为什么我的场景在更改场景（JavaFX）时不弹出？

Question

我在第一个场景上有一个简单的按钮，应该会导致第二个场景。当我点击按钮时，它改变场景，但只显示一个空白屏幕。如果我关闭原始舞台，然后显示一个包含新场景的新舞台，它会正常工作，但我不想打开一个新窗口。

这是我的控制器类：

public class TitleController implements Initializable {

    @FXML
    private Button startButton;

    @Override
    public void initialize(URL location, ResourceBundle resources) {

    }

    //When next/start/main buttons are clicked, transition scene
    public void transitionScenes() throws IOException{
        Stage stage;
        Stage newStage;
        Parent root;
        stage = (Stage) startButton.getScene().getWindow();
        root = FXMLLoader.load(getClass().getResource("Round_1.fxml"));
        Scene scene = new Scene(root);
        stage.setScene(scene);
        stage.show();
    }
}   

主类：

public class Main extends Application{

public void start(Stage primaryStage) throws Exception{
    Parent root =   FXMLLoader.load(getClass().getResource("/fxml/Title_Screen.fxml"));
    Scene scene = new Scene(root);
    primaryStage.setScene(scene);
    primaryStage.show();
}

public static void main(String[] args) {
    launch(args); 
}
}

Answer 1

它对我有用，当我像这样切换场景时：

public class TestApp extends Application {

    @Override
    public void start(Stage primaryStage) throws IOException {

        Button btnChangeScene = new Button("change scene");
        Button btnChangeSceneBack = new Button("change sceneBack");

        btnChangeScene.setOnAction(e -> {
            StackPane root = new StackPane(btnChangeSceneBack);
            root.setStyle("-fx-background-color: orange");
            Scene scene = new Scene(root, 300, 300);
            Stage stage = (Stage) btnChangeScene.getScene().getWindow();
            stage.setScene(scene);
        });


        StackPane root = new StackPane(btnChangeScene);
        Scene scene = new Scene(root, 300, 300);

        btnChangeSceneBack.setOnAction(e -> {
            primaryStage.setScene(scene);
        });

        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}