Automatic scrolling feature in JavaFX

Question

Automatic scrolling feature in JavaFX

I am currently working on developing a chat box using JavaFX. My goal is to implement an auto-scroll feature that will scroll down the page when it gets filled up. However, I am facing some issues with this functionality.

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.TextField;
import javafx.scene.input.KeyCode;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Priority;
import javafx.scene.layout.VBox;
import javafx.scene.text.Text;
import javafx.scene.text.TextFlow;
import javafx.stage.Stage;

public class ChatBox extends Application{
final ScrollPane sp = new ScrollPane();
public static void main(String[] args){
launch(args);
}
public void start(Stage stage){
TextFlow textFlow = new TextFlow();
textFlow.setPadding(new Insets(10));
textFlow.setLineSpacing(10);
textFlow.setPrefSize(300,300);
TextField textField = new TextField();
textField.setPrefSize(50,30);
Button button = new Button("Send");
button.setPrefSize(80,30);
VBox container = new VBox();
VBox box = new VBox();
box.getChildren().addAll(sp,textFlow);
container.setPadding(new Insets(10));
container.getChildren().addAll(box, new HBox(textField, button));
VBox.setVgrow(sp, Priority.ALWAYS);
VBox.setVgrow(textFlow, Priority.ALWAYS);
textField.prefWidthProperty().bind(container.widthProperty().subtract(button.prefWidthProperty()));

// On Enter press
textField.setOnKeyPressed(e -> {
    if(e.getCode() == KeyCode.ENTER) {
        button.fire();
    }
});

button.setOnAction(e -> {
    Text message;
    if(textFlow.getChildren().size()==0){
        message = new Text(textField.getText());
    } else {
        // Add new line if not the first child
        message = new Text("\n" + textField.getText());
    }
    textFlow.getChildren().add(message);
    textField.clear();
    textField.requestFocus();
});
VBox vb = new VBox();
vb.getChildren().addAll(textFlow);
sp.setVmax(440);
sp.setPrefSize(400, 300);
sp.setContent(vb);
sp.vvalueProperty().bind((ObservableValue<? extends Number>) vb.heightProperty());
//sp.setPannable(true);
Scene scene = new Scene(container, 400, 300);
stage.setScene(scene);
stage.setTitle("ChatBox");
stage.show();
}
}

After running the code, I observed that the page scrolls down automatically even though it should have remained at the top. Additionally, the text "hi" moves upwards despite being the first message. The scrollbar indicates a position below where it should be located. Can anyone provide guidance on how to address this issue?

java css user-interface javafx scrollbar

Answer 1

Answer №1

Make sure to set the preferred size for Text Flow in order to avoid unnecessary scrolling, as it needs to adjust its size while being inside a scroll pane. Here's an example:

package com.grs.stackOverFlow.pack161124;

import javafx.application.Application;
import javafx.beans.value.ObservableValue;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.TextField;
import javafx.scene.input.KeyCode;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Priority;
import javafx.scene.layout.VBox;
import javafx.scene.text.Text;
import javafx.scene.text.TextFlow;
import javafx.stage.Stage;

public class ChatBox extends Application{
    final ScrollPane sp = new ScrollPane();
    public static void main(String[] args){
        launch(args);
    }
    public void start(Stage stage){
        TextFlow textFlow = new TextFlow();
        //textFlow.setPadding(new Insets(10));
        textFlow.setLineSpacing(10);
        //textFlow.setPrefSize(300,300);
        TextField textField = new TextField();
        textField.setPrefSize(50,30);
        Button button = new Button("Send");
        button.setPrefSize(80,30);
        VBox container = new VBox();
        VBox box = new VBox();
        box.getChildren().addAll(sp,textFlow);
        container.setPadding(new Insets(10));
        container.getChildren().addAll(box, new HBox(textField, button));
        VBox.setVgrow(sp, Priority.ALWAYS);
        VBox.setVgrow(textFlow, Priority.ALWAYS);
        textField.prefWidthProperty().bind(container.widthProperty().subtract(button.prefWidthProperty()));

