e899. setting an accessory component in a jfilechooser dialog.txt

这里面包含了一百多个JAVA源文件

The accessory is an optional component that can be added to a file chooser dialog to show a preview image of the selected file. By default, a file chooser dialog does not have an accessory installed. This example demonstrates how to install an accessory component. 
    JFileChooser chooser = new JFileChooser();
    
    // Create and set the accessory
    chooser.setAccessory(new MyAccessory(chooser));
    
    // Show the dialog; wait until dialog is closed
    chooser.showOpenDialog(frame);
    
    public class MyAccessory extends JComponent implements PropertyChangeListener {
        public MyAccessory(JFileChooser chooser) {
            // Listen for changes to the selected file
            chooser.addPropertyChangeListener(this);
    
            // Set a preferred size
            setPreferredSize(new Dimension(50, 50));
        }
    
        // This listener listens for changes to the selected file
        public void propertyChange(PropertyChangeEvent evt) {
            if (JFileChooser.SELECTED_FILE_CHANGED_PROPERTY.equals(
                    evt.getPropertyName())) {
                JFileChooser chooser = (JFileChooser)evt.getSource();
    
                // Get the new selected file
                File newFile = (File)evt.getNewValue();
    
                // Prepare the preview data based on the new selected file
    
                // Repaint this component
                repaint();
            }
        }
    
        public void paint(Graphics g) {
            // Paint a preview of the selected file
        }
    }

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