如何从Utility类访问JavaFX PrimaryStage？

Question

当用户单击“保存”按钮时，我正在尝试使用SaveUtil打开FileChooser。 FileChooser需要访问舞台。

您将如何做？

SaveUtil

public class SaveUtil {

public static void saveCanvas(){


    FileChooser fileChooser = new FileChooser();

    //Set extension filter
    FileChooser.ExtensionFilter extFilter =
            new FileChooser.ExtensionFilter("png files (*.png)", "*.png");
    fileChooser.getExtensionFilters().add(extFilter);

    //Show save file dialog
    File file = fileChooser.showSaveDialog(primaryStage);

    if(file != null){
        try {
            WritableImage writableImage = new WritableImage(CANVAS_WIDTH, CANVAS_HEIGHT);
            canvas.snapshot(null, writableImage);
            RenderedImage renderedImage = SwingFXUtils.fromFXImage(writableImage, null);
            ImageIO.write(renderedImage, "png", file);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}
   }

控制器按钮定义：

@FXML
private Canvas fractal;     // This is a drawable area

@FXML
    private void saveCanvas(){
    SaveUtil.saveCanvas();
}

ui.fxml

<Button text="Save" mnemonicParsing="false" onAction="#saveCanvas"/>

主要

public class Main extends Application {


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


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


        String mainwindow = "/fxml/ui.fxml";

        Parent root = null;
        URL mainwindowUrl = null;

        try {

            mainwindowUrl = getClass().getResource(mainwindow);
            root = FXMLLoader.load(mainwindowUrl);
            System.out.println(" mainwindow = " + mainwindow);

        }catch (Exception ex){
            System.out.println( "Exception on FXMLLoader.load()" );
            System.out.println( "  * url: " + mainwindowUrl );
            System.out.println( "  * " + ex );
            System.out.println( "    ----------------------------------------\n" );
            throw ex;
        }

       // Parent root = FXMLLoader.load(getClass().getResource("fxml/ui.fxml"));
        primaryStage.setTitle("Fractal Friend");
        primaryStage.setScene(new Scene(root, 1200, 700));
        primaryStage.show();
    }
}