Processing 1.0 - Processing Discourse - Multiple keys pressed simultaneously

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Index › Programming Questions & Help › Syntax Questions › Multiple keys pressed simultaneously

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Multiple keys pressed simultaneously (Read 891 times)

Oolong Junior Member Offline Posts: 87 Scotland	Multiple keys pressed simultaneously Nov 26^th, 2007, 9:18pm Hello, Maybe I'm being dense, but I can't see a way to detect multiple key presses at the same time! I was going to write a little game, but it's going to be tricky if I can't do this...! Thanks - f.
	http://oolong.co.uk/play

JohnG

Re: Multiple keys pressed simultaneously
Reply #1 - Nov 26^th, 2007, 9:45pm

I've no idea if it's possible to detect multiple keypressed if they happen all at the same time, but most of the time they're actually multiple seperate (though concurrent) presses, and you can track that. Or processing is clever enough to run keyPressed once per key...

All you need to do is keep an array of boolean values, one per key, and set the value for a particular key to true when it's pressed (in keyPressed()) and false when it's released (in keyReleased())

extrapixel Full Member Offline Posts: 210 Switzerland	Re: Multiple keys pressed simultaneously Reply #2 - Nov 27^th, 2007, 1:36am and, unfortunately, new keyboards often can't handle more than 2-3 simultanious keypresses (+modifier keys).
	http://www.extrapixel.ch

extrapixel

Re: Multiple keys pressed simultaneously
Reply #3 - Nov 27^th, 2007, 2:16am

Quote:

int nrKeys = 0;
PFont font;
boolean[] downKeys = new boolean[256];

void setup() {
size(200,200);
fill(255);
font = createFont("Courier", 20);
textFont(font);
}

void draw() {
background(0);
nrKeys = 0;
for (int i=0; i<downKeys.length; i++) {
if (downKeys[i]) {
nrKeys++;
text((char)i, 10*nrKeys,height/2);
}
}
text("Nr. of Keys: " + nrKeys, 20,20);
}

void keyPressed() {
println(key);
if (key<256) {
downKeys[key] = true;
}
}

void keyReleased() {
if (key<256) {
downKeys[key] = false;
}
}

it's weird... on my macbook pro i can *sometimes* get 5 simultanious keys. it seems like this keyboard has some strange wiring. With some combinations I can't get over 3.
or is it my script?

http://www.extrapixel.ch

Oolong

Re: Multiple keys pressed simultaneously
Reply #4 - Nov 28^th, 2007, 11:41pm

Thanks guys! Yeah, keyReleased makes a lot of sense.

Extrapixel, for what it's worth I've noticed this thing in the past of keyboards only registering a given number of keys at once, *and* that number depending on which keys are being pressed. Very weird, but I think I first noticed it on a ZX Spectrum back in the 80s!

http://oolong.co.uk/play

Oolong Junior Member Offline Posts: 87 Scotland	Re: Multiple keys pressed simultaneously Reply #5 - Nov 29^th, 2007, 7:02pm Wait, hold on. How do I know which key has been released? The key variable just tells us which key was most recently pressed, so if someone was holding down more than one key, it's not much use to us, right?
	http://oolong.co.uk/play

JohnG Ex Member	Re: Multiple keys pressed simultaneously Reply #6 - Nov 29^th, 2007, 7:29pm In keyReleased 'key' is the most recently released key.

Oolong Junior Member Offline Posts: 87 Scotland	Re: Multiple keys pressed simultaneously Reply #7 - Nov 30^th, 2007, 12:57pm Oh! Okay, thanks John. Is that documented anywhere?! I guess it'll work for keyCode too, right?
	http://oolong.co.uk/play

fry YaBB Moderator Offline Posts: 2623 mass, usa	Re: Multiple keys pressed simultaneously Reply #8 - Nov 30^th, 2007, 2:16pm http://processing.org/reference/key.html

JohnG Ex Member	Re: Multiple keys pressed simultaneously Reply #9 - Nov 30^th, 2007, 3:12pm Unfortunately, I've just noticed that the reference for key say specifically "he system variable key always contains the value of the most recently pressed key" and I think that's not entirely true, since it's the most recently 'changed state' key I believe.

fry YaBB Moderator Offline Posts: 2623 mass, usa	Re: Multiple keys pressed simultaneously Reply #10 - Nov 30^th, 2007, 3:37pm yes, you're correct. i've updated the reference for the next release.

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