CODEWITHSUNDEEP
javajavafx
stackmonkey
stackmonkey

Reputation: 115

Corralation between TextArea height and Scrollbar scrollTopProperty

I have made a TextArea (JavaFX), and once I fill it up with text a Scrollbar appears... without the need of specialy adding it.

As part of my program I wan to know when the scrollbar is close to the buttom of the TextArea-ScrollPane.

I know that I can get the position of the scrollbar with TextArea.scrollTopProperty(), but comparing that with TextArea.getHeight() just can not be done as the values dont seem to follow any ratio (that I can see).

So can anyone tell me how to figure out when the scrollbar is close to its bottom/start or top/end?

Upvotes: 0

Views: 83

Answers (1)

James_D
James_D

Reputation: 209418

The scrollTopProperty is the amount scrolled vertically, in pixels. The maximum amount this can be is the difference between the size of the viewport, and the size of the actual text being scrolled. You can get these via lookups: the CSS documentation specifies the class names for the scroll pane and its content.

import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.beans.property.DoubleProperty;
import javafx.beans.property.SimpleDoubleProperty;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.TextArea;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;

public class TextAreaScrollMonitor extends Application {

    @Override
    public void start(Stage primaryStage) {
        TextArea textArea = new TextArea();
        textArea.setWrapText(true);

        DoubleProperty percentScrolled = new SimpleDoubleProperty();
        percentScrolled.bind(Bindings.createDoubleBinding(() -> {

            Node text = textArea.lookup(".content");
            Node scrollPane = textArea.lookup(".scroll-pane");

            if (text == null || scrollPane == null) {
                return 0.0 ;
            }

            double textHeight = text.getLayoutBounds().getHeight();
            double textAreaHeight = ((ScrollPane) scrollPane).getViewportBounds().getHeight();

            if (textHeight <= textAreaHeight) {
                return 100.0 ;
            }

            return 100.0 * textArea.getScrollTop() / (textHeight - textAreaHeight) ;

        }, textArea.scrollTopProperty()));

        Label label = new Label();
        label.textProperty().bind(percentScrolled.asString("Percent scrolled: %.1f"));

        textArea.setText("Lorem ipsum dolor sit amet, consectetur adipiscing elit. "
                + "Curabitur ornare tellus et libero dignissim, consectetur sollicitudin ante vulputate. "
                + "Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. "
                + "Integer rhoncus suscipit ligula eget maximus. Sed luctus viverra suscipit. Curabitur ac ligula "
                + "faucibus erat aliquet gravida sit amet a mauris. Cras vestibulum urna lacus, ac congue risus congue sed. "
                + "Duis massa enim, pharetra sit amet tellus vitae, consectetur ullamcorper nunc. "
                + "Integer lobortis porta lectus sed cursus. Suspendisse gravida felis tellus, "
                + "nec sagittis felis cursus eu. Proin dictum ac nisl in aliquet. "
                + "Etiam placerat consectetur placerat. Cras commodo mauris augue, nec tincidunt mauris posuere et. "
                + "Mauris rhoncus ex ac elit ullamcorper, tempor tincidunt odio volutpat.Nullam est odio, blandit in ex id, "
                + "pellentesque rutrum odio. Nullam aliquam sem turpis, eget auctor sapien fermentum sollicitudin. "
                + "Sed ullamcorper, nisi et fermentum tristique, sem urna fermentum massa, vitae tincidunt risus nisi et nisi. "
                + "Aliquam sagittis urna at elit tincidunt, eu lobortis leo vulputate. Vivamus id suscipit lorem. "
                + "Quisque sed nibh nec sem finibus suscipit aliquam eget felis. Suspendisse pulvinar venenatis augue, "
                + "at egestas nibh malesuada sit amet. Vivamus eget egestas velit. Nullam quis placerat elit. "
                + "Morbi aliquam velit nunc, a varius ipsum ultricies quis. Phasellus dui odio, viverra a sapien at, "
                + "auctor iaculis nunc.Praesent mauris nibh, dignissim vitae massa a, dapibus rutrum enim. "
                + "Aliquam aliquam tincidunt erat nec posuere. Ut elementum vel velit quis interdum. "
                + "Proin eget dapibus sapien. Cras faucibus urna nulla, sed volutpat ligula efficitur nec. "
                + "Aenean non ullamcorper nulla. Curabitur quis arcu sit amet nunc lacinia consectetur vitae nec elit. "
                + "In quis mollis dui. Morbi consectetur condimentum erat. Curabitur ut mollis dui. "
                + "Proin molestie gravida tempus.Nam consequat interdum odio at condimentum. Vestibulum augue tellus, "
                + "dignissim ac sem et, iaculis cursus massa. Donec facilisis nunc at erat malesuada, in luctus felis dictum. "
                + "Vivamus scelerisque accumsan tellus, eget gravida mauris. Etiam eu elit auctor nisl efficitur pretium. "
                + "Duis non eros arcu. Pellentesque tempus nibh et lorem ornare, at placerat sapien placerat. "
                + "Ut iaculis lectus at libero condimentum blandit. Vestibulum euismod dolor ut egestas laoreet. "
                + "Phasellus tempus at enim at posuere. Donec erat eros, mattis et justo fringilla, laoreet interdum tellus."
                + "In vehicula hendrerit nulla, sed ultrices neque rhoncus a. Proin vel volutpat lectus. "
                + "Sed egestas tellus ac consectetur elementum. Donec dolor ipsum, auctor eu turpis feugiat, "
                + "ullamcorper efficitur quam. Cras efficitur libero pulvinar magna tincidunt, eget faucibus libero suscipit. "
                + "Fusce elementum nulla vel magna porttitor elementum. Quisque accumsan euismod porttitor. "
                + "Sed nec sem non nisi aliquam consequat sit amet et metus. Curabitur facilisis enim non tristique tristique. "
                + "Morbi purus libero, molestie non purus ut, commodo semper dui. Quisque tellus nunc, porttitor ac egestas id, "
                + "venenatis vitae felis. Curabitur convallis dui lectus, eu sodales leo laoreet nec. Integer interdum pharetra dolor, "
                + "vitae sodales augue cursus sit amet.Aliquam ut turpis accumsan, lacinia felis eu, tristique eros. "
                + "Nullam laoreet eros tortor, et egestas augue sagittis nec. "
                + "Nam sit amet odio non eros maximus interdum sit amet et dolor. Nunc blandit tincidunt.");


        Scene scene = new Scene(new BorderPane(textArea, label, null, null, null));
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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

Upvotes: 1

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