[Code Sharing] Detecting Key being held down

cocos2d-x C++
#1

Hi people. I have 3 days with Coco2d and 3 days with games programming. The first problem I found while programming with cocos was that there was no event to detect a key being held down. Searching the forum and google I found a couple of solutions, well, not really, I found just one solution from “Game from Scratch”. It is a bit overcomplicated so I decided to share my solution, so the next time somebody have the same problem, they can use the searching tool and find this. I saw that the KeyCode was an enum, and every key corresponded to an integer number as in the Ascii code. That is why I created an array of 255 positions. If you see any problem feel free to reply and fix my code. Here it goes.

Declare an array as a private field in your class:

	boolean keys[255] = { false };

Implement some lambdas for the events, in the init method of your class, as follows:

	keyboardListener->onKeyPressed = [&](EventKeyboard::KeyCode code, Event* event) {
		keys[(int)code] = true;
	};
	keyboardListener->onKeyReleased = [&](EventKeyboard::KeyCode code, Event* e) {
			keys[(int)code] = false;
	};
	this->_eventDispatcher->addEventListenerWithSceneGraphPriority(keyboardListener, pad);

Check for the keys you want to use, in the main loop:

void HelloWorld::update(float delta) {
	
	if (keys[(int)EventKeyboard::KeyCode::KEY_LEFT_ARROW]) {
		pad->setPosition(pad->getPosition().x - 1 * speed * delta, pad->getPosition().y);
	}

	if (keys[(int)EventKeyboard::KeyCode::KEY_RIGHT_ARROW]) {
		pad->setPosition(pad->getPosition().x + 1 * speed * delta, pad->getPosition().y);
	}

That’s it, cheers and till the next time

2 Likes
Key held and update pointer problem
#2

can i use this in our docs?

#3

Yes ofcourse you can sir! feel free to use or modify it the way you want.

#4

Well, this is quite a simple solution to implement yourself as to why there isn’t a built in one I guess. At least make the thing a map of cocos2d::EventKeyboard::KeyCode and bool so you can actualy look up what keys are pressed if you need to.

For reference (as this is “code-sharing”) I have a similar solution built inside my CCX library that you can just attach to any node and capture any keyboard events. You can find it in the input section.

#5

Thank you, crugthew, yeah, there is nothing funcy with my code, i am not blaming cocos neither, its an awesome and powerfull framework. i didn’t wanted to make it with a map, because i wanted to keep it simple, very simple, since its going to be read by newcomers mostly, and at some point its quicker than a map, in my use case, O(1) Vs O(log n). But yeah, if i want to know if A && B are being pressed i just have to check 2 conditions in O(1) time, it works for multiple keys at the same time.

I will check your library, thank you again