Controlling Animation Speed

To slow down an animation implemented using AnimationTimer in JavaFX, you can control the rate at which the timer updates the animation by using a time-based approach.

Here’s how you can achieve that:

Note

1. Use a frame duration: Keep track of the time elapsed since the last update, and only update the animation when a certain duration has passed.

2. Adjust the timing factor: You can introduce a timing factor that represents how much you want to slow down the animation.

Here’s an example to illustrate this:

import javafx.animation.AnimationTimer;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.layout.Pane;
import javafx.stage.Stage;

public class SlowDownAnimationExample extends Application {
    private double x = 0;
    private double speed = 2; // Speed of the animation
    private double slowFactor = 0.5; // Slow down factor (0.5 = half speed)
    private long lastUpdate = 0;

    @Override
    public void start(Stage primaryStage) {
        Pane pane = new Pane();
        Circle circle = new Circle(20, Color.BLUE);
        pane.getChildren().add(circle);

        AnimationTimer timer = new AnimationTimer() {
            @Override
            public void handle(long now) {
                if (lastUpdate == 0) {
                    lastUpdate = now; // Initialize lastUpdate
                }
                // Calculate the elapsed time in seconds
                double elapsedTime = (now - lastUpdate) / 1_000_000_000.0;

                // Only update the animation based on the slow factor
                if (elapsedTime >= slowFactor) {
                    x += speed; // Update position based on speed
                    circle.setCenterX(x);
                    lastUpdate = now; // Reset lastUpdate
                }
            }
        };

        timer.start();

        Scene scene = new Scene(pane, 400, 300);
        primaryStage.setTitle("Slow Down Animation Example");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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

Explanation:

• lastUpdate: This variable keeps track of the last time the animation was updated.
• elapsedTime: This is calculated each frame to determine how much time has passed since the last update.
• slowFactor: This controls how often the animation updates. A value of 0.5 means the animation updates only every half a second.
• The circle’s position is updated only if the elapsed time is greater than or equal to the slowFactor.

By adjusting the slowFactor, you can control how slow or fast the animation runs.