java - Javafx: Create new stage in application -

i need some quite simple code (i think) work. have jframe starts application play video (twice, differenct video each time) , shows couple of jbuttons answer questions on videos. problem first video show, can't create new stage. maybe can me. code in panel:

public void ausführen(int i, int antwort){      switch (antwort) {         case 0:             //question or video                                switch (i) {                 case 0:                     //film1                     mp = new mediapanel(); //this application                     mp.run();                     setvisible(false); //this timer waits video finish                     task = new java.util.timertask(){                     @override                     public void run(){                         setvisible(true);                                                     ausführen(1,0);                                                  }                     };                     t = new java.util.timer();                     t.schedule(task, 7000);                                                                               break;                 case 1:       //film2                                      mp.restart(new stage(),"other video");                     setvisible(false);                                             task = new java.util.timertask(){                     @override                     public void run(){                         setvisible(true);                                                     ausführen(2,0);                                                                                    dispose();                                                 }                     };                     t = new java.util.timer();                     t.schedule(task, 7000); //next case opens jpanel jbuttons questions (works) 

this code in mediapanel (the application):

public class mediapanel extends application implements runnable {      private string film = "video1";      public void setfilm(string f){         film = f;     }             @override     public void run(){         launch();     }         public void start( stage stage ) throws exception     {         group root = new group();         stage.settitle("movieplayer");         media media = new media("video1");         mediaplayer player = new mediaplayer(media);         mediaview view = new mediaview(player);          view.setpreserveratio(true);          root.getchildren().add(view);         scene scene = new scene(root, media.getwidth(), media.getheight(), color.black);          stage.setscene(scene);         stage.show();         stage.setfullscreen(false);          player.play();          java.util.timertask task = new java.util.timertask(){             @override             public void run(){                 system.out.print("still running"); //i wanted see if method called                 platform.exit();                 }                                                           };          java.util.timer t = new java.util.timer();         t.schedule(task, 5000);      }      public void restart( stage stage, string film ) //i created method avoid calling launch() twice     {         system.out.print("restart");         group root = new group();         stage.settitle("movieplayer");         media media = new media(film);         mediaplayer player = new mediaplayer(media);         mediaview view = new mediaview(player);           view.setpreserveratio(true);          root.getchildren().add(view);         scene scene = new scene(root, media.getwidth(), media.getheight(), color.black);          stage.setscene(scene);         stage.show();         stage.setfullscreen(true);          player.play();          java.util.timertask task = new java.util.timertask(){             @override             public void run(){                 platform.exit();                 }                                                           };          java.util.timer t = new java.util.timer();         t.schedule(task, 5000);                  }       } 

i error: "exception in thread "timer-2" java.lang.illegalstateexception: not on fx application thread; currentthread = timer-2". alternativley created new mediapanel in mediawindow, did'nt work either because 1 may not call launch() more once.

i know code isn't good, supposed easy gui/application.

i hope 1 of guys can me! thank in advance!