JLabel containing an ImageIcon won't repaint

Question

I'm writing an application that creates a deck of cards in a random order and when a button is pressed moves the top card to the bottom and shows the new top card. (It's to simulate a Planechase deck to those familiar with Magic: the Gathering.) When the button is pressed it is properly cycling through the image files, but when I assign an image to a JLabel with an ImageIcon I can't get the JLabel to refresh with the new image. Here's the code I'm using to refresh

    nextCardButton.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            planechase.topCardIncrement();
            createCardToDisplay();
        }
    });

planechase is an instance of a class CardDeck which stores the randomized deck and has several methods to shuffle, change cards, etc. topCardIncrement() changes the top card to the next in the list.

    private void createCardToDisplay()
    {
    cardToDisplay = new JLabel(new ImageIcon(planechase.getFolderName() + "\\" + planechase.displayTopCard()));
    }

createCardToDisplay assigns cardToDisplay to an image derived from the folder name of the images and the current file. cardToDisplay is placed within JPanel contentPanel which is placed within JFrame frame. I can't figure out the proper way to repaint/revalidate (I'm not quite clear on what the difference is) my GUI to reflect the updated image. I've confirmed via System.out.println calls that

    planechase.getFolderName() + "\\" + planechase.displayTopCard()

is updating as it should, so I assume that the JLabel is being reassigned properly. What is the proper way to redraw this so that it reflects the new ImageIcon?

Where are the images stored relative to the class? Have you tried loading the images with ImageIO.read which will throw an IOException when something goes wrong... — MadProgrammer
In your code example, you are creating a new instance of cardToDisplay, but not adding to anything...this could be cause of your problem, but there is no context by which it would be possible to be sure. Consider providing a runnable example which demonstrates your problem. This will result in less confusion and better responses — MadProgrammer
"What is the proper way to redraw this so that it reflects the new ImageIcon?" cardToDisplay.setIcon(new ImageIcon(planechase.getFolderName() + "\\" + planechase.displayTopCard())); ... but as per my previous comment, there is no context to be sure that this is the correct thing to do in you case... — MadProgrammer
Mad, the images are stored MagicMultiplayerApplication\planes\"...".jpg relative to MagicMultiplayerApplication\src\"...".java The first image displays itself, and the paths for subsequent images are correct, it's just a matter of properly repainting the JPanel. And Jaco, I have tried repainting the JLabel's container. Does the label update if I just call createCardToDisplay again? or do I have to set the previous cardToDisplay to some null value? — SnappleCaptain

MadProgrammer MadProgrammer · Accepted Answer · 2014-08-06T06:54:31

The code is ambiguous...

The first thing that jumps out at me is...

private void createCardToDisplay()
{
    cardToDisplay = new JLabel(new ImageIcon(planechase.getFolderName() + "\\" + planechase.displayTopCard()));
}

This is creating a new instance of cardToDisplay, but is it been added anywhere? Is the previous instance been removed? There's no context to be certain.

Normally, when you want to change the icon of a JLabel, you would simply call setIcon on the instance of the JLabel...

cardToDisplay.setIcon(new ImageIcon(planechase.getFolderName() + "\\" + planechase.displayTopCard()));

Because this is a bound field, it will trigger a repaint request automatically.

JLabel containing an ImageIcon won't repaint

1 Answers