Question

I’m developing a shoot’em up with qt creator and my problem is the link with the keyPressEvent function of my scene:

void Scene::keyPressEvent(QKeyEvent *event){
    liste_event << event->key();

    if (liste_event.contains(Qt::Key_Left)) {
        vaisseau->MoveX(-1);
    }

    if (liste_event.contains(Qt::Key_Right)) {
        vaisseau->MoveX(1);
    }
}

It compiles, but my sprite (vasisseau) moves very slowly. How can I improve the code so it moves faster?

Answer 1

Well, the problem is that you are leaving the animation of the game to the keyPressEvent, which is not triggered as often as you would like.

To solve this problem I suggest you use the traditional approach, which involves having an function to draw() the scene (and it’s objects). The idea is that this function is called every X miliseconds, and the drawing will work independently of a key being pressed or not.

So in this case, inside keyPressEvent you would just store the key that was pressed, and in Scene::draw() you will implement the logic that will call MoveX() with the appropriate parameter, based on the stored key.