        // On Enter press
        textField.setOnKeyPressed(e -> {
            if(e.getCode() == KeyCode.ENTER) {
                button.fire();
            }
        });

        button.setOnAction(e -> {
            Text text;
            if(textFlow.getChildren().size()==0){
                text = new Text(textField.getText());
            } else {
                // Add new line if not the first child
                text = new Text("\n" + textField.getText());
            }
            textFlow.getChildren().add(text);
            textField.clear();
            textField.requestFocus();
        });
        VBox vb = new VBox();
        vb.getChildren().addAll(textFlow);
        sp.setVmax(440);
        sp.setPrefSize(400, 300);
        sp.setContent(vb);
        sp.vvalueProperty().bind((ObservableValue<? extends Number>) vb.heightProperty());
        //sp.setPannable(true);
        Scene scene = new Scene(container, 400, 300);
        stage.setScene(scene);
        stage.setTitle("ChatBox");
        stage.show();
    }
}

[![enter image description here][1]][1]

Answer 2

Make sure to set the preferred size for Text Flow in order to avoid unnecessary scrolling, as it needs to adjust its size while being inside a scroll pane. Here's an example:

package com.grs.stackOverFlow.pack161124;

import javafx.application.Application;
import javafx.beans.value.ObservableValue;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.TextField;
import javafx.scene.input.KeyCode;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Priority;
import javafx.scene.layout.VBox;
import javafx.scene.text.Text;
import javafx.scene.text.TextFlow;
import javafx.stage.Stage;

public class ChatBox extends Application{
    final ScrollPane sp = new ScrollPane();
    public static void main(String[] args){
        launch(args);
    }
    public void start(Stage stage){
        TextFlow textFlow = new TextFlow();
        //textFlow.setPadding(new Insets(10));
        textFlow.setLineSpacing(10);
        //textFlow.setPrefSize(300,300);
        TextField textField = new TextField();
        textField.setPrefSize(50,30);
        Button button = new Button("Send");
        button.setPrefSize(80,30);
        VBox container = new VBox();
        VBox box = new VBox();
        box.getChildren().addAll(sp,textFlow);
        container.setPadding(new Insets(10));
        container.getChildren().addAll(box, new HBox(textField, button));
        VBox.setVgrow(sp, Priority.ALWAYS);
        VBox.setVgrow(textFlow, Priority.ALWAYS);
        textField.prefWidthProperty().bind(container.widthProperty().subtract(button.prefWidthProperty()));

        // On Enter press
        textField.setOnKeyPressed(e -> {
            if(e.getCode() == KeyCode.ENTER) {
                button.fire();
            }
        });

        button.setOnAction(e -> {
            Text text;
            if(textFlow.getChildren().size()==0){
                text = new Text(textField.getText());
            } else {
                // Add new line if not the first child
                text = new Text("\n" + textField.getText());
            }
            textFlow.getChildren().add(text);
            textField.clear();
            textField.requestFocus();
        });
        VBox vb = new VBox();
        vb.getChildren().addAll(textFlow);
        sp.setVmax(440);
        sp.setPrefSize(400, 300);
        sp.setContent(vb);
        sp.vvalueProperty().bind((ObservableValue<? extends Number>) vb.heightProperty());
        //sp.setPannable(true);
        Scene scene = new Scene(container, 400, 300);
        stage.setScene(scene);
        stage.setTitle("ChatBox");
        stage.show();
    }
}

[![enter image description here][1]][1]

Answer 3

Answer №2

For this scenario, I suggest opting for a ListView instead of a TextFlow. Using a ListView simplifies the code by handling line breaks and offering a scrollTo method to specify a message index for scrolling:

public void start(Stage stage) {
    TextField textField = new TextField();
    textField.setPrefSize(50, 30);

    Button button = new Button("Send");
    button.setPrefSize(80, 30);

    VBox container = new VBox();

    ListView<String> listView = new ListView();
    listView.setFocusTraversable(false);
    listView.setCellFactory(lv -> new ListCell<String>() {

        private final Text text;

        {
            text = new Text();
            setContentDisplay(ContentDisplay.GRAPHIC_ONLY);
            setGraphic(text);

            // bind wrapping width to available size
            text.wrappingWidthProperty().bind(Bindings.createDoubleBinding(() -> {
                Insets padding = getPadding();
                return getWidth() - padding.getLeft() - padding.getRight();
            }, widthProperty(), paddingProperty()));

