JavaFX How to get stage from controller during initialization

Question

I want to handle stage events  i e  hiding  from my controller class  So all I have to do is to add a listener via    Stage myPane getScene   getWindow    setOn whatIwant          but the problem is that initialization starts right after  Parent root   FXMLLoader load getClass   getResource  MyGui fxml       and before   Scene scene   new Scene root   stage setScene scene     thus  getScene   returns null   The only workaround I found by myself is to add a listener to myPane sceneProperty    and when it becomes not null I get scene  add to it s  windowProperty   my  goddamn  listener handling which I finally retrieve stage  And it all ends with setting desired listeners to stage events  I think there are too many listeners  Is it the only way to solve my problem

User · Accepted Answer

You can get the instance of the controller from the FXMLLoader after initialization via getController(), but you need to instantiate an FXMLLoader instead of using the static methods then.

I'd pass the stage after calling load() directly to the controller afterwards:

FXMLLoader loader = new FXMLLoader(getClass().getResource("MyGui.fxml"));
Parent root = (Parent)loader.load();
MyController controller = (MyController)loader.getController();
controller.setStageAndSetupListeners(stage); // or what you want to do

User · Answer

Platform runLater works to prevent execution until initialization is complete   In this case  i want to refresh a list view every time I resize the window width     Platform runLater    - gt          Stage  listView getScene   getWindow    widthProperty   addListener  obs  oldVal  newVal  - gt            listView refresh                  in your case  Platform runLater   - gt         Stage myPane getScene   getWindow    setOn whatIwant

User · Answer

I know it s not the answer you want  but IMO the proposed solutions are not good  and your own way is   Why  Because they depend on the application state  In JavaFX  a control  a scene and a stage do not depend on each other  This means a control can live without being added to a scene and a scene can exist without being attached to a stage  And then  at a time instant t1  control can get attached to a scene and at instant t2  that scene can be added to a stage  and that explains why they are observable properties of each other    So the approach that suggests getting the controller reference and invoking a method  passing the stage to it adds a state to your application  This means you need to invoke that method at the right moment  just after the stage is created  In other words  you need to follow an order now   1- Create the stage  2- Pass this created stage to the controller via a method   You cannot  or should not  change this order in this approach  So you lost statelessness  And in software  generally  state is evil  Ideally  methods should not require any call order   So what is the right solution  There are two alternatives   1- Your approach  in the controller listening properties to get the stage  I think this is the right approach  Like this   pane sceneProperty   addListener  observableScene  oldScene  newScene  - gt        if  oldScene    null  amp  amp  newScene    null               scene is set for the first time  Now its the time to listen stage changes          newScene windowProperty   addListener  observableWindow  oldWindow  newWindow  - gt                if  oldWindow    null  amp  amp  newWindow    null                       stage is set  now is the right time to do whatever we need to the stage in the controller                    Stage  newWindow  maximizedProperty   addListener  a  b  c  - gt                        if  c                            System out println  I am maximized                                                                                     2- You do what you need to do where you create the Stage  and that s not what you want    Stage stage   new Stage    stage maximizedProperty   addListener  a  b  c  - gt                if  c                    System out println  I am maximized                               stage setScene someScene

User · Answer

The simplest way to get stage object in controller is    Add an extra method in own created controller class like  it will be a setter method to set the stage in controller class    private Stage myStage  public void setStage Stage stage         myStage   stage     Get controller in start method and set stage  FXMLLoader loader   new FXMLLoader getClass   getResource  MyFXML fxml     OwnController controller   loader getController    controller setStage this stage    Now you can access the stage in controller

User · Answer

All you need is to give the AnchorPane an ID  and then you can get the Stage from that    FXML private AnchorPane ap  Stage stage    Stage  ap getScene   getWindow      From here  you can add in the Listener that you need   Edit  As stated by EarthMind below  it doesn t have to be the AnchorPane element  it can be any element that you ve defined

User · Answer

Assign fx id or declare variable to of any node  anchorpane  button  etc  Then add event handler to it and within that event handler insert the given code below   Stage stage    Stage   Node   EventObject  eventVariable  getSource    getScene   getWindow      Hope  this works for you

User · Answer

You can get with node getScene  if you don t call from Platform runLater  the result is a null value   example null value   node getScene      example no null value   Platform runLater    - gt        node getScene   addEventFilter KeyEvent KEY PRESSED  event - gt                     your event

[javafx] JavaFX: How to get stage from controller during initialization?

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