CardLayout get the selected card's name

问题:

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

回答1:

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

回答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());