JavaFX Timeline play image animation

import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.StackPane;
import javafx.scene.media.Media;
import javafx.scene.media.MediaPlayer;
import javafx.stage.Stage;
import javafx.util.Duration;

public class Main extends Application {
   protected TextField tfSpeed = new TextField();
   protected TextField tfPrefix = new TextField();
   protected TextField tfNumberOfImages = new TextField();
   protected TextField tfURL = new TextField();
   protected StackPane paneForImage = new StackPane();
   protected Timeline animation;
   protected int n = 1;

   @Override//from ww w.  j av  a  2s.c  o m
   public void start(Stage primaryStage) {
      final int COLUMN_COUNT = 27;
      tfSpeed.setPrefColumnCount(COLUMN_COUNT);
      tfPrefix.setPrefColumnCount(COLUMN_COUNT);
      tfNumberOfImages.setPrefColumnCount(COLUMN_COUNT);
      tfURL.setPrefColumnCount(COLUMN_COUNT);

      // Create a button
      Button btStart = new Button("Start Animation");

      // Create a grid pane for labels and text fields
      GridPane paneForInfo = new GridPane();
      paneForInfo.setAlignment(Pos.CENTER);
      paneForInfo.add(new Label("Enter information for animation"), 0, 0);
      paneForInfo.add(new Label("Animation speed in milliseconds"), 0, 1);
      paneForInfo.add(tfSpeed, 1, 1);
      paneForInfo.add(new Label("Image file prefix"), 0, 2);
      paneForInfo.add(tfPrefix, 1, 2);
      paneForInfo.add(new Label("Number of images"), 0, 3);
      paneForInfo.add(tfNumberOfImages, 1, 3);
      paneForInfo.add(new Label("Audio file URL"), 0, 4);
      paneForInfo.add(tfURL, 1, 4);

      // Create a border pane
      BorderPane pane = new BorderPane();
      pane.setBottom(paneForInfo);
      pane.setCenter(paneForImage);
      pane.setTop(btStart);
      pane.setAlignment(btStart, Pos.TOP_RIGHT);

      // Create animation
      animation = new Timeline(new KeyFrame(Duration.millis(1000), e -> nextImage()));
      animation.setCycleCount(Timeline.INDEFINITE);

      // Create and register the handler
      btStart.setOnAction(e -> {
         if (tfURL.getText().length() > 0) {
            MediaPlayer mediaPlayer = new MediaPlayer(new Media(tfURL.getText()));
            mediaPlayer.play();
         }
         if (tfSpeed.getText().length() > 0)
            animation.setRate(Integer.parseInt(tfSpeed.getText()));
         animation.play();
      });

      // Create a scene and place it in the stage
      Scene scene = new Scene(pane, 550, 680);
      primaryStage.setTitle("java2s.com");
      primaryStage.setScene(scene);
      primaryStage.show();
   }

   /** Place imageView in pane */
   private void getImage() {
      paneForImage.getChildren().clear();
      paneForImage.getChildren().add(new ImageView(new Image("http://your" + tfPrefix.getText() + n + ".gif")));
   }

   /** Load next image */
   private void nextImage() {
      n = n < Integer.parseInt(tfNumberOfImages.getText()) ? n += 1 : 1;
      getImage();
   }
}