Java 如何使用路径过渡方法使 node 绕圆旋转

你可以:

• 遵循一条路径，并使用这条路径用PathTransition度环绕某个物体.

或

• 使用Timeline设置Rotate transform about a pivot point的动画.

2D场景中的路径动画

该2D示例演示了在时间轴中同时使用路径变换和旋转技术.

import javafx.animation.*;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.Background;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.transform.Rotate;
import javafx.stage.Stage;
import javafx.util.Duration;

public class SolApp extends Application {
    private static final double S = 400, C = S / 2, O = S * 3/8;
    private static final Duration T = Duration.seconds(10);
    private static final Color INDIA_INK = Color.web("#3c3f4a");

    @Override
    public void start(Stage stage) {
        Circle sun = new Circle(
                C, C,
                S/10,
                Color.或ANGERED
        );
        Circle earth = new Circle(
                C + O, C,
                S/40,
                Color.PALETURQUOISE
        );

        Circle orbit = new Circle(C, C, O);
        orbit.setFill(null);
        orbit.setStroke(Color.GREEN);
        orbit.setStrokeWidth(2);

        Pane space = new Pane(sun, orbit, earth);
        space.setPrefSize(S, S);
        space.setBackground(Background.fill(INDIA_INK));

//        Animation orbiter = getTimelineOrbiter(earth);
        Animation orbiter = getPathTransitionOrbiter(orbit, earth);

        stage.setScene(new Scene(space));
        stage.show();

        orbiter.play();
    }

    private static Transition getPathTransitionOrbiter(Circle orbit, Circle earth) {
        PathTransition orbiter = new PathTransition(T, orbit, earth);
        
        orbiter.setInterpolator(Interpolator.LINEAR);
        orbiter.setCycleCount(Animation.INDEFINITE);
        
        return orbiter;
    }

    private static Timeline getTimelineOrbiter(Circle earth) {
        Rotate rotate = new Rotate();
        rotate.setPivotX(C);
        rotate.setPivotY(C);

        earth.getTransforms().add(rotate);

        Timeline orbiter = new Timeline(
                new KeyFrame(
                        Duration.ZERO,
                        new KeyValue(
                                rotate.angleProperty(),
                                0
                        )
                ),
                new KeyFrame(
                        T,
                        new KeyValue(
                                rotate.angleProperty(),
                                360
                        )
                )
        );
        orbiter.setCycleCount(Animation.INDEFINITE);

        return orbiter;
    }

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

在路径上定位 node

如果要调整环游的起点，可以在播放轨道器动画之前应用以下行，根据需要调整0到1之间的除数.

orbiter.jumpTo(T.divide(.17));

这将允许您沿任意路径将 node 放置在任何位置(即使您没有沿路径设置动画).

确定 node 的方向

对于圆和球体(如此处示例中的圆和球体)，您不会注意到 node 方向，但对于非对称 node ，您可能希望将 node 设置为orient，以使其在放置在路径上或沿路径移动时指向所需的方向.

3D场景中的路径动画

同样的技术也适用于3D场景中的动画对象.

import javafx.animation.*;
import javafx.application.Application;
import javafx.geometry.Point3D;
import javafx.scene.*;
import javafx.scene.paint.*;
import javafx.scene.shape.*;
import javafx.scene.transform.Rotate;
import javafx.stage.Stage;
import javafx.util.Duration;

public class SolAppThreeD extends Application {
    private static final double S = 400, C = S / 2, O = S * 3/8;
    private static final Duration T = Duration.seconds(10);
    private static final Color INDIA_INK = Color.web("#3c3f4a");

    @Override
    public void start(Stage stage) {
        Sphere sun = new Sphere(
                S/10
        );
        sun.setMaterial(new PhongMaterial(Color.或ANGERED));
        sun.setTranslateX(C);
        sun.setTranslateY(C);

        PointLight sunsRadiance = new PointLight(Color.LIGHTYELLOW);
        sunsRadiance.translateXProperty().bind(sun.translateXProperty());
        sunsRadiance.translateYProperty().bind(sun.translateYProperty());
        sunsRadiance.translateZProperty().bind(sun.translateZProperty());

        Sphere earth = new Sphere(
                S/40
        );
        earth.setMaterial(new PhongMaterial(Color.DARKTURQUOISE));
        earth.setTranslateX(C + O);
        earth.setTranslateY(C);

        // an f(xyz) Torus could be used instead here for higher fidelity.
        //   https://github.com/FXyz/FXyzLib/blob/master/src/org/fxyz/shapes/Torus.java
        Circle orbit = new Circle(C, C, O);
        orbit.setFill(null);
        orbit.setStroke(Color.GREEN.deriveColor(0, 1, 1, .8));
        orbit.setStrokeWidth(4);

        Animation orbiter = getPathTransitionOrbiter(orbit, earth);

        Group space = new Group(sun, sunsRadiance, orbit, earth);

        PerspectiveCamera camera = new PerspectiveCamera();

        DirectionalLight cameraLight = new DirectionalLight(Color.GRAY);
        cameraLight.translateXProperty().bind(camera.translateXProperty());
        cameraLight.translateYProperty().bind(camera.translateYProperty());
        cameraLight.translateZProperty().bind(camera.translateZProperty());

        Rotate xform = new Rotate(-80, new Point3D(1, 0, 0));
        xform.setPivotX(C);
        xform.setPivotY(C);
        space.getTransforms().add(xform);

        Group root = new Group(cameraLight, space);
        Scene scene = new Scene(root, S, S, true, SceneAntialiasing.BALANCED);
        scene.setCamera(camera);
        scene.setFill(INDIA_INK);
        stage.setScene(scene);
        stage.show();

        orbiter.play();
    }

    private static Transition getPathTransitionOrbiter(Circle orbit, Node satellite) {
        PathTransition orbiter = new PathTransition(T, orbit, satellite);
        
        orbiter.setInterpolator(Interpolator.LINEAR);
        orbiter.setCycleCount(Animation.INDEFINITE);
        
        return orbiter;
    }

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

Using an AnimationTimer

第三种(更复杂的)技术(此处未显示)将设置为use an AnimationTimer，每次调用计时器中的handle方法以更新场景时，计算和调整 node 的平移属性.此技术通常用于游戏循环或物理模型中，其中使用速度向量对对象进行建模，速度向量根据重力、碰撞和反弹等物理属性更新其位置.