title: javaFX-scene builder button event doesn't work
body: <p>I'm trying from yesterday javaFX and scene builder in a very simple application to get button click to work, but everything I tried(by following some tutorials or related answers here) it doesn't work.
  I created a new javaFX project and these are the files created with my editings:</p>
  
  <p><strong>Main.java:</strong></p>
  
  <pre><code> import javafx.application.Application;
   import javafx.stage.Stage;
   import javafx.scene.Scene;
   import javafx.scene.layout.Pane;
   import javafx.fxml.FXMLLoader;
  
   public class Main extends Application {
  
       @Override
       public void start(Stage primaryStage) {
           try {
              FXMLLoader loader = new 
          FXMLLoader(getClass().getResource("sample.fxml"));
          loader.setController(new SampleController());
          Pane root = loader.load();
              Scene scene = new Scene(root,400,400);
              scene.getStylesheets().add(getClass().getResource
              ("application.css").toExternalForm());
              primaryStage.setScene(scene);
              primaryStage.show();
           } catch(Exception e) {
              e.printStackTrace();
           }
      }
  
      public static void main(String[] args) {
          launch(args);
      }
  }
  </code></pre>
  
  <p><strong>SampleControler.java:</strong></p>
  
  <pre><code>package application;
  
  import java.net.URL;
  import java.util.ResourceBundle;
  import javafx.event.ActionEvent;
  import javafx.fxml.FXML;
  import javafx.fxml.Initializable;
  import javafx.scene.control.Button;
  import javafx.scene.control.Label;
  
  public class SampleController implements Initializable{
  
      @FXML
      Button bOk;
      @FXML
      Label lbTest;
  
      private void handleButtonAction(ActionEvent event) {
           // Button was clicked, do something...
           lbTest.setText("Button Action\n");
      }
  
      @Override
      public void initialize(URL location, ResourceBundle resources) {
          // TODO Auto-generated method stub
          bOk.setOnAction(this::handleButtonAction);
      }
  
  }
  </code></pre>
  
  <p><strong>sample.fxml:</strong></p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  
  &lt;?import javafx.scene.control.Button?&gt;
  &lt;?import javafx.scene.control.Label?&gt;
  &lt;?import javafx.scene.layout.Pane?&gt;
  
  
  &lt;Pane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" 
      minWidth="-Infinity" prefHeight="220.0" prefWidth="484.0" 
      xmlns="http://javafx.com/javafx/8.0.111" 
      xmlns:fx="http://javafx.com/fxml/1"&gt;
     &lt;children&gt;
        &lt;Button id="bOk" layoutX="214.0" layoutY="152.0" 
      mnemonicParsing="false" text="Button" /&gt;
        &lt;Label id="lbTest" layoutX="214.0" layoutY="57.0" prefHeight="25.0" 
      prefWidth="138.0" text="Label" /&gt;
     &lt;/children&gt;
  &lt;/Pane&gt;
  </code></pre>
  
  <p>The above doesn't give any error, but when button clicked it doesn't do anything(supposed to change Label' s text).
  I tried to set onAction on fxml file but this always gives error(cannot resolve onAction), no matter what I put there or if I do it from scene builder or by manually edit the fxml file(I have created the method and wrote it correct in onAction). 
  What I'm doing wrong?</p>
  
  <p>The error I'm getting now:</p>
  
  <pre><code>    javafx.fxml.LoadException: 
  /home/workspace/testapp/bin/application/sample.fxml
  
      at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
      at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2579)
      at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
      at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2409)
      at application.Main.start(Main.java:16)
      at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
      at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
      at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
      at java.security.AccessController.doPrivileged(Native Method)
      at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
      at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
      at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
      at com.sun.glass.ui.gtk.GtkApplication.lambda$null$49(GtkApplication.java:139)
      at java.lang.Thread.run(Thread.java:745)
  Caused by: java.lang.NullPointerException
      at application.SampleController.initialize(SampleController.java:27)
      at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2548)
  </code></pre>
  
  <p><em>After I used fx:id instead of id for button and label the button worked as expected and the above errors gone.</em></p>