TimelineAnimationController.java

// TimelineAnimationController.java
// Bounce a circle around a window using a Timeline animation. 
import java.security.SecureRandom;
import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.fxml.FXML;
import javafx.geometry.Bounds;
import javafx.scene.layout.Pane;
import javafx.scene.shape.Circle;
import javafx.util.Duration;

public class TimelineAnimationController {
   @FXML Circle c;
   @FXML Pane pane;
   
   public void initialize() {
      SecureRandom random = new SecureRandom();
           
      // define a timeline animation
      Timeline timelineAnimation = new Timeline(
         new KeyFrame(Duration.millis(10), 
            new EventHandler<ActionEvent>() {
               int dx = 1 + random.nextInt(5);
               int dy = 1 + random.nextInt(5);
      
               // move the circle by the dx and dy amounts
               @Override
               public void handle(final ActionEvent e) {
                  c.setLayoutX(c.getLayoutX() + dx);
                  c.setLayoutY(c.getLayoutY() + dy);
                  Bounds bounds = pane.getBoundsInLocal();

                  if (hitRightOrLeftEdge(bounds)) {
                     dx *= -1;
                  }

                  if (hitTopOrBottom(bounds)) {
                     dy *= -1;
                  }
               }
            }
         )
      );

      // indicate that the timeline animation should run indefinitely
      timelineAnimation.setCycleCount(Timeline.INDEFINITE);
      timelineAnimation.play();
   }
   
   // determines whether the circle hit the left or right of the window
   private boolean hitRightOrLeftEdge(Bounds bounds) {
      return (c.getLayoutX() <= (bounds.getMinX() + c.getRadius())) ||
         (c.getLayoutX() >= (bounds.getMaxX() - c.getRadius()));
   }

   // determines whether the circle hit the top or bottom of the window
   private boolean hitTopOrBottom(Bounds bounds) {
      return (c.getLayoutY() <= (bounds.getMinY() + c.getRadius())) ||
         (c.getLayoutY() >= (bounds.getMaxY() - c.getRadius()));
   }
}