mxGraph JButton inside a Custom Swing Canvas?

Following the example in CustomCanvas.java
I've managed to paint a JButton inside a custom Swing canvas for an mxCell with this code

        public void drawVertex(mxCellState state, String label)
        {
           
            Object value = ((mxCell) state.getCell()).getValue();
            Pattern p = (Pattern)value;
            System.out.println(p.length);
            MyPanel comp = new MyPanel();
            
            rendererPane.paintComponent(g, comp, graphComponent,
                    (int) (state.getX() + translate.getX()),
                    (int) (state.getY() + translate.getY()),
                    (int) state.getWidth(), (int) state.getHeight(), true);
            
            g.setColor(Color.GREEN);
            for (int i = 0; i < p.length; i++) {
                JButton b = new JButton("");
                b.addActionListener(new ActionListener() {
                    public void actionPerformed(ActionEvent e) {
                       System.out.println("click,click");
                    }          
                 });
                rendererPane.paintComponent(g, b, graphComponent,
                    (int) (state.getX() + translate.getX()+i*state.getWidth()/p.length),
                    (int) (state.getY() + translate.getY()),
                    (int) state.getWidth()/p.length, (int) state.getHeight(), true);
            }
        }

the button gets painted but it isn't working and if I click it nothing happens

If you want the component to be interactive, you have to add it to container (which itself is added to another container, eventually reaching a JFrame). What you have now just paints it into a cell.

Theoretically you could bend-over-backwards to intercept clicks to the cell and forward them to the JButton, but that's probably not a sustainable approach.