im trying to learn about JavaFX and bumped into NullPointerException for Controller. Meaning everytime i use the instance of controller, eclipse show the Exception. I have read severals similar questions but non of this solved my case.
Here is the code snippet that caused the Exception
public GuiController (Stage a) throws IOException  {
    this.priStage = a;
    FXMLLoader fxLoader = new FXMLLoader(getClass().getClassLoader().getResource("View/OverviewWindow.fxml"));  
    overviewController = fxLoader.getController();
    overviewController.getRefreshButton().setText("Oh no"); **// When i remove this line everything works fine!**
    Parent root = fxLoader.load();
    priStage.setScene(new Scene(root));
    priStage.show();
}
Here is my Controller class, basicly nothing :
public class OverviewWindow implements Initializable {
    @FXML TextField searchTextField;
    @FXML
    private Button standardButton;
    @FXML
    private Button refreshButton;
    @FXML
    private RadioButton mitArchivRadioButton;
    @FXML
    private RadioButton nurArchivButton;
    @Override
    public void initialize(URL a, ResourceBundle b) {
    }
    public OverviewWindow() {
    }
}
my stack trace
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NullPointerException
at Controller.GuiController.<init>(GuiController.java:31)
at Controller.Controller.init(Controller.java:33)
at main.start(main.java:24)
Can someone help me ? I read about this problem for days and tried manyway to set the controller right but couldnt do it. Thanks.
 
    