JavaFx 8-相对于鼠标位置缩放/缩放ScrollPane

• Z时代
• 2024-01-10
• 分类：问答

我需要在滚动窗格上相对于鼠标位置放大/缩小。

我目前通过将内容包装在一个组中并缩放组本身来实现缩放功能。我用自定义枢轴创建一个新的Scale对象。（枢轴设置为鼠标位置）

这在Group的初始比例为1.0的情况下非常适用，但是之后的缩放比例无法沿正确的方向缩放-我相信这是因为Group缩放后相对鼠标位置会发生变化。

我的代码：

@Override
public void initialize(URL location, ResourceBundle resources) {
    Delta initial_mouse_pos = new Delta();
    anchorpane.setOnScrollStarted(event -> {
        initial_mouse_pos.x = event.getX();
        initial_mouse_pos.y = event.getY();
    });
    anchorpane.setOnScroll(event -> {
        double zoom_fac = 1.05;
        double delta_y = event.getDeltaY();
        if(delta_y < 0) {
            zoom_fac = 2.0 - zoom_fac;
        }
        Scale newScale = new Scale();
        newScale.setPivotX(initial_mouse_pos.x);
        newScale.setPivotY(initial_mouse_pos.y);
        newScale.setX( content_group.getScaleX() * zoom_fac );
        newScale.setY( content_group.getScaleY() * zoom_fac );
        content_group.getTransforms().add(newScale);
        event.consume();
    });
}
private class Delta { double x, y; }

如何在不同的缩放级别上获得正确的鼠标位置？有没有一种更简单的缩放ScrollPane的完全不同的方法？

回答：

这是一个 JavaFX ScrollPane：

import javafx.geometry.Bounds;
import javafx.geometry.Point2D;
import javafx.geometry.Pos;
import javafx.scene.Group;
import javafx.scene.Node;
import javafx.scene.control.ScrollPane;
import javafx.scene.layout.VBox;
public class ZoomableScrollPane extends ScrollPane {
    private double scaleValue = 0.7;
    private double zoomIntensity = 0.02;
    private Node target;
    private Node zoomNode;
    public ZoomableScrollPane(Node target) {
        super();
        this.target = target;
        this.zoomNode = new Group(target);
        setContent(outerNode(zoomNode));
        setPannable(true);
        setHbarPolicy(ScrollPane.ScrollBarPolicy.NEVER);
        setVbarPolicy(ScrollPane.ScrollBarPolicy.NEVER);
        setFitToHeight(true); //center
        setFitToWidth(true); //center
        updateScale();
    }
    private Node outerNode(Node node) {
        Node outerNode = centeredNode(node);
        outerNode.setOnScroll(e -> {
            e.consume();
            onScroll(e.getTextDeltaY(), new Point2D(e.getX(), e.getY()));
        });
        return outerNode;
    }
    private Node centeredNode(Node node) {
        VBox vBox = new VBox(node);
        vBox.setAlignment(Pos.CENTER);
        return vBox;
    }
    private void updateScale() {
        target.setScaleX(scaleValue);
        target.setScaleY(scaleValue);
    }
    private void onScroll(double wheelDelta, Point2D mousePoint) {
        double zoomFactor = Math.exp(wheelDelta * zoomIntensity);
        Bounds innerBounds = zoomNode.getLayoutBounds();
        Bounds viewportBounds = getViewportBounds();
        // calculate pixel offsets from [0, 1] range
        double valX = this.getHvalue() * (innerBounds.getWidth() - viewportBounds.getWidth());
        double valY = this.getVvalue() * (innerBounds.getHeight() - viewportBounds.getHeight());
        scaleValue = scaleValue * zoomFactor;
        updateScale();
        this.layout(); // refresh ScrollPane scroll positions & target bounds
        // convert target coordinates to zoomTarget coordinates
        Point2D posInZoomTarget = target.parentToLocal(zoomNode.parentToLocal(mousePoint));
        // calculate adjustment of scroll position (pixels)
        Point2D adjustment = target.getLocalToParentTransform().deltaTransform(posInZoomTarget.multiply(zoomFactor - 1));
        // convert back to [0, 1] range
        // (too large/small values are automatically corrected by ScrollPane)
        Bounds updatedInnerBounds = zoomNode.getBoundsInLocal();
        this.setHvalue((valX + adjustment.getX()) / (updatedInnerBounds.getWidth() - viewportBounds.getWidth()));
        this.setVvalue((valY + adjustment.getY()) / (updatedInnerBounds.getHeight() - viewportBounds.getHeight()));
    }
}

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