swing - Java: Add panel to existing panel after runtime -

im trying add new card existing jpanel(cardlayout) click of jbutton , goto new card null exception new card not registering.

ive tried searching google cant find , example , ive tried make 'save' layout using

.validate(); .refresh(); .repaint(); 

but nothing works, possible dynamically? , if know of example?

code below, jpanelsliding1.nextslidpanel moves selected jpanel in cardlayout. new panel created here causing null error panel not found. thanks:)

/* * change template, choose tools | templates * , open template in editor. */ package partnerships;  import components.colorscheme; import components.utilities; import java.awt.borderlayout; import java.awt.color; import java.awt.gridlayout; import java.beans.propertychangeevent; import java.beans.propertychangelistener; import java.beans.propertychangesupport; import javax.swing.jbutton; import javax.swing.jframe; import javax.swing.jpanel;  public class jslidingpanel extends javax.swing.jpanel implements propertychangelistener {      public propertychangesupport pcs = new propertychangesupport(this);     private colorscheme scheme;      public jslidingpanel() {         initcomponents();         pcs.addpropertychangelistener(this);         scheme = new colorscheme();         object[][] object = {             {pcs, "offered", "bt details", scheme.green()},             {pcs, "sold", "bt details", scheme.pink()},             {pcs, "other", "bt details", scheme.purple()}         };          jpanelsliding1.add(makepanels(object));     }      private void setupgui() {     }      private jpanel makepanels(object[][] objects) {         jpanel panel = new jpanel();         panel.setlayout(new gridlayout(0, objects.length));         (object[] properties : objects) {             panel.add(new objectpanel((propertychangesupport) properties[0], properties[1].tostring(), properties[2].tostring(), (color) properties[3]));         }         return panel;     }      private void newpanel(string str) {         jpanel panel = new jpanel();         panel.setlayout(new borderlayout());         panel.add(new jbutton());         jpanelsliding1.add(panel);          jpanelsliding1.refresh();         jpanelsliding1.validate();         jpanelsliding1.repaint();          validate();         repaint();         utilities.gettopframe().pack();         jpanelsliding1.nextslidpanel(10, panel);         jpanelsliding1.refresh();     }      @override     public void propertychange(propertychangeevent evt) {         if (this.isvisible() == true) { //            makepanels();             newpanel(evt.getpropertyname());         }     }      public static void main(string args[]) {         java.awt.eventqueue.invokelater(new runnable() {             @override             public void run() {                 jframe frame = new jframe();                 jpanel panel = new jpanel();                 jslidingpanel app = new jslidingpanel();                  panel.add(app);                 frame.add(panel);                 frame.setdefaultcloseoperation(javax.swing.windowconstants.dispose_on_close);                 frame.setvisible(true);                 frame.pack();             }         });     }      /**      * method called within constructor initialize form.      * warning: not modify code. content of method      * regenerated form editor.      */     @suppresswarnings("unchecked")     // <editor-fold defaultstate="collapsed" desc="generated code">                              private void initcomponents() {          jpanelsliding1 = new apps.jpanelsliding();          setpreferredsize(new java.awt.dimension(900, 600));         setlayout(new java.awt.borderlayout());          jpanelsliding1.setlayout(new java.awt.cardlayout());         add(jpanelsliding1, java.awt.borderlayout.center);     }// </editor-fold>                            // variables declaration - not modify                         private apps.jpanelsliding jpanelsliding1;     // end of variables declaration                   } 

if dealing changing card of window on event, following may help.

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