CardLayout get the selected card's name

Question

How can I get the string identifier of the selected panel in card layout.

Suziesuzuki

Answer 1

The CardLayout does not know what the currently selected panel is. You should keep this in memory yourself, when calling the show() method.

Katrinka

+1 Here's a related example. – Foxe

that's ok. is it a feature we should ask to swing team? the fact that in java 7 they've released a new component for swing (the JLayer) suggests that oracle will at least keep swing in maintenance. so why not add useful features like this one? – Landers

Answer 2

The CardLayout does not allow you to do this. However, you should be able to access the top panel of the CardLayout.

So a little work around is to give each added panel a name, equal to the string identifier. That way you can get the top card, and get it's name. This is how you do it:

final String CARD1 = "Card 1";
final String CARD2 = "Card 2";

JPanel panel = new JPanel(new CardLayout());
JPanel card1 = new JPanel();
card1.setName(CARD1);
JPanel card2 = new JPanel();
card2.setName(CARD2);

panel.add(card1);
panel.add(card2);

//now we want to get the String identifier of the top card:
JPanel card = null;
for (Component comp : panel.getComponents()) {
    if (comp.isVisible() == true) {
        card = (JPanel) comp;
    }
}
System.out.println(card.getName());

Cimino

The notion of searching the top level JPanel for visible components (hopefully only one is visible) is the important part. Whether the panels have names or not is secondary. Once I have a handle to the current card panel, I can do all sorts of useful things – Supplicate