How to call the public void start(Stage primaryStage) Method from a different class - javafx

Question

I'am new to JavaFX, so my coding is not the best. My programme has one Stage with 2 different Scenes. For a better overview I have created a new class for the second Scene. From this second Scene I want to go back to first one, using a button. The method: primaryStage.setScene(scene) is not working and I dont know why. Can someone please help me? :)
public class Main extends Application {
#Override
public void start(Stage primaryStage) {
try {
GridPane primarygridpane = new GridPane();
Scene scene = new Scene(primarygridpane,400,400);
...
primaryStage.setScene(scene);
primaryStage.show();
} catch(Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
}
public class Harnwegsinfektion {
public static void create (Stage primaryStage){
GridPane secondarygridpane = new GridPane();
Scene scene2 = new Scene(secondarygridpane,400,400);
buttonBack.setOnAction(new EventHandler<ActionEvent>(){
#Override
public void handle(ActionEvent e) {
primaryStage.setScene(scene);
}
});
primaryStage.setScene(scene2);
primaryStage.show();
}
}

Answer 1

The problem is that your scene variable is named scene2 and you are calling setScene() with scene.
I don't really know when and where create() is called, but if you want to go back to the first scene from the button, you have to save the original one before switching :
public static void create (Stage primaryStage){
GridPane secondarygridpane = new GridPane();
Scene scene2 = new Scene(secondarygridpane,400,400);
Scene originalScene=primaryStage.getScene(); //save the previous scene
buttonBack.setOnAction(new EventHandler<ActionEvent>(){
#Override
public void handle(ActionEvent e) {
primaryStage.setScene(originalScene); //go back to the previous scene
}
});
primaryStage.setScene(scene2);
primaryStage.show();
}