        }

        @Override
        protected void updateItem(String item, boolean empty) {
            super.updateItem(item, empty);
            if (empty) {
                text.setText(null);
            } else {
                text.setText(item);
            }
        }

    });

    container.setPadding(new Insets(10));
    container.getChildren().addAll(listView, new HBox(textField, button));
    VBox.setVgrow(listView, Priority.ALWAYS);

    HBox.setHgrow(textField, Priority.ALWAYS);
    HBox.setHgrow(button, Priority.NEVER);

    EventHandler<ActionEvent> handler = e -> {
        // add new message
        listView.getItems().add(textField.getText());

        textField.clear();
        textField.requestFocus();

        // scroll to newly added item
        listView.scrollTo(listView.getItems().size()-1);
    };

    textField.setOnAction(handler);
    button.setOnAction(handler);

    Scene scene = new Scene(container, 400, 300);
    stage.setScene(scene);
    stage.setTitle("ChatBox");
    stage.show();
}

Answer 4

For this scenario, I suggest opting for a ListView instead of a TextFlow. Using a ListView simplifies the code by handling line breaks and offering a scrollTo method to specify a message index for scrolling:

public void start(Stage stage) {
    TextField textField = new TextField();
    textField.setPrefSize(50, 30);

    Button button = new Button("Send");
    button.setPrefSize(80, 30);

    VBox container = new VBox();

    ListView<String> listView = new ListView();
    listView.setFocusTraversable(false);
    listView.setCellFactory(lv -> new ListCell<String>() {

        private final Text text;

        {
            text = new Text();
            setContentDisplay(ContentDisplay.GRAPHIC_ONLY);
            setGraphic(text);

            // bind wrapping width to available size
            text.wrappingWidthProperty().bind(Bindings.createDoubleBinding(() -> {
                Insets padding = getPadding();
                return getWidth() - padding.getLeft() - padding.getRight();
            }, widthProperty(), paddingProperty()));

        }

        @Override
        protected void updateItem(String item, boolean empty) {
            super.updateItem(item, empty);
            if (empty) {
                text.setText(null);
            } else {
                text.setText(item);
            }
        }

    });

    container.setPadding(new Insets(10));
    container.getChildren().addAll(listView, new HBox(textField, button));
    VBox.setVgrow(listView, Priority.ALWAYS);

    HBox.setHgrow(textField, Priority.ALWAYS);
    HBox.setHgrow(button, Priority.NEVER);

    EventHandler<ActionEvent> handler = e -> {
        // add new message
        listView.getItems().add(textField.getText());

        textField.clear();
        textField.requestFocus();

        // scroll to newly added item
        listView.scrollTo(listView.getItems().size()-1);
    };

    textField.setOnAction(handler);
    button.setOnAction(handler);

    Scene scene = new Scene(container, 400, 300);
    stage.setScene(scene);
    stage.setTitle("ChatBox");
    stage.show();
}

Automatic scrolling feature in JavaFX

Answer №1

Answer №2

Similar questions

What is the trick to getting the <label> and <input> elements to show up side by side in an HTML form?

Click anywhere outside the sidemenu to close it

What is the best way to ensure that my cards maintain consistent proportions?

Unusual Behavior of CSS and JQuery Selectors

What is the best way to activate multiple events within an overlapping area containing multiple divs at the same

The iPad screen displays the image in a rotated position while it remains

Bringing JSON information into Java without the need for escape characters

`How to Customize Page Titles and Add Content in WooCommerce`

Efficient PHP caching solution for optimizing JavaScript and CSS performance

Troubleshooting display problems with the categories menu in Opencart version 1.5.1 caused by IE

jQuery Refuses to Perform Animation

What is the best way to position a search icon on the right side using CSS?

The AJAX response consistently returns a 405 status code

What is the best way to achieve full width for text on large screens in Bootstrap 3 while eliminating right margins?

Find the current location of the scroll bar on the view port

Update the div element without needing to reload the entire page

Place a Three.js scene within a jQuery modal dialogue box

Tips for choosing a dropdown option and clicking on specific values in a dropdown menu using Selenium WebDriver with Java programming

Fonts appear altered on a Windows computer

The width specified for the table is not being applied