title: How to run a function after Stage.show()?
body: <p>I'm struggling with a problem where one chunk of code runs before it's initialized.</p>
  <pre><code>@FXML
  public void Start(int pesel) throws IOException {
      klientPesel = pesel;
      root = FXMLLoader.load(getClass().getClassLoader().getResource(&quot;klientScene.fxml&quot;));
      Main.mainStage.setTitle(&quot;Agencja Ubezpieczniowa - Agent&quot;);
      Scene scene = new Scene(root,800,600);
      Main.mainStage.setScene(scene);
      Main.mainStage.show();
      obtainKlient();
      setKlientLabels();
  }
  </code></pre>
  <p>The problem is that I have a variable <code>@FXML private VBox KlientInfoVBOX;</code> and it's not initialized before <code>setKlientLabels()</code> runs. How do I make sure that <code>setKlientLabels()</code> will run after <code>Main.mainStage.show();</code>?</p>
  <p>Maybe stacktrace will help to resolve the problem</p>
  <pre><code>Exception in thread &quot;JavaFX Application Thread&quot; java.lang.NullPointerException
      at app.KlientSearchController.setKlientLabels(KlientSearchController.java:69)
      at app.KlientSearchController.Start(KlientSearchController.java:51)
      at app.UserSceneController.StartKlientSearch(UserSceneController.java:87)
      at app.UserSceneController.lambda$wyszukajKlienta$0(UserSceneController.java:70)
      at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
      at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
      at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
      at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
      at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
      at javafx.event.Event.fireEvent(Event.java:198)
      at javafx.scene.Node.fireEvent(Node.java:8411)
      at javafx.scene.control.Button.fire(Button.java:185)
      at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
      at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
      at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
      at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
      at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
      at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
      at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
      at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
      at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
      at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
      at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
      at javafx.event.Event.fireEvent(Event.java:198)
      at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
      at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
      at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
      at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
      at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:352)
      at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:275)
      at java.security.AccessController.doPrivileged(Native Method)
      at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:388)
      at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
      at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:387)
      at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
      at com.sun.glass.ui.View.notifyMouse(View.java:937)
      at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
      at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
      at java.lang.Thread.run(Thread.java:745)
  </code></pre>
  <p>If I remove <code>setKlientLabels()</code> from the code to run there are no exceptions, everything runs smoothly.</p>