Question

I am using a JColorchooser at various places in an application. There can be multiple instances of the panel that can invoke a JColorChooser.
The “Swatches” panel in the chooser has an area of “recent” colors, which only persists within each instance of JColorChooser. I would like to (a) have the same “recent” colors in all my choosers in my application, and (b) to save the colors to disk so that these colors survive close and restart of the application.
(At least (a) could be solved by using the same single chooser instance all over the whole app, but that apears cumbersome because I would need to be very careful with attached changelisteners, and adding/removing the chooser panel to/from various dialogs.)

I did not find any method that lets me set (restore) these “recent” colors in the chooser panel. So to me, it appears that the only ways of achieving this would be:

• serialize and save / restore the whole chooser (chooser panel?)
  or
• create my own chooser panel from scratch

Is this correct, or am I missing something?

BTW: I would also like to detect a double click in the chooser, but it seems hard to find the right place to attach my mouse listener to. Do I really need to dig into the internal structure of the chooser panel to do this? (No, it does not work to detect a second click on the same color, because the change listener only fires if a different color is clicked.)

Answer 1

As you noticed, there is no public api to access the recent colors in the DefaultSwatchChooserPanel, even the panel itself isn’t accessible.

As you’ll need some logic/bean which holds and resets the recent colors anyway (plus the extended mouse interaction), rolling your own is the way to go. For some guidance, have a look at the implementation of the swatch panel (cough … c&p what you need and modify what you don’t). Basically, something like

// a bean that keeps track of the colors
public static class ColorTracker extends AbstractBean {

    private List<Color> colors = new ArrayList<>();

    public void addColor(Color color) {
        List<Color> old = getColors();
        colors.add(0, color);
        firePropertyChange("colors", old, getColors());
    }

    public void setColors(List<Color> colors) {
        List<Color> old = getColors();
        this.colors = new ArrayList<>(colors);
        firePropertyChange("colors", old, getColors());
    }

    public List<Color> getColors() {
        return new ArrayList<>(colors);
    }
}

// a custom SwatchChooserPanel which takes and listens to the tracker changes
public class MySwatchChooserPanel ... {

   ColorTracker tracker;

   public void setColorTracker(....) {
       // uninstall old tracker 
       ....
       // install new tracker
       this.tracker = tracker;
       if (tracker != null) 
           tracker.addPropertyChangeListener(.... );
       updateRecentSwatchPanel()
   }

   /** 
    * A method updating the recent colors in the swatchPanel
    * This is called whenever necessary, specifically after building the panel,
    * on changes of the tracker, from the mouseListener
    */
   protected void updateRecentSwatchPanel() {
       if (recentSwatchPanel == null) return;
       recentSwatchPanel.setMostRecentColors(tracker != null ? tracker.getColors() : null);
   }

// the mouseListener which updates the tracker and triggers the doubleClickAction
// if available
class MainSwatchListener extends MouseAdapter implements Serializable {
    @Override
    public void mousePressed(MouseEvent e) {
        if (!isEnabled())
            return;
        if (e.getClickCount() == 2) {
            handleDoubleClick(e);
            return;
        }

        Color color = swatchPanel.getColorForLocation(e.getX(), e.getY());
        setSelectedColor(color);
        if (tracker != null) {
            tracker.addColor(color);
        } else {
            recentSwatchPanel.setMostRecentColor(color);
        }
    }

    /**
     * @param e
     */
    private void handleDoubleClick(MouseEvent e) {
        if (action != null) {
            action.actionPerformed(null);
        }
    }
}


} 

// client code can install the custom panel on a JFileChooser, passing in a tracker
private JColorChooser createChooser(ColorTracker tracker) {
    JColorChooser chooser = new JColorChooser();
    List<AbstractColorChooserPanel> choosers = 
            new ArrayList<>(Arrays.asList(chooser.getChooserPanels()));
    choosers.remove(0);
    MySwatchChooserPanel swatch = new MySwatchChooserPanel();
    swatch.setColorTracker(tracker);
    swatch.setAction(doubleClickAction);
    choosers.add(0, swatch);
    chooser.setChooserPanels(choosers.toArray(new AbstractColorChooserPanel[0]));
    return chooser;
}

As to doubleClick handling: enhance the swatchChooser to take an action and invoke that action from the mouseListener as appropriate.