How do i restart an application in JavaFx, built with FXML?

Question

Say I have a window, with a button. And everytime that button is pressed I want the current window to be disposed and a new one to be shown.

In Swing, that was easy, but I can't find the syntax for it in JavaFx? So in this case, with my example code, how do I do this?

public class Main extends Application {

    Parent root;
    Scene scene;

    @Override
    public void start(Stage primaryStage) throws Exception {
        root = FXMLLoader.load(getClass().getResource("FXMLDocument.fxml"));

        scene = new Scene(root);

        primaryStage.setScene(scene);

        primaryStage.sizeToScene();
        primaryStage.setResizable(false);

        primaryStage.show();


        root.setOnMouseClicked((MouseEvent mouseEvent) -> {
            if (mouseEvent.getButton().equals(MouseButton.PRIMARY)) {
                if (mouseEvent.getClickCount() == 2) {



                        Stage stage = new Stage();
                        stage.setScene(primaryStage.getScene());
                        stage.show();
                        primaryStage.close();


                }
            }
        });
    }


    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }
     }

Trying to create a new window: http://sv.tinypic.com/r/1jkq4w/8

FXML:

<?xml version="1.0" encoding="UTF-8"?>

<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.paint.*?>
<?import javafx.scene.text.*?>

<VBox prefHeight="430.0" prefWidth="640.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="blackjack.FXMLDocumentController">
  <children>
    <AnchorPane maxHeight="-1.0" maxWidth="-1.0" prefHeight="-1.0" prefWidth="-1.0" VBox.vgrow="ALWAYS">
      <children>
            <Label fx:id="labelPlayerTotal" layoutX="510.0" layoutY="335.0" prefHeight="15.0" prefWidth="121.0" text="Playertotal:" />
            <Label fx:id="labelDealerTotal" layoutX="510.0" layoutY="359.0" prefHeight="15.0" prefWidth="112.0" text="Dealertotal:" />
            <TextArea fx:id="dealerArea" layoutY="29.0" prefHeight="159.0" prefWidth="503.0" />
            <TextArea fx:id="playerArea" layoutY="244.0" prefHeight="159.0" prefWidth="503.0" />
            <Button fx:id="stayButton" layoutX="512.0" layoutY="173.0" mnemonicParsing="false" onAction="#drawCardForDealer" prefHeight="25.0" prefWidth="72.0" text="STAY" />
            <Button fx:id="hitButton" layoutX="512.0" layoutY="130.0" mnemonicParsing="false" onAction="#drawCardForPlayer" prefHeight="25.0" prefWidth="72.0" text="HIT" />
            <Label fx:id="labelWinner" layoutX="104.0" layoutY="208.0" prefHeight="15.0" prefWidth="296.0" />
            <MenuBar fx:id="helpBar">
              <menus>
                <Menu mnemonicParsing="false" text="Help">
                  <items>
                    <MenuItem mnemonicParsing="false" onAction="#aboutApplication" text="About" />
                  </items>
                </Menu>
              </menus>
            </MenuBar>
      </children>
    </AnchorPane>
  </children>
</VBox>

Answer 1

You can just hide (i.e. dispose) the window by calling hide() or close() on it. And you can just show a new window with exactly the same code you used before:

                primaryStage.close();

                Stage stage = new Stage();

                root = FXMLLoader.load(getClass().getResource("FXMLDocument.fxml"));

scene = new Scene(root);

stage.setScene(scene);

stage.sizeToScene();
stage.setResizable(false);

stage.show();

But this seems like way too much for what you want to achieve. Why not just replace the root of the existing scene, and use the existing stage?

try {
    scene.setRoot(FXMLLoader.load(getClass().getResource("FXMLDocument.fxml")));
} catch (Exception exc) {
    exc.printStackTrace();
    throw new RuntimeException(exc);
}

Note though that (either way you do this) you have now replaced the root of the scene; the new root does not have the same mouse handler associated with it. If you use the second method, you can just put the handler on the scene (which doesn't change) instead. Or, perhaps better, is that you can define the listener in the FXML and controller:

<VBox prefHeight="430.0" prefWidth="640.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="blackjack.FXMLDocumentController"
fx:id="root"
onMouseClicked="reload">
<!-- ... -->
</VBox>

And the controller:

package blackjack ;

public class FXMLDocumentController {

    // ...

    @FXML
    private VBox root ;

    // ...

    @FXML
    private void reload() throws Exception {

        // Really, it would be way better here to reset the whole UI to its initial
        // state, instead of reloading it from scratch. This should work as a 
        // quick hack though.
        Scene scene = root.getScene();
        scene.setRoot(FXMLLoader.load(Main.class.getResource("FXMLDocument.fmxl")));
    }

    // ...
}