Adding Buttons on Custom JPanel

Question

i have the following problem. i want to paint something on a custom jpanel and then set custom buttons on a absolute positions. these buttons should listen on clicking and then provide their position. but everything i tried is not working. the buttons are not displaying when i use add();

    public class IslePanel extends JPanel {

    private static final long serialVersionUID = 1L;

    private Color backgroundColor = new Color(90, 74, 66);
    private Color strokeColor = new Color(254, 254, 254);
    private Color lightGrayColor = new Color(220, 220, 220);

    /**
     * Constructor of the GameView
     * 
     * @param game
     * @param controller
     */
    public IslePanel() {
        setBackground(backgroundColor);
        SiteButton sb = new SiteButton();
        sb.setXPos(100);
        sb.setYPos(100);
        sb.setSiteRadius(20);
        add(sb);
        //example: i plan to draw a circle formed button on absolute Position (100,100) radius 20
    }


    /**
     * paintComponent-method for ALL drawing functions
     * 
     * @param Graphics
     *            g
     * 
     **/
    public void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2 = (Graphics2D) g;
            g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
            try {
                drawTile(g, tile);
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
    }

sitebutton superclass:

public abstract class CustomButton extends JPanel implements MouseListener {

    private Vector listeners = null;

    boolean hit = false;

    public CustomButton(String title) {
        super();
        this.title = title;
        listeners = new Vector();
        addMouseListener(this);
    }

//  public Dimension getPreferredSize() {
//      return new Dimension(120, 80);
//  }


    public void mousePressed(MouseEvent e) {
    }

    public void mouseReleased(MouseEvent e) {

    }

    public void mouseClicked(MouseEvent e) {
        fireEvent(new ActionEvent(this, 0, title));
        System.out.println("bauen");        
    }

    public void mouseEntered(MouseEvent e) {
    }

    public void mouseExited(MouseEvent e) {
    }

    public void addActionListener(ActionListener listener) {
        listeners.addElement(listener);
    }

    public void removeActionListener(ActionListener listener) {
        listeners.removeElement(listener);
    }

    private void fireEvent(ActionEvent event) {
        for (int i = 0; i < listeners.size(); i++) {
            ActionListener listener = (ActionListener) listeners.elementAt(i);
            listener.actionPerformed(event);
        }
        ;
    }
}

the button class:

public class SiteButton extends CustomButton {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    private double xpos,ypos;

    private Site site;

    private int siteRadius;

    @Override
    public void paintComponent(Graphics g) {
//      super.paintComponent(g);
        Graphics2D g2D = (Graphics2D) g;

        g2D.setColor(Color.BLACK);
        g2D.fillOval((int)xpos-siteRadius/2, (int)ypos-siteRadius/2, siteRadius, siteRadius);       
    }

    @Override
    public void mouseClicked(MouseEvent e) {
        System.out.println(""+xpos + ypos);     
    }

Answer 1

You might be better off using an ActionListener than a MouseListener. Not only would it save you a few lines, but it always seems to work for me. mouseClicked is only invoked when the user clicks their LMB over the button (obviously resulting in the button being pressed, but it isn't as direct). actionPerformed is invoked whenever the user performs an ActionEvent on the button (i.e. directly clicking the button).

Not to mention, buttons, by default, fire ActionEvents

The MouseListener is intended to determine if you're holding down the mouse button, if you've released the mouse button, or if you've just "clicked" (or double clicked) the mouse button - regardless of where the mouse is in the listening component.

Also, if you were to click your LMB over the button, but then drag your mouse before you were to release the LMB, the button would still execute.

As to your problem, have you tried using revalidate();?

revalidate() invalidates every component, then validates them.

The problem, is that when you call JPanel.add(button); you immediately invalidate the Container, or in your case, the JPanel. To fix this, you can either call revalidate(); or JPanel.validate();. The difference is that revalidate(), like I said previously, enacts on every component versus validate() which enacts on just one component.