Best practice to create views

Question

Hi,
I've a question about best practice to develop a large application with many complex views.
Typically at each time only one views is displayed. User can go from a view to another using a menu bar.
Every view is build with fxml, so my question is about how to create views and how switch from one to another.
Actually I load fxml every time the view is required:
FXMLLoader loader = new FXMLLoader();
InputStream in = MyController.class.getResourceAsStream("MyView.fxml");
loader.setBuilderFactory(new JavaFXBuilderFactory());
loader.setLocation(OptixController.class.getResource("MyView.fxml"));
BorderPane page;
try {
     page = (BorderPane) loader.load(in);
     } finally {
          if (in != null) {
               in.close();
// appController = loader.getController();
Scene scene = new Scene(page, MINIMUM_WINDOW_WIDTH, MINIMUM_WINDOW_HEIGHT);
scene.getStylesheets().add("it/myapp/Mycss.css");
stage.setScene(scene);
stage.sizeToScene();
stage.setScene(scene);
stage.sizeToScene();
stage.centerOnScreen();
stage.show();My questions:
1- is a good practice reload every time the fxml to design the view?
2- is a good practice create every time a new Scene or to have an unique scene in the app and every time clear all elements in it and set the new view?
3- the views should be keep in memory to avoid performace issue or it is a mistake? I think that every time a view should be destroy in order to free memory.
Thanks very much
Edited by: drenda81 on 21-mar-2013 10.41

Answer 1

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My questions:
1- is a good practice reload every time the fxml to design the view?
2- is a good practice create every time a new Scene or to have an unique scene in the app and every time clear all elements in it and set the new view?
3- the views should be keep in memory to avoid performace issue or it is a mistake? I think that every time a view should be destroy in order to free memory.
In choosing between 1 and 3 above, I think either is fine. Loading the FXML on demand every time will be slightly slower, but assuming you are not doing something unusual such as loading over a network connection it won't be noticeable to the user. Loading all views at startup and keeping them in memory uses more memory, but again, it's unlikely to be an issue. I would choose whichever is easier to code (probably loading on demand).
In choosing between reusing a Scene or creating a new one each time, I would reuse the Scene. "Clearing all elements in it" only needs you to call scene.setRoot(...) and pass in the new view. Since the Scene has a mutable root property, you may as well make use of it and save the (small) overhead of instantiating a new Scene each time. You might consider exposing a currentView property somewhere (say, in your main controller, or model if you have a separate model class) and binding the Scene's root property to it. Something like:
public class MainController {
  private final ObjectProperty<Parent> currentView ;
  public MainController() {
    currentView = new SimpleObjectProperty<Parent>(this, "currentView");
  public void initialize() {
    currentView.set(loadView("StartView.fxml"));
  public ObjectProperty<Parent> currentViewProperty() {
    return currentView ;
  // event handler to load View1:
  @FXML
  private void loadView1() {
    currentView.set(loadView("View1.fxml"));
  // similarly for other views...
  private Parent loadView(String fxmlFile) {
    try {
     Parent view = FXMLLoader.load(getClass().getResource(fxmlFile));
     return view ;
    } catch (...) { ... }
}Then your application can do this:
@Override
public void start(Stage primaryStage) {
   Scene scene = new Scene();
   FXMLLoader loader = new FXMLLoader(getClass().getResource("Main.fxml"));
   MainController controller = (MainController) loader.getController();
   scene.rootProperty().bind(controller.currentViewProperty());
   // set scene in stage, etc...
}This means your Controller doesn't need to know about the Scene, which maintains a nice decoupling.