netbeans plugin run method but not when action event fire

i started netbeans plugin development with this basic tutorial . and i modyfied it to get the text of current edited file.

so i created a action class which extends ActionListener .so when i click the icon of my plugin from toolbar it open dialog and show content.but it repeats .when i close another one open then another dialog so on..

i think this is because i add property each time listener when i click the button .so how can i fix this ..

this is the code i used

public final class SomeAction implements ActionListener {

    @Override
    public void actionPerformed(ActionEvent e) {
        PropertyChangeListener l = new PropertyChangeListener() {
            @Override
            public void propertyChange(PropertyChangeEvent evt) {
                JTextComponent jtc = EditorRegistry.lastFocusedComponent();
                if (jtc != null) {
                    Document d = jtc.getDocument();
                    int msgType = NotifyDescriptor.INFORMATION_MESSAGE;
                    NotifyDescriptor df;
                    try {
                        df = new NotifyDescriptor.Message(d.getText(0, d.getLength() - 1), msgType);
                        DialogDisplayer.getDefault().notify(df);
                    } catch (BadLocationException ex) {
                        Exceptions.printStackTrace(ex);
                    }

                }
            }
        };

        EditorRegistry.addPropertyChangeListener(l);  // i guess here is the problem but i couldn't able to find where should i put this line 

    }

via Chebli Mohamed