如何访问ScrollPane的Scrollbars

时间:2012-10-01 17:48:17

标签: java javafx javafx-8 javafx-2

我正在尝试获取有关ScrollBar标准中包含的ScrollPane组件的一些信息。特别是我有兴趣阅读水平height的{​​{1}}。我怎么能参考呢?

3 个答案:

答案 0 :(得分:8)

我认为您可以使用Node类的lookupAll()方法来查找滚动条。 http://docs.oracle.com/javafx/2/api/javafx/scene/Node.html#lookupAll(java.lang.String)

例如:

package com.test;

import java.util.Set;
import javafx.application.Application;
import javafx.geometry.Orientation;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.ScrollBar;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.ScrollPaneBuilder;
import javafx.scene.text.Text;
import javafx.scene.text.TextBuilder;
import javafx.stage.Stage;

public class JavaFxScrollPaneTest extends Application {

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

    @Override
    public void start(Stage primaryStage) {
        String longString = "The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog.";
        Text longText = TextBuilder.create().text(longString).build();

        ScrollPane scrollPane = ScrollPaneBuilder.create().content(longText).build();
        primaryStage.setScene(new Scene(scrollPane, 400, 100));
        primaryStage.show();

        Set<Node> nodes = scrollPane.lookupAll(".scroll-bar");
        for (final Node node : nodes) {
            if (node instanceof ScrollBar) {
                ScrollBar sb = (ScrollBar) node;
                if (sb.getOrientation() == Orientation.HORIZONTAL) {
                    System.out.println("horizontal scrollbar visible = " + sb.isVisible());
                    System.out.println("width = " + sb.getWidth());
                    System.out.println("height = " + sb.getHeight());
                }
            }
        }
    }
}

答案 1 :(得分:5)

这不是最好的做法,但有效,

private boolean determineVerticalSBVisible(final ScrollPane scrollPane) {
    try {
        final ScrollPaneSkin skin = (ScrollPaneSkin) scrollPane.getSkin();
        final Field field = skin.getClass().getDeclaredField("vsb");
        field.setAccessible(true);
        final ScrollBar scrollBar = (ScrollBar) field.get(skin);
        field.setAccessible(false);
        return scrollBar.isVisible();
    } catch (final Exception e) {
        e.printStackTrace();
    }
    return false;
}

将“hsa”用于Horizo​​ntal ScrollBar。

最诚挚的问候, Henrique Guedes。

答案 2 :(得分:3)

由于上述方法并不适合所有人(包括我),因此我对其进行了更多调查,并找到了问题的根源。

通常,这两种方法都可以使用,但是仅在设置了ScrollPaneskin属性后才起作用。就我而言,skin在使用FXMLLoader加载视图后仍然是null

在未初始化skin属性的情况下,通过延迟呼叫(使用单次侦听器)解决了该问题。

工作样板代码:

ScrollPane scrollPane;
// ...
if (scrollPane.getSkin() == null) {
    // Skin is not yet attached, wait until skin is attached to access the scroll bars
    ChangeListener<Skin<?>> skinChangeListener = new ChangeListener<Skin<?>>() {
        @Override
        public void changed(ObservableValue<? extends Skin<?>> observable, Skin<?> oldValue, Skin<?> newValue) {
            scrollPane.skinProperty().removeListener(this);
            accessScrollBar(scrollPane);
        }
    };
    scrollPane.skinProperty().addListener(skinChangeListener);
} else {
    // Skin is already attached, just access the scroll bars
    accessScrollBar(scrollPane);
}

private void accessScrollBar(ScrollPane scrollPane) {
    for (Node node : scrollPane.lookupAll(".scroll-bar")) {
        if (node instanceof ScrollBar) {
            ScrollBar scrollBar = (ScrollBar) node;
            if (scrollBar.getOrientation() == Orientation.HORIZONTAL) {
                // Do something with the horizontal scroll bar

                // Example 1: Print scrollbar height
                // System.out.println(scrollBar.heightProperty().get());

                // Example 2: Listen to visibility changes
                // scrollBar.visibleProperty().addListener((observable, oldValue, newValue) -> {
                //     if(newValue) {
                //         // Do something when scrollbar gets visible
                //     } else {
                //         // Do something when scrollbar gets hidden
                //     }
                // });
            }
            if (scrollBar.getOrientation() == Orientation.VERTICAL) {
                // Do something with the vertical scroll bar
            }

        }
    }
}