JAVAFX add dynamic element in a FXML Gridpane - javafx

Question

In my FXML I created a gridpane. Now I want to add dynamic element (Like button, textfield)
by java code (not by FXML), while I am trying to do so, I am getting error. Please Help.
my FXML:
<AnchorPane fx:controller="tableview.TableViewSample" id="AnchorPane" maxHeight="- Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns:fx="http://javafx.com/fxml">
<children>
<GridPane fx:id="greadpane" layoutX="0.0" layoutY="0.0" prefHeight="400.0" prefWidth="600.0">
<columnConstraints>
<ColumnConstraints fx:id="col0" hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints fx:id="row0" minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
</rowConstraints>
</GridPane>
</children>
</AnchorPane>
My Java Code:
public class TableViewSample extends Application {
#FXML private GridPane greadpane;
public static void main(String[] args) {
launch(args);
}
#Override
public void start(Stage stage) throws IOException {
Pane myPane = (Pane)FXMLLoader.load(getClass().getResource
("tabviewexamlpe.fxml"));
Scene scene = new Scene(myPane);
stage.setTitle("Table View ");
stage.setWidth(450);
stage.setHeight(500);
stage.setScene(scene);
final Label label = new Label("Address Book");
label.setFont(new Font("Arial", 20));
greadpane.add(label, 0, 0);
stage.show();
}
}

Answer 1

You get a null pointer cause you try to do operation before stage.show() so fxml are not yet initialized. don't do dirty things and put your greadPane.add on a separate controller
public class Controller implements Initializable {
#FXML
private GridPane greadpane;
#Override
public void initialize(URL url, ResourceBundle resourceBundle) {
final Label label = new Label("Address Book");
label.setFont(new Font("Arial", 20));
greadpane.add(label, 0, 0);
}
}
and assign your fxml to this controler. and it's will be ok

Answer 2

I ran into the same problem and used Agonist_ advice, however instead of separating the gridPane into a new controller i just created a thread that runs 10ms later to execute the code which is waiting for stage.show().
public GameController(Game game) {
game.addObserver(this);
new Thread() {
#Override
public void run() {
try {
Thread.sleep(10);
Platform.runLater(() -> {
game.startBeginnerRound();
});
} catch (InterruptedException ex) {
Logger.getLogger(GameController.class.getName()).log(Level.SEVERE, null, ex);
}
}
}.start();
}
In this example the gridPane is updated when the observable notifies it, in this case when game.startBeginnerRound() is executed.