Updating swing components correctly?

Question

I'm new to swing, any help appreciated.

In this piece of code I'm turning a card over face up, if it turns out that they don't match I want them to turn back face down again.

At the moment what is happening: 1. when clicked the first card turns over 2. when a second card is clicked either of two things happen (a) if they are the same they both stay up which is what I want (b) if they are not the same I never see the 2nd card at all as it immediately re-displays the back of the card (and the back of the previous card also as defined in my method).

I thought putting in the sleep timer might keep the 2nd card displayed for a period of time before turning back over but it does not.

I attempted to use contentPane.revalidate(); & contentPane.repaint(); but it doesn't change anything.

I have put in some console outputs:

Console output:
Card: 0 set
Card: 6 set
Sleeping now
Card: 6 unset
Card: 0 unset

Above is the resulting console output when clicking two card which do not match

@Override
public void actionPerformed(ActionEvent e) 
{
    String buttonPressed = e.getActionCommand();
    int pos = Integer.valueOf(buttonPressed);
    action = Control.model.ReceiveCardsTurned(pos);

    keypadArray[pos].setIcon(myIcons[pos]);     
    System.out.println("Card: "+pos+" set");
    currentTime.setText("" + Control.model.time);
    currentScore.setText("" + Control.model.score);

    //contentPane.revalidate();
    //contentPane.repaint();        

    if(Control.model.twoCardsTurned == false)
    {
        if (action == "unturn") 
        {
            System.out.println("Sleeping now");

            try 
            {
                Thread.sleep(1000);
            }

            catch (InterruptedException e1) 
            {
                e1.printStackTrace();
            }

            keypadArray[pos].setIcon(back);
            keypadArray[Control.model.lastCard].setIcon(back);
            System.out.println("Card: "+pos+" unset");
            System.out.println("Card: "+Control.model.lastCard+" unset");
        }
    }
}

Answer 1

You can't sleep in the event dispatch thread, because your GUI will freeze. You have to use Swing Timer. For background tasks you'll probably have to worry about in the future, take a look at SwingWorker.