Delete first Line of a JavaFx Textarea

Question

Hello I want to delete the first line of a JavaFx textarea. