javafx – 在已经缩放的节点上的枢轴点进行缩放

我正在尝试使用可缩放/可绘制的画布创建应用程序.

特征：

>使用鼠标滚轮放大/缩小转动点
>使用鼠标左键在画布上拖动节点
>用鼠标右键拖动整个画布

只要您在比例尺1开始缩放,就可以在枢轴点进行缩放.将鼠标放在网格点上并滚动鼠标滚轮.枢轴点将保持开始缩放的位置.

问题：

当您放大时,将鼠标移动到另一点并再次放大,然后在初始鼠标位置,枢轴点移动,缩放不再发生.

例：

以下是代码：

import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.Group;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.control.Label;
import javafx.scene.input.MouseEvent;
import javafx.scene.input.ScrollEvent;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.shape.Rectangle;
import javafx.scene.transform.Scale;
import javafx.stage.Stage;

/**
 * The canvas which holds all of the nodes of the application.
 */
class PannableCanvas extends Pane {

    Scale scaleTransform;

    public PannableCanvas() {

        setPrefSize(600,600);
        setStyle("-fx-background-color: lightgrey; -fx-border-color: blue;");

        // add scale transform
        scaleTransform = new Scale( 1.0,1.0);
        getTransforms().add( scaleTransform);

        // logging
        addEventFilter(MouseEvent.MOUSE_PRESSED,event -> { 
            System.out.println( 
                    "canvas event: " + ( ((event.getSceneX() - getBoundsInParent().getMinX()) / getScale()) + ",scale: " + getScale())
                    );
            System.out.println( "canvas bounds: " + getBoundsInParent());   
                });

    }

    /**
     * Add a grid to the canvas,send it to back
     */
    public void addGrid() {

        double w = getBoundsInLocal().getWidth();
        double h = getBoundsInLocal().getHeight();

        // add grid
        Canvas grid = new Canvas(w,h);

        // don't catch mouse events
        grid.setMouseTransparent(true);

        GraphicsContext gc = grid.getGraphicsContext2D();

        gc.setStroke(Color.GRAY);
        gc.setLineWidth(1);

        // draw grid lines
        double offset = 50;
        for( double i=offset; i < w; i+=offset) {
            // vertical
            gc.strokeLine( i,i,h);
            // horizontal
            gc.strokeLine( 0,w,i);
        }

        getChildren().add( grid);

        grid.toBack();
    }

    public Scale getScaleTransform() {
        return scaleTransform;
    }

    public double getScale() {
        return scaleTransform.getY();
    }

    /**
     * Set x/y scale
     * @param scale
     */
    public void setScale( double scale) {
        scaleTransform.setX(scale);
        scaleTransform.setY(scale);
    }

    /**
     * Set x/y pivot points
     * @param x
     * @param y
     */
    public void setPivot( double x,double y) {
        scaleTransform.setPivotX(x);
        scaleTransform.setPivotY(y);
    }
}


/**
 * Mouse drag context used for scene and nodes.
 */
class DragContext {

    double mouseAnchorX;
    double mouseAnchorY;

    double translateAnchorX;
    double translateAnchorY;

}

/**
 * Listeners for making the nodes draggable via left mouse button. Considers if parent is zoomed.
 */
class NodeGestures {

    private DragContext nodeDragContext = new DragContext();

    PannableCanvas canvas;

    public NodeGestures( PannableCanvas canvas) {
        this.canvas = canvas;

    }

    public EventHandler<MouseEvent> getOnMousePressedEventHandler() {
        return onMousePressedEventHandler;
    }

    public EventHandler<MouseEvent> getOnMouseDraggedEventHandler() {
        return onMouseDraggedEventHandler;
    }

    private EventHandler<MouseEvent> onMousePressedEventHandler = new EventHandler<MouseEvent>() {

        public void handle(MouseEvent event) {

            // left mouse button => dragging
            if( !event.isPrimaryButtonDown())
                return;

            nodeDragContext.mouseAnchorX = event.getSceneX();
            nodeDragContext.mouseAnchorY = event.getSceneY();

            Node node = (Node) event.getSource();

            nodeDragContext.translateAnchorX = node.getTranslateX();
            nodeDragContext.translateAnchorY = node.getTranslateY();

        }

    };

    private EventHandler<MouseEvent> onMouseDraggedEventHandler = new EventHandler<MouseEvent>() {
        public void handle(MouseEvent event) {

            // left mouse button => dragging
            if( !event.isPrimaryButtonDown())
                return;

            double scale = canvas.getScale();

            Node node = (Node) event.getSource();

            node.setTranslateX(nodeDragContext.translateAnchorX + (( event.getSceneX() - nodeDragContext.mouseAnchorX) / scale));
            node.setTranslateY(nodeDragContext.translateAnchorY + (( event.getSceneY() - nodeDragContext.mouseAnchorY) / scale));

            event.consume();

        }
    };
}

/**
 * Listeners for making the scene's canvas draggable and zoomable
 */
class SceneGestures {

    private static final double MAX_SCALE = 10.0d;
    private static final double MIN_SCALE = .1d;

    private DragContext sceneDragContext = new DragContext();

    PannableCanvas canvas;

    public SceneGestures( PannableCanvas canvas) {
        this.canvas = canvas;
    }

    public EventHandler<MouseEvent> getOnMousePressedEventHandler() {
        return onMousePressedEventHandler;
    }

    public EventHandler<MouseEvent> getOnMouseDraggedEventHandler() {
        return onMouseDraggedEventHandler;
    }

    public EventHandler<ScrollEvent> getOnScrollEventHandler() {
        return onScrollEventHandler;
    }

    private EventHandler<MouseEvent> onMousePressedEventHandler = new EventHandler<MouseEvent>() {

        public void handle(MouseEvent event) {

            // right mouse button => panning
            if( !event.isSecondaryButtonDown())
                return;

            sceneDragContext.mouseAnchorX = event.getSceneX();
            sceneDragContext.mouseAnchorY = event.getSceneY();

            sceneDragContext.translateAnchorX = canvas.getTranslateX();
            sceneDragContext.translateAnchorY = canvas.getTranslateY();

        }

    };

    private EventHandler<MouseEvent> onMouseDraggedEventHandler = new EventHandler<MouseEvent>() {
        public void handle(MouseEvent event) {

            // right mouse button => panning
            if( !event.isSecondaryButtonDown())
                return;

            canvas.setTranslateX(sceneDragContext.translateAnchorX + event.getSceneX() - sceneDragContext.mouseAnchorX);
            canvas.setTranslateY(sceneDragContext.translateAnchorY + event.getSceneY() - sceneDragContext.mouseAnchorY);

            event.consume();
        }
    };

    /**
     * Mouse wheel handler: zoom to pivot point
     */
    private EventHandler<ScrollEvent> onScrollEventHandler = new EventHandler<ScrollEvent>() {

        @Override
        public void handle(ScrollEvent event) {

            double delta = 1;

            double scale = canvas.getScale(); // currently we only use Y,same value is used for X
            double oldScale = scale;

            if (event.getDeltaY() < 0)
                scale -= delta;
            else
                scale += delta;

            if (scale <= MIN_SCALE) {
                scale = MIN_SCALE;
            } else if (scale >= MAX_SCALE) {
                scale = MAX_SCALE;
            }

            // pivot value must be untransformed,i. e. without scaling
            canvas.setPivot( 
                    ((event.getSceneX() - canvas.getBoundsInParent().getMinX()) / oldScale),((event.getSceneY() - canvas.getBoundsInParent().getMinY()) / oldScale)
                    );

            canvas.setScale( scale);

            System.out.println( "new pivot x: " + canvas.scaleTransform.getPivotX() + "/" + canvas.scaleTransform.getPivotY() + ",new scale: " + scale);
            System.out.println( "bounds: " + canvas.getBoundsInParent());       

            event.consume();

        }

    };


}

/**
 * An application with a zoomable and pannable canvas.
 */
public class ScrollApplication extends Application {
    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage stage) {

        Group group = new Group();

        // create canvas
        PannableCanvas canvas = new PannableCanvas();

        // we don't want the canvas on the top/left in this example => just
        // translate it a bit
        canvas.setTranslateX(100);
        canvas.setTranslateY(100);

        // create sample nodes which can be dragged
        NodeGestures nodeGestures = new NodeGestures( canvas);

        Label label1 = new Label("Draggable node 1");
        label1.setTranslateX(10);
        label1.setTranslateY(10);
        label1.addEventFilter( MouseEvent.MOUSE_PRESSED,nodeGestures.getOnMousePressedEventHandler());
        label1.addEventFilter( MouseEvent.MOUSE_DRAGGED,nodeGestures.getOnMouseDraggedEventHandler());

        Label label2 = new Label("Draggable node 2");
        label2.setTranslateX(100);
        label2.setTranslateY(100);
        label2.addEventFilter( MouseEvent.MOUSE_PRESSED,nodeGestures.getOnMousePressedEventHandler());
        label2.addEventFilter( MouseEvent.MOUSE_DRAGGED,nodeGestures.getOnMouseDraggedEventHandler());

        Label label3 = new Label("Draggable node 3");
        label3.setTranslateX(200);
        label3.setTranslateY(200);
        label3.addEventFilter( MouseEvent.MOUSE_PRESSED,nodeGestures.getOnMousePressedEventHandler());
        label3.addEventFilter( MouseEvent.MOUSE_DRAGGED,nodeGestures.getOnMouseDraggedEventHandler());

        Circle circle1 = new Circle( 300,300,50);
        circle1.setStroke(Color.ORANGE);
        circle1.setFill(Color.ORANGE.deriveColor(1,1,0.5));
        circle1.addEventFilter( MouseEvent.MOUSE_PRESSED,nodeGestures.getOnMousePressedEventHandler());
        circle1.addEventFilter( MouseEvent.MOUSE_DRAGGED,nodeGestures.getOnMouseDraggedEventHandler());

        Rectangle rect1 = new Rectangle(100,100);
        rect1.setTranslateX(450);
        rect1.setTranslateY(450);
        rect1.setStroke(Color.BLUE);
        rect1.setFill(Color.BLUE.deriveColor(1,0.5));
        rect1.addEventFilter( MouseEvent.MOUSE_PRESSED,nodeGestures.getOnMousePressedEventHandler());
        rect1.addEventFilter( MouseEvent.MOUSE_DRAGGED,nodeGestures.getOnMouseDraggedEventHandler());

        canvas.getChildren().addAll(label1,label2,label3,circle1,rect1);

        group.getChildren().add(canvas);

        // create scene which can be dragged and zoomed
        Scene scene = new Scene(group,1024,768);

        SceneGestures sceneGestures = new SceneGestures(canvas);
        scene.addEventFilter( MouseEvent.MOUSE_PRESSED,sceneGestures.getOnMousePressedEventHandler());
        scene.addEventFilter( MouseEvent.MOUSE_DRAGGED,sceneGestures.getOnMouseDraggedEventHandler());
        scene.addEventFilter( ScrollEvent.ANY,sceneGestures.getOnScrollEventHandler());

        stage.setScene(scene);
        stage.show();

        canvas.addGrid();

    }
}

显然,枢轴点计算有问题,但我无法弄清楚它是什么,以及如何解决它.

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