JavaFX more Scenes - user-interface

Question

Hi Guys i build a GUI and on this GUI is a Button and when I press the Button a second GUI appears, on the second GUI is also a Button and when i press the Button it goes back
GU1
btn.setOnAction(new EventHandler <ActionEvent>(){
public void handle(ActionEvent arg0) {
try {
new GUI2().start(primaryStage);
} catch (Exception e) {
e.printStackTrace();
}
}
});
My Questions!
Is GUI1 still running when i press the Button?
GUI2
btn.setOnAction(new EventHandler <ActionEvent>(){
public void handle(ActionEvent arg0) {
try {
//back to the main menu
new GUI1().start(primaryStage);
} catch (Exception e) {
e.printStackTrace();
}
}
});
When i press the Button, does it go back to the same instance when beginning the program? Or make it a new Instance witch has the same look, and use it more RAM;
How should it works, when i want to open the second GUI in a external Window

Answer 1

When i press the Button, does it go back to the same instance when beginning the program?
No, a new instance is created based on your code new GUI2().start(primaryStage);. Always remember that thenew keyword ALWAYS creates a new object.
How should it works, when i want to open the second GUI in a external Window?
There are lots of ways to do this.
Method 1
If it happen that you created two applications, both extending the Application class, this method should work.
public class MultiWindowFX {
private static final Logger logger = Logger.getGlobal();
public static class GUI1 extends Application {
private final Button buttonShowGUI2;
private final GUI2 gui2;
public GUI1() {
buttonShowGUI2 = new Button("Show GUI 2");
gui2 = new GUI2();
}
public Button getButtonShowGUI2() {
return buttonShowGUI2;
}
#Override
public void start(Stage primaryStage) throws Exception {
//add an action event on GUI2's buttonShowGUI1 to send front GUI1
gui2.getButtonShowGUI1().setOnAction(gui2ButtonEvent -> {
if (primaryStage.isShowing()) primaryStage.toFront();
else primaryStage.show();
});
//button with action to show GUI 2
buttonShowGUI2.setOnAction(actionEvent -> {
try {
if (gui2.getPrimaryStage() == null) gui2.start(new Stage());
else gui2.getPrimaryStage().toFront();
} catch (Exception ex) {
logger.log(Level.SEVERE, null, ex);
}
});
//set scene and its root
Pane root = new StackPane(buttonShowGUI2);
Scene stageScene = new Scene(root, 400, 250);
//set stage
primaryStage.setScene(stageScene);
primaryStage.centerOnScreen();
primaryStage.setTitle("GUI 1");
primaryStage.show();
}
public static void launchApp(String... args) {
GUI1.launch(args);
}
}
public static class GUI2 extends Application {
private Stage primaryStage;
private final Button buttonShowGUI1;
public GUI2() {
buttonShowGUI1 = new Button("Show GUI 1");
}
public Button getButtonShowGUI1() {
return buttonShowGUI1;
}
public Stage getPrimaryStage() {
return primaryStage;
}
#Override
public void start(Stage primaryStage) throws Exception {
//get stage reference
this.primaryStage = primaryStage;
//set scene and its root
Pane root = new StackPane(buttonShowGUI1);
Scene stageScene = new Scene(root, 400, 250);
//set stage
primaryStage.setScene(stageScene);
primaryStage.centerOnScreen();
primaryStage.setTitle("GUI 2");
primaryStage.show();
}
public static void launchApp(String... args) {
GUI2.launch(args);
}
}
public static void main(String... args) {
GUI1.launchApp(args);
}
}
Method 2
For me, this is the best approach especially if you want window ownership and modality works.
public class GUI1 extends Application {
#Override
public void start(Stage primaryStage) {
Button btn = new Button();
btn.setText("Show GUI2");
btn.setOnAction(actionEvent -> {
//prepare gui2
Stage gui2Stage = createGUI2();
//set window modality and ownership
gui2Stage.initModality(Modality.APPLICATION_MODAL);
gui2Stage.initOwner(primaryStage);
//show
gui2Stage.show();
});
StackPane root = new StackPane();
root.getChildren().add(btn);
Scene scene = new Scene(root, 400, 250);
primaryStage.setTitle("GUI 1");
primaryStage.setScene(scene);
primaryStage.show();
}
private Stage createGUI2() {
Button btn = new Button();
btn.setText("Show GUI1");
StackPane root = new StackPane();
root.getChildren().add(btn);
Scene scene = new Scene(root, 300, 150);
Stage gui2Stage = new Stage();
gui2Stage.setTitle("GUI 2");
gui2Stage.setScene(scene);
//add an action event to GUI2's button, which hides GUI2 and refocuses to GUI1
btn.setOnAction(actionEvent -> gui2Stage.hide());
return gui2Stage;
}
public static void main(String[] args) {
launch(args);
}
}
...and among other methods. Choose the approach that fits to your requirements.