How can a dynamically generated JavaFX scene be changed in a single stage? - javafx

Question

I'm currently working on a project requiring me to switch back and forward between scenes. I have already written some code for it but it isn't as elegant as I wanted to be, especially as there is few flickers when I switch between them and sometimes even the buttons that I have generated simply disappear only to appear once again when yet another scene has been generated. Moreover, the layout I'm using for my application isn't really fixed and I think that using FXML might be not suitable for what I'm doing.
Thank you.
This is what I'm using to change between scenes:
void changeScene(Stage stage,Scene scene){
stage.setScene(scene);
primaryStage.setFullScreen(true);
}

Answer 1

I assume by "switching between scenes" you mean that you want to change the entire content of the existing window.
There are two (very) slightly different ways you can do this. Either create a new Scene and pass it to the Stage's setScene(...) method. Or create the Parent that is the root of the new UI (either by FXML or otherwise), and pass it to the existing Scene's setRoot(...) method. There's no real advantage that I can see of one over the other.
Here's a minimal implementation of the second option. The UI is irrelevant to the question: the important parts are the event handlers for the "Login" button (which switches from the login scene to the main scene) and the "Logout" button (which switches back).
import java.util.stream.IntStream;
import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.beans.property.IntegerProperty;
import javafx.beans.property.SimpleIntegerProperty;
import javafx.geometry.HPos;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.ListView;
import javafx.scene.control.SplitPane;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.ColumnConstraints;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.Priority;
import javafx.scene.text.Font;
import javafx.scene.text.FontWeight;
import javafx.stage.Stage;
public class MinimalSceneSwitchingExample extends Application {
#Override
public void start(Stage primaryStage) {
LoginView loginView = new LoginView();
Scene scene = new Scene(loginView.getView(), 400, 400);
primaryStage.setScene(scene);
primaryStage.show();
}
public static class LoginView {
private final IntegerProperty loginAttempts ;
private final GridPane view ;
public LoginView() {
view = new GridPane();
TextField usernameTF = new TextField("user");
TextField passwordTF = new TextField("pass");
// Login button switches to main view:
Button loginButton = new Button("Login");
loginButton.setOnAction(event -> {
if (usernameTF.getText().equalsIgnoreCase("user")
&& passwordTF.getText().equalsIgnoreCase("pass")) {
// *** Switch to main view: ***
Parent mainView = new MainView().getView();
view.getScene().setRoot(mainView);
} else {
loginAttempts.set(loginAttempts.get()+1);
}
});
// just set up login UI... irrelevant to this example:
loginAttempts = new SimpleIntegerProperty();
usernameTF.setPromptText("Hint: user");
passwordTF.setPromptText("Hint: pass");
view.addRow(0, new Label("Username:"), usernameTF);
view.addRow(1, new Label("Password:"), passwordTF);
Label loginErrorMessage = new Label();
loginErrorMessage.textProperty().bind(
Bindings.when(loginAttempts.isEqualTo(0))
.then("")
.otherwise(Bindings.format("Login incorrect (Attempts: %d)",
loginAttempts)));
view.add(loginErrorMessage, 0, 2, 2, 1);
view.add(loginButton, 0, 3, 2, 1);
ColumnConstraints leftCol = new ColumnConstraints();
leftCol.setHgrow(Priority.NEVER);
leftCol.setHalignment(HPos.RIGHT);
ColumnConstraints rightCol = new ColumnConstraints();
rightCol.setHgrow(Priority.ALWAYS);
rightCol.setHalignment(HPos.LEFT);
view.getColumnConstraints().addAll(leftCol, rightCol);
GridPane.setHalignment(loginErrorMessage, HPos.CENTER);
GridPane.setHalignment(loginButton, HPos.CENTER);
view.setHgap(10);
view.setVgap(16);
view.setAlignment(Pos.CENTER);
}
public Parent getView() {
return view ;
}
}
public static class MainView {
private BorderPane view ;
public MainView() {
view = new BorderPane();
// *** logout button switches back to a login view: ***
Button logoutButton = new Button("Log out");
logoutButton.setOnAction(event ->
view.getScene().setRoot(new LoginView().getView()));
// Arbitrary UI, irrelevant to this example:
SplitPane splitPane = new SplitPane();
ListView<String> listView = new ListView<>();
IntStream.rangeClosed(1, 10)
.mapToObj(Integer::toString)
.map("Item "::concat)
.forEach(listView.getItems()::add);
Label bigLabel = new Label();
bigLabel.textProperty().bind(
listView.getSelectionModel().selectedItemProperty());
bigLabel.setFont(Font.font("Verdana", FontWeight.BOLD, 18));
BorderPane.setAlignment(bigLabel, Pos.CENTER);
BorderPane.setMargin(bigLabel, new Insets(10));
Label details = new Label();
details.textProperty().bind(
Bindings.when(
listView.getSelectionModel().selectedItemProperty().isNull())
.then("")
.otherwise(Bindings.format("This is where you would display "
+ "all sorts of details about %1$s. "
+ "If %1$s were really a model object, you "
+ "might have a GridPane displaying all its "
+ "properties, for example.",
listView.getSelectionModel().selectedItemProperty())));
details.setWrapText(true);
BorderPane detailsPane = new BorderPane(details, bigLabel, null, null, null);
splitPane.getItems().addAll(listView, detailsPane);
view.setCenter(splitPane);
view.setBottom(logoutButton);
BorderPane.setAlignment(logoutButton, Pos.CENTER);
BorderPane.setMargin(logoutButton, new Insets(8));
BorderPane.setMargin(splitPane, new Insets(16));
}
public Parent getView() {
return view ;
}
}
public static void main(String[] args) {
launch(args);
}
}