JavaFX TextArea 获取 scrollTop 百分比

Question

我有一个可垂直滚动的 TextArea ( wrapTextis true)，我想显示它的滚动百分比。我创建了一个这样的监听器：textArea.scrollTopProperty().addListener(new ChangeListener<Number>() {    @Override    public void changed(ObservableValue<? extends Number> observable, Number oldValue, Number newValue) {        final float percentage = newValue / denominator * 100.0f;        System.out.println("Scroll top: " + percentage);    }});所以看起来我需要检索一些属性才能将其用作denominator. 任何帮助将不胜感激！谢谢。

Answer 1

您需要ScrollBar从TextArea. 访问它的唯一方法是使用以下lookup()方法：

ScrollBar scrollBar = (ScrollBar) textArea.lookup(".scroll-bar:vertical");

请注意，这必须在屏幕上呈现后完成。TextArea

从那里，您可以设置几个绑定到 aLabel以显示当前滚动的百分比：

DoubleProperty scrollPercentage = new SimpleDoubleProperty();

scrollPercentage.bind(Bindings.createDoubleBinding(() -> scrollBar.valueProperty().get() * 100, scrollBar.valueProperty()));

label.textProperty().bind(Bindings.format("%,.2f", scrollPercentage));

这是一个简单的 MCVE 来演示：

import javafx.application.Application;

import javafx.application.Platform;

import javafx.beans.binding.Bindings;

import javafx.beans.property.DoubleProperty;

import javafx.beans.property.SimpleDoubleProperty;

import javafx.geometry.Insets;

import javafx.geometry.Pos;

import javafx.scene.Scene;

import javafx.scene.control.Label;

import javafx.scene.control.ScrollBar;

import javafx.scene.control.TextArea;

import javafx.scene.layout.Priority;

import javafx.scene.layout.VBox;

import javafx.stage.Stage;

public class ScrollBarPercentage extends Application {

    public static void main(String[] args) {

        launch(args);

    }

    @Override

    public void start(Stage primaryStage) {

        // Simple Interface

        VBox root = new VBox(10);

        root.setAlignment(Pos.CENTER);

        root.setPadding(new Insets(10));

        // Simple TextArea

        TextArea textArea = new TextArea() {{

            setWrapText(true);

            setText("Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec suscipit posuere sodales. Mauris sodales velit vel sollicitudin volutpat. Sed rhoncus sodales sagittis. Duis ut congue mauris, sit amet tincidunt lacus. Mauris convallis convallis massa, in cursus nulla sollicitudin et. Etiam quis congue mi, nec tempor tellus. Praesent sed mollis ante. Curabitur fermentum volutpat massa, non dapibus tortor rutrum et. Sed lorem dui, pharetra ac lacus non, ultricies varius enim. Ut nec ante lectus. Vestibulum scelerisque vulputate facilisis. Cras commodo sapien eros, eu pellentesque massa congue vel. Aliquam urna neque, elementum iaculis justo eget, semper ullamcorper magna.\n\n" +

                    "Suspendisse ultricies porta auctor. Praesent ultrices lectus sed maximus ultricies. Nulla pharetra, augue in luctus fringilla, enim turpis auctor turpis, eu ullamcorper metus ligula ac nisl. Quisque accumsan tempus varius. Mauris blandit erat eget enim tempor accumsan. Nam iaculis libero a est sollicitudin, non fermentum ex viverra. Vivamus pharetra neque non augue feugiat efficitur. In hac habitasse platea dictumst. Aliquam tempor enim blandit blandit tempor. Ut porta ex sed congue maximus. Nulla non tortor est. Integer vel placerat lectus, vel tempus justo. Vestibulum ut dui sit amet mauris maximus ultricies vel in quam. Fusce suscipit volutpat magna eget ornare. Donec elementum ultricies tortor, volutpat porta enim fermentum sit amet.\n\n" +

                    "Aenean id erat at metus accumsan sodales. Suspendisse sed nisi iaculis, congue lectus et, efficitur nibh. Curabitur placerat erat et justo blandit porttitor. Nam mollis tempor magna, sed rutrum neque. Nunc mollis nunc posuere ex iaculis elementum. Nunc quam diam, aliquam ut ex mollis, facilisis varius ligula. Donec nec venenatis nunc, et auctor mi.");

        }};

        VBox.setVgrow(textArea, Priority.ALWAYS);

        // Label to display percentage scrolled

        Label label = new Label();

        // Since the lookup will only work after the TextArea has been rendered in the Scene, we need to retrieve it later with the runLater() method

        Platform.runLater(() -> {

            // Get the ScrollBar from the TextArea using a lookup

            ScrollBar scrollBar = (ScrollBar) textArea.lookup(".scroll-bar:vertical");

            // Now create a DoubleProperty that we'll bind to our scroll value * 100

            DoubleProperty scrollPercentage = new SimpleDoubleProperty();

            scrollPercentage.bind(Bindings.createDoubleBinding(() -> scrollBar.valueProperty().get() * 100, scrollBar.valueProperty()));

            // Bind the label to show a formatted percentage of the scrolling

            label.textProperty().bind(Bindings.format("%,.2f", scrollPercentage));

        });

        root.getChildren().addAll(textArea, new Label("Scrolled:"), label);

        // Show the stage

        primaryStage.setScene(new Scene(root));

        primaryStage.setTitle("Sample");

        primaryStage.show();

    }

}

结果：

https://i.stack.imgur.com/ngoR6.png