of the game is this:
Each player get's a snake and two keys. The snake moves around and the player has to steer the snake around using these two keys and try to survive as long as possible, without colliding with other snakes.
Now my problem:
I've got the base engine working, snakes can move around with any key they want, collisions are beiging checked etc. But when doing some extra testing I noticed that, when I press 4 random keys on my keyboard, I couldn't press any other keys.
This, however, is something that's important for the game and needs to be fixed if I'd ever want to release it.
I'm currently doing keypresses in the folowing way:
- implementing the KeyListener
- storing each key-presssed-code in a HashSet
- removing each key-released-code from the Hashset
- whe excecuting a step; checking if the HashSet containt a steering key for a snake
I hope I'm clear enough and that someone can help me.
~Sph
Message was edited by:
sph
Message was edited by:
sph

Answer 1

I found a great page about this phenomenon a while back, unfortunately I've lost track of it. The basic problem you're having is that keyboards are not, in general, designed for gaming. They're designed for typing, which means the developers can cut corners to save some cash by making assumptions; mainly that you won't be pressing many keys at once. Aside from the metakeys (Ctrl,Shift,Alt), the keyboard is wired into one or more grids of keys. Each key within the grid activates both the horizontal and vertical wire underneath it, and with the two wires the grid can determine which key was pressed. Consider this small arrangement of keys:
||
-AB-1
-CD-2
||
34Any individual key is easily identified, A=1&3, B=1&4, C=2&3, D=2&4. Two keys is a little trickier, but still doable. If A is held, B will activate 4, C will activate 2, and D will activate both 2 and 4. So we can still tell which two keys were pressed. At three keys, we have a problem. If A and D are pressed, all wires are already active, so pressing B or D won't accomplish anything. If, on the other hand, B is pressed, pressing either C or D will activate wire 2. This is more information, but still not enough. They keyboard can tell that either C or D was pressed, but not which. So any combination of two held keys and a third press either isn't be detected or is confusing, the keyboard can't tell what input it's getting. So it refuses to give any new output, except an error.
I'm afraid you've hit one of the problems that's been annoying gamers for years. The only real solution is to either explore and find out what combos are OK on your keyboard, or try and find a manufacturer who makes a better one. In the latter case, you might look at someone who makes keyboards specifically for gamers, they're more likely to alow multiple presses (but check first!). You'll probably end up paying a premium for it, but you may decide that's worth it to you.
-FM