如何在javafx中保存所选图像？

import javafx.application.Application;
import javafx.embed.swing.SwingFXUtils;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.VBox;
import javafx.stage.FileChooser;
import javafx.stage.Stage;

import javax.imageio.ImageIO;
import java.io.File;
import java.io.IOException;

public class SaveImageExample extends Application {

    @Override
    public void start(Stage primaryStage) {
        Button saveButton = new Button("Save Image");
        ImageView imageView = new ImageView();

        saveButton.setOnAction(event -> {
            FileChooser fileChooser = new FileChooser();
            fileChooser.getExtensionFilters().add(new FileChooser.ExtensionFilter("Image Files", "*.png", "*.jpg", "*.gif"));
            File file = fileChooser.showSaveDialog(primaryStage);

            if (file != null) {
                try {
                    Image selectedImage = imageView.getImage();
                    int width = (int) selectedImage.getWidth();
                    int height = (int) selectedImage.getHeight();
                    WritableImage writableImage = new WritableImage(width, height);
                    PixelWriter pixelWriter = writableImage.getPixelWriter();
                    pixelWriter.setPixels(0, 0, width, height, selectedImage.getPixelReader(), 0, 0);
                    BufferedImage bufferedImage = SwingFXUtils.fromFXImage(writableImage, null);
                    ImageIO.write(bufferedImage, "png", file);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });

        VBox vbox = new VBox(saveButton, imageView);
        Scene scene = new Scene(vbox, 400, 400);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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