java - scrollbars adjust when zooming using Jxlayer and PBar extensions -

i tried use jxlayer , pbar extensions (using response of madprogrammer here) add zoom capability jpanel contained in jscrollpanel. zoom work fine when zoomed panel becomes larger containing jframe scrollbars doesn’t adjust , stay inactive. here code:

jframe frame = new jframe("testing"); frame.setdefaultcloseoperation(jframe.exit_on_close); frame.setlayout(new borderlayout()); jpanel toppanel = new jpanel(); integer[] zoomlist = {50, 75, 100, 125, 150, 200}; jcombobox<integer> zoombox = new jcombobox<>(zoomlist); zoombox.addactionlistener(new actionlistener() {                     @override                     public void actionperformed(actionevent ae) {                         int value = (int) zoombox.getselecteditem();                         double scale = value / 100d;                         transformmodel.setscale(scale);                     }                 }); toppanel.add(zoombox); panel centerpanel = new testpane(); jscrollpane scrollpane = new jscrollpane(synopticpanel); scrollpane.sethorizontalscrollbarpolicy(jscrollpane.horizontal_scrollbar_always); scrollpane.setverticalscrollbarpolicy(jscrollpane.vertical_scrollbar_always); scrollpane.getviewport().setopaque(false); scrollpane.setopaque(false); frame.add(toppanel, borderlayout.north); frame.add(synopticpanel); frame.pack(); frame.setlocationrelativeto(null); frame.setvisible(true); 

and in testpane class

public class testpane extends jpanel {      private jlayer<jcomponent> layer;     private jpanel content;      public testpane() {         content = new jpanel();         content.setlayout(null);         //adding components         transformmodel = new defaulttransformmodel();         transformmodel.setscaletopreferredsize(true);         layer = transformutils.createtransformjlayer(content, transformmodel, null);         setlayout(new borderlayout());         add(layer);     } 

thank help