Timeline for parabolic trajectory in JavaFX

Question

I\'m sorry, but I continue not understanding. My problem is I know nothing about physics but my teacher assigned to me this project.

private void shoot() {           


        

Answer 1

In a KeyValue, the first parameter should be a WritableValue, e.g. circle.centerXProperty(), which represents the initial coordinate, say x. The second parameter should be a type compatible value, in this case the x coordinate toward which the projectile should move. As the timeline plays, the WritableValue will be updated accordingly. Add a second KeyValue to drive the y coordinate.

In the first example seen here, three instances of KeyValue move a figure from it's initial position to its destination position, which is size units away along each coordinate axis. In this related example, a figure moves form point p1 to p2.

In the example below, a Circle moves parallel to the x axis between 100 and 500. At the same time, that same Circle moves parallel to the y axis between 300 and 100 following the curve() defined by the parabola y = –4(x – ½)² + 1, which has vertex (½, 1) and x intercepts at 0 and 1. This implementation of curve() models a parabolic path on a unit square, as required by the curve() API. You can change the angle of elevation by changing the ratio of height to width in the keys frames, e.g.

KeyValue xKV = new KeyValue(c.centerXProperty(), 200);
KeyValue yKV = new KeyValue(c.centerYProperty(), 0, new Interpolator() {…});

import javafx.animation.Interpolator;
import javafx.animation.KeyFrame;
import javafx.animation.KeyValue;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.shape.Line;
import javafx.stage.Stage;
import javafx.util.Duration;

/**
 * @see https://stackoverflow.com/a/38031826/230513
 */
public class Test extends Application {

    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("Test");
        Group group = new Group();
        Scene scene = new Scene(group, 600, 350);
        scene.setFill(Color.BLACK);
        primaryStage.setScene(scene);
        primaryStage.show();
        Circle c = new Circle(100, 300, 16, Color.AQUA);
        Line l = new Line(100, 300, 500, 300);
        l.setStroke(Color.AQUA);
        group.getChildren().addAll(c, l);
        final Timeline timeline = new Timeline();
        timeline.setCycleCount(Timeline.INDEFINITE);
        timeline.setAutoReverse(false);
        KeyValue xKV = new KeyValue(c.centerXProperty(), 500);
        KeyValue yKV = new KeyValue(c.centerYProperty(), 100, new Interpolator() {
            @Override
            protected double curve(double t) {
                return -4 * (t - .5) * (t - .5) + 1;
            }
        });
        KeyFrame xKF = new KeyFrame(Duration.millis(2000), xKV);
        KeyFrame yKF = new KeyFrame(Duration.millis(2000), yKV);
        timeline.getKeyFrames().addAll(xKF, yKF);
        timeline.play();
    }

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

}