Question

Following on from this question, I have a menu system as follows:

MainMenu > (Load Game button clicked) > LoadGameMenu
LoadGameMenu > (Back To Main Menu button clicked) > MainMenu
LoadGameMenu > (Load button clicked) > GameScreen

However, when I click on the Load button, the MainMenu is shown instead. Here’s my code:

ApplicationWindow::ApplicationWindow()
{
    resize(800, 600);

    stack = new QStackedWidget(this);
    signalMapper = new QSignalMapper(this);

    mainMenu = new MainMenu(this);
    loadGameMenu = new LoadGameMenu(this);
    gameScreen = new GameScreen(this);

    stack->addWidget(mainMenu);
    stack->addWidget(loadGameMenu);
    stack->addWidget(gameScreen);

    connect(mainMenu, SIGNAL(loadGameClicked()), signalMapper, SLOT(map()));
    connect(loadGameMenu, SIGNAL(backToMainMenuClicked()), signalMapper, SLOT(map()));
    connect(loadGameMenu, SIGNAL(loadClicked()), signalMapper, SLOT(map()));

    signalMapper->setMapping(loadGameMenu, 0);
    signalMapper->setMapping(mainMenu, 1);
    signalMapper->setMapping(gameScreen, 2);

    connect(signalMapper, SIGNAL(mapped(int)), stack, SLOT(setCurrentIndex(int)));

    setCentralWidget(stack);
}

I know I’m doing something wrong with the signal mapping, but I don’t know what it is.

Cheers.

Answer 1

1) QSignalMapper maps a QObject* sender to a (int, string, QWidget* or QObject*). Since your “load” and “return to main menu” signals are being sent from the same sender object they will be mapped the same way. The solution is to connect the clicked signal of the different buttons to the mapper directly (rather than through your LoadGameMenu object), so the sender is different.

2) Since you’re using a QStackedWidget, I would strongly consider using the QWidget* mapping of QSignalMapper, and connect to QStackedWidget::setCurrentWidget. This will be easier to maintain if/when you add more menu screens, rather than trying to keep up with which int index is which widget. It also makes things more readable in your code, in my opinion.

Edit: Looks like you’re not understanding the setMapping function. I’d take a look at the docs for better a better idea. What you’re doing there is mapping the first argument (the sender) to a signal to be sent (the second argument). In your original code, you’re mapping LoadGameMenu to 0. Any time a signal is sent to the mapper from LoadGameMenu, 0 is sent to stackedWidget::setCurrentIndex` – which is why both buttons are returning you to the same place.