JavaFX 2 circle path for animation

Question

How can I create a circle (or ellipse) javafx.scene.shape.Path in JavaFX 2?

I've found some examples using CubicCurveTo:

Path path = new Path();
path.getElements().add(new CubicCurveTo(30, 10, 380, 120, 200, 120));

but I don't understand that Bézier coordinates. I need a full circle path for animations.

Answer 1

You can utilize the ArcTo path element to draw circle or ellipse path:

public class ArcToDemo extends Application {

    private PathTransition pathTransitionEllipse;
    private PathTransition pathTransitionCircle;

    private void init(Stage primaryStage) {
        Group root = new Group();
        primaryStage.setResizable(false);
        primaryStage.setScene(new Scene(root, 600, 460));

        // Ellipse path example
        Rectangle rect = new Rectangle(0, 0, 40, 40);
        rect.setArcHeight(10);
        rect.setArcWidth(10);
        rect.setFill(Color.ORANGE);
        root.getChildren().add(rect);

        Path path = createEllipsePath(200, 200, 50, 100, 45);
        root.getChildren().add(path);

        pathTransitionEllipse = PathTransitionBuilder.create()
                .duration(Duration.seconds(4))
                .path(path)
                .node(rect)
                .orientation(OrientationType.ORTHOGONAL_TO_TANGENT)
                .cycleCount(Timeline.INDEFINITE)
                .autoReverse(false)
                .build();


        // Cirle path example

        Rectangle rect2 = new Rectangle(0, 0, 20, 20);
        rect2.setArcHeight(10);
        rect2.setArcWidth(10);
        rect2.setFill(Color.GREEN);
        root.getChildren().add(rect2);

        Path path2 = createEllipsePath(400, 200, 150, 150, 0);
        root.getChildren().add(path2);

        pathTransitionCircle = PathTransitionBuilder.create()
                .duration(Duration.seconds(2))
                .path(path2)
                .node(rect2)
                .orientation(OrientationType.ORTHOGONAL_TO_TANGENT)
                .cycleCount(Timeline.INDEFINITE)
                .autoReverse(false)
                .build();
    }

    private Path createEllipsePath(double centerX, double centerY, double radiusX, double radiusY, double rotate) {
        ArcTo arcTo = new ArcTo();
        arcTo.setX(centerX - radiusX + 1); // to simulate a full 360 degree celcius circle.
        arcTo.setY(centerY - radiusY);
        arcTo.setSweepFlag(false);
        arcTo.setLargeArcFlag(true);
        arcTo.setRadiusX(radiusX);
        arcTo.setRadiusY(radiusY);
        arcTo.setXAxisRotation(rotate);

        Path path = PathBuilder.create()
                .elements(
                new MoveTo(centerX - radiusX, centerY - radiusY),
                arcTo,
                new ClosePath()) // close 1 px gap.
                .build();
        path.setStroke(Color.DODGERBLUE);
        path.getStrokeDashArray().setAll(5d, 5d);
        return path;
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        init(primaryStage);
        primaryStage.show();
        pathTransitionEllipse.play();
        pathTransitionCircle.play();
    }

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

Good reference of the features of ArcTo is ArcTo (JavaFX 8). Allthough it is version 8, the meanings of the features are similar.
Output: