Using multiple keys in Qt C++

c++, qt

Solution

You can add a pressed key to the set of pressed keys and remove from this set when the key is released. So you can add the pressed key to a QSet which is a class member :

QSet<int> pressedKeys;

You can catch the key events in an event filter :

bool MyWidget::eventFilter(QObject * obj, QEvent * event)
{

    if(event->type()==QEvent::KeyPress) {

        pressedKeys += ((QKeyEvent*)event)->key();

        f( pressedKeys.contains(Qt::Key_Up) && pressedKeys.contains(Qt::Key_Left) )
        {
            // up and left is pressed
        }

    }
    else if(event->type()==QEvent::KeyRelease)
    {

        pressedKeys -= ((QKeyEvent*)event)->key();
    }


    return false;
}

Don't forget to install the event filter in the constructor:

this->installEventFilter(this);

Problem

I'm building the "Tanks" game where I'm using Key event to run my tank on map. Actually I can only use one key at the time but I need to have ability to f.e. go up and left simultaneously. Here's my code for single key events: ``` switch(event->key()) { case Qt::Key_Up: if(!ui->widget->playerList[playerID]->canMove(0.3, 20, 20, -20, -20, 1.5)) return; ui->widget->playerList[playerID]->move(0.3); ui->widget->updateGL(); break; case Qt::Key_Down: if(!ui->widget->playerList[playerID]->canMove(-0.2, 20, 20, -20, -20, 1.5)) return; ui->widget->playerList[playerID]->move(-0.2); ui->widget->updateGL(); break; case Qt::Key_Right: ui->widget->playerList[playerID]->rotate(10); ui->widget->updateGL(); break; case Qt::Key_Left: ui->widget->playerList[playerID]->rotate(-10); ui->widget->updateGL(); break; case Qt::Key_Q: ui->widget->playerList[playerID]->rotateCannon(10); ui->widget->updateGL(); break; case Qt::Key_E: ui->widget->playerList[playerID]->rotateCannon(-10); ui->widget->updateGL(); break; default: QMainWindow::keyPressEvent(event); break; } ```

Original source