刷新JLabel-Java

Question

I have some problems with JLabels and Frames..

I have the following code:

 list.addListSelectionListener(
            new ListSelectionListener() {

                @Override
                public void valueChanged(ListSelectionEvent e) {
                    //System.out.println(e.getFirstIndex());


                    String selectedFile = list.getSelectedValue().toString();
                    System.out.println("Selected file " + selectedFile);
                    JLabel label;
                    ImageIcon icon = new ImageIcon("C:\\Users\\danie\\Pictures\\" + selectedFile);
                    // frame.setSize(1047, 680);
                     label = new JLabel(icon);
                     //label.setSize(100,100);
                     frame.getContentPane().add(label, BorderLayout.CENTER);
                     frame.revalidate();
                     frame.repaint();

                }

    });

I want to refresh the label in the center of the borderlayout if a item in a JList is selected. But with this code, the old image is futher displayed and the new image is only drawed behind the existing image.

Could anyone help me? :)

Answer 1

First you are creating a new JLabel instance instead of working on the existing one. What you actually want to do is:

labe.setIcon(icon);

This will automatically refresh the element.

Answer 2

Suggestions:

1. Don't create a new JLabel, give it an ImageIcon and expect the existing JLabel to change. The two JLabels, the original one and the one created here, are two completely different objects, and changing the state of one (the icon it's displaying) will not magically change the state of the other.
2. Do make sure that the original JLabel has an instance variable in the class (not in your listener class), a field, refer to it, and then in your listener code, change the icon displayed in that JLabel by calling its setIcon(...) method
3. No need to call revalidate() or repaint() here as this should be done if you change components held within a container, such as if you removed the original JLabel from the JFrame's contentPane and swapped in a new one. Note that I do not recommend that you do this as it is over-complicating what should be a simple thing -- swapping icons.
4. To simplify things, I suggest that you read all your images in at program startup, create ImageIcons at that time, and then put them into an array or collection (such as an ArrayList<Icon> or a HashMap<String, Icon> ), and then in your listener code, extract the correct icon, and put it into the existing JLabel.

Answer 3

You are not using the same JLabel it seems. You should alter the label you already have, not create a new one.