我有一个应用程序需要在ScrollPane内部进行缩放，但是使用当前的方法仍然存在两个挑战。为了复制问题，我编写了一个小应用程序ZoomApp，在下面可以找到其代码。其有限的功能允许在一些任意形状上进行放大和缩小（使用Ctrl +鼠标滚轮）。当缩放内容超出窗口范围时，滚动条应该出现。
挑战1：当滚动条因为innerGroup大小的缩放而出现时，ScrollEvent不再到达我的ZoomHandler。相反，我们开始向下滚动窗口，直到达到底部，再次缩放时才能正常工作。我认为可能
scrollPane.setPannable(false);
会有所不同，但没关系。如何避免这种不必要的行为？
挑战2. 如果不用在innerGroup的左上角绘制一个带有所需差值的像素，那么我该如何将其置中于scrollPane中?
顺便提一句，根据ScrollPane的JavaDoc: "如果应用程序希望滚动基于节点的可视范围（对于缩放内容等），则需要在一个Group中包装滚动节点"。这就是为什么我在ScrollPane内部有一个innerGroup和outerGroup的原因。
任何指导我找到解决方案的建议都将不胜感激，因为我是JavaFX的新手。
import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.Group;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.SceneBuilder;
import javafx.scene.control.ScrollPane;
import javafx.scene.input.ScrollEvent;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;
/**
* Demo of a challenge I have with zooming inside a {@code ScrollPane}.
* <br>
* I am running JavaFx 2.2 on a Mac. {@code java -version} yields:
* <pre>
* java version "1.7.0_09"
* Java(TM) SE Runtime Environment (build 1.7.0_09-b05)
* Java HotSpot(TM) 64-Bit Server VM (build 23.5-b02, mixed mode)
* </pre>
* 6 rectangles are drawn, and can be zoomed in and out using either
* <pre>
* Ctrl + Mouse Wheel
* or Ctrl + 2 fingers on the pad.
* </pre>
* It reproduces a problem I experience inside an application I am writing.
* If you magnify to {@link #MAX_SCALE}, an interesting problem occurs when you try to zoom back to {@link #MIN_SCALE}. In the beginning
* you will see that the {@code scrollPane} scrolls and consumes the {@code ScrollEvent} until we have scrolled to the bottom of the window.
* Once the bottom of the window is reached, it behaves as expected (or at least as I was expecting).
*
* @author Skjalg Bjørndal
* @since 2012.11.05
*/
public class ZoomApp extends Application {
private static final int WINDOW_WIDTH = 800;
private static final int WINDOW_HEIGHT = 600;
private static final double MAX_SCALE = 2.5d;
private static final double MIN_SCALE = .5d;
private class ZoomHandler implements EventHandler<ScrollEvent> {
private Node nodeToZoom;
private ZoomHandler(Node nodeToZoom) {
this.nodeToZoom = nodeToZoom;
}
@Override
public void handle(ScrollEvent scrollEvent) {
if (scrollEvent.isControlDown()) {
final double scale = calculateScale(scrollEvent);
nodeToZoom.setScaleX(scale);
nodeToZoom.setScaleY(scale);
scrollEvent.consume();
}
}
private double calculateScale(ScrollEvent scrollEvent) {
double scale = nodeToZoom.getScaleX() + scrollEvent.getDeltaY() / 100;
if (scale <= MIN_SCALE) {
scale = MIN_SCALE;
} else if (scale >= MAX_SCALE) {
scale = MAX_SCALE;
}
return scale;
}
}
public static void main(String[] args) {
launch(args);
}
@Override
public void start(Stage stage) throws Exception {
final Group innerGroup = createSixRectangles();
final Group outerGroup = new Group(innerGroup);
final ScrollPane scrollPane = new ScrollPane();
scrollPane.setContent(outerGroup);
scrollPane.setOnScroll(new ZoomHandler(innerGroup));
StackPane stackPane = new StackPane();
stackPane.getChildren().add(scrollPane);
Scene scene = SceneBuilder.create()
.width(WINDOW_WIDTH)
.height(WINDOW_HEIGHT)
.root(stackPane)
.build();
stage.setScene(scene);
stage.show();
}
private Group createSixRectangles() {
return new Group(
createRectangle(0, 0), createRectangle(110, 0), createRectangle(220, 0),
createRectangle(0, 110), createRectangle(110, 110), createRectangle(220, 110),
createRectangle(0, 220), createRectangle(110, 220), createRectangle(220, 220)
);
}
private Rectangle createRectangle(int x, int y) {
Rectangle rectangle = new Rectangle(x, y, 100, 100);
rectangle.setStroke(Color.ORANGERED);
rectangle.setFill(Color.ORANGE);
rectangle.setStrokeWidth(3d);
return rectangle;
}
}