如何滚动以使滚动窗格内容中的节点可见？

Question

给定一个带有一些子节点的巨大的AnchorPane是ScrollPane的内容，我如何滚动以使当前视口之外的子节点之一可见？

Answer 1

为了获得一个完美的快照，您需要考虑滚动条的开始和停止位置。视口从0开始的半视口（边界scollpane）开始，从最大边界停止半视口。边界与视口图片

so：半视口下的节点Y-

在这两者之间，我们需要计算总高度-1视口（一半开始，一半结束）和节点y-一半视口。然后（节点y-半视口）/（总高度-1视口）

                double heightViewPort = scrollPane.getViewportBounds().getHeight();
                double heightScrollPane = scrollPane.getContent().getBoundsInLocal().getHeight();
                double y = Label.getBoundsInParent().getMaxY();
                if (y<(heightViewPort/2)){
                    scrollPane.setVvalue(0);
                    // below 0 of scrollpane

                }else if ((y>=(heightViewPort/2))&(y<=(heightScrollPane-heightViewPort/2))){
                   // between 0 and 1 of scrollpane
                    scrollPane.setVvalue((y-(heightViewPort/2))/(heightScrollPane-heightViewPort));
                }
                else if(y>= (heightScrollPane-(heightViewPort/2))){
                    // above 1 of scrollpane
                    scrollPane.setVvalue(1);

                }

Answer 2

我为这个案例创建了一个稍微优雅一点的版本。但是，我只能在y轴上进行测试。希望能有帮助

private static void ensureVisible(ScrollPane scrollPane, Node node) {
    Bounds viewport = scrollPane.getViewportBounds();
    double contentHeight = scrollPane.getContent().localToScene(scrollPane.getContent().getBoundsInLocal()).getHeight();
    double nodeMinY = node.localToScene(node.getBoundsInLocal()).getMinY();
    double nodeMaxY = node.localToScene(node.getBoundsInLocal()).getMaxY();

    double vValueDelta = 0;
    double vValueCurrent = scrollPane.getVvalue();

    if (nodeMaxY < 0) {
        // currently located above (remember, top left is (0,0))
        vValueDelta = (nodeMinY - viewport.getHeight()) / contentHeight;
    } else if (nodeMinY > viewport.getHeight()) {
        // currently located below
        vValueDelta = (nodeMinY + viewport.getHeight()) / contentHeight;
    }
    scrollPane.setVvalue(vValueCurrent + vValueDelta);
}

Answer 3

编辑：下一个示例中的代码比我的更精确：https://stackoverflow.com/a/23518314/1054140

您需要在content中找到此内部节点的坐标，并相应地调整滚动窗格的vValue和hValue。

请参阅下一个小应用程序中的ensurevicible（）方法：

public class ScrollPaneEnsureVisible extends Application {

    private static final Random random = new Random();

    private static void ensureVisible(ScrollPane pane, Node node) {
        double width = pane.getContent().getBoundsInLocal().getWidth();
        double height = pane.getContent().getBoundsInLocal().getHeight();

        double x = node.getBoundsInParent().getMaxX();
        double y = node.getBoundsInParent().getMaxY();

        // scrolling values range from 0 to 1
        pane.setVvalue(y/height);
        pane.setHvalue(x/width);

        // just for usability
        node.requestFocus();
    }

    @Override
    public void start(Stage primaryStage) {

        final ScrollPane root = new ScrollPane();
        final Pane content = new Pane();
        root.setContent(content);

        // put 10 buttons at random places with same handler
        final EventHandler<ActionEvent> handler = new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {
                int index = random.nextInt(10);
                System.out.println("Moving to button " + index);
                ensureVisible(root, content.getChildren().get(index));
            }
        };

        for (int i = 0; i < 10; i++) {
            Button btn = new Button("next " + i);
            btn.setOnAction(handler);
            content.getChildren().add(btn);
            btn.relocate(2000 * random.nextDouble(), 2000 * random.nextDouble());
        }

        Scene scene = new Scene(root, 300, 250);
        primaryStage.setScene(scene);
        primaryStage.show();

        // run once to don't search for a first button manually
        handler.handle(null);
    }

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