Home » Java » Desktop Java » JavaFX Tip 30: ScrollPane with DropShadow

About Dirk Lemmermann

JavaFX Tip 30: ScrollPane with DropShadow

In one of my projects I recently noticed that it was hard for the user to see whether the content of a ScrollPane instance was currently scrolled or not. One way of making this more clear is to add a drop shadow to the top of the scroll pane.

This is also something suggested by Google’s Material Design. So I gave it a try. In my solution I simply added a region to the ScrollPane and when laying it out I am moving it out of the viewport bounds of the ScrollPane so that only the shadow effect applied to the region still reaches into it.

To really make sure that the region is not visible I also had to set a clip on the ScrollPane. This works quite well although I must admit I am not 100% sure this is the best way to do it. So if anybody has any suggestions / alternative approaches then please leave a comment.

Below you see before and after scrolling screenshots of one of the screens of our application.

Before Scrolling

ScrollPane before scroll

After Scrolling

ScrollPane with dropshadow

BTW: I implemented this in such a way that the drop shadow doesn’t just appear all of a sudden, but it moves into the viewport step by step, depending on how far the user has scrolled. To see this you need to scroll down very slowly.

The code for the ShadowScrollPane can be found in this gist on GitHub:

package uk.co.senapt.desktop.shell;

import javafx.beans.property.BooleanProperty;
import javafx.beans.property.SimpleBooleanProperty;
import javafx.geometry.Insets;
import javafx.scene.Node;
import javafx.scene.control.ScrollPane;
import javafx.scene.layout.Region;
import javafx.scene.shape.Rectangle;

/**
 * Created by lemmi on 23.08.17.
 */
public class ShadowScrollPane extends ScrollPane {

    private Region shadow = new Region();

    public ShadowScrollPane() {
        super();

        init();
    }

    public ShadowScrollPane(Node content) {
        super(content);
        init();
    }

    private void init() {
        skinProperty().addListener(it -> {
            getChildren().addAll(shadow);
        });

        setFitToWidth(true);
        setVbarPolicy(ScrollBarPolicy.NEVER);
        setHbarPolicy(ScrollBarPolicy.NEVER);

        shadow.setManaged(false);
        shadow.setStyle("-fx-pref-height: 10;" +
                "-fx-background-color: black;" +
                "-fx-effect: dropshadow(gaussian, rgba(0, 0, 0, .75), 20, 0.19, 0, 6);");
        shadow.getStyleClass().add("shadow");
        shadow.visibleProperty().bind(showShadowProperty());
        shadow.setMouseTransparent(true);
        shadow.visibleProperty().bind(vvalueProperty().greaterThan(0));

        Rectangle clip = new Rectangle();
        clip.widthProperty().bind(widthProperty());
        clip.heightProperty().bind(heightProperty());
        setClip(clip);

        vvalueProperty().addListener(it -> {
            if (lastOffset != computeOffset()) {
                requestLayout();
            }
        });
        showShadowProperty().addListener(it -> requestLayout());
    }

    private final BooleanProperty showShadow = new SimpleBooleanProperty(this, "showShadow", true);

    public final BooleanProperty showShadowProperty() {
        return showShadow;
    }

    public final boolean isShowShadow() {
        return showShadow.get();
    }

    public final void setShowShadow(boolean show) {
        showShadow.set(show);
    }

    private final int SHADOW_HEIGHT = 30;

    @Override
    protected void layoutChildren() {
        super.layoutChildren();

        if (isShowShadow()) {
            Insets insets = getInsets();
            double w = getWidth();
            double offset = computeOffset();
            shadow.resizeRelocate(-10, insets.getTop() - shadow.prefHeight(-1) - SHADOW_HEIGHT + offset, w + 20, shadow.prefHeight(-1) - 1);
            lastOffset = offset;
        }
    }

    private double lastOffset = 0;

    private double computeOffset() {
        if (getContent() != null) {
            return Math.min(getVvalue() * getContent().prefHeight(-1), SHADOW_HEIGHT);
        }

        return 0;
    }
}
Published on Java Code Geeks with permission by Dirk Lemmermann, partner at our JCG program. See the original article here: JavaFX Tip 30: ScrollPane with DropShadow

Opinions expressed by Java Code Geeks contributors are their own.

Do you want to know how to develop your skillset to become a Java Rockstar?

Subscribe to our newsletter to start Rocking right now!

To get you started we give you our best selling eBooks for FREE!

 

1. JPA Mini Book

2. JVM Troubleshooting Guide

3. JUnit Tutorial for Unit Testing

4. Java Annotations Tutorial

5. Java Interview Questions

6. Spring Interview Questions

7. Android UI Design

 

and many more ....

 

Receive Java & Developer job alerts in your Area

I have read and agree to the terms & conditions

 

Subscribe
Notify of
guest

This site uses Akismet to reduce spam. Learn how your comment data is processed.

0 Comments
Inline Feedbacks
View all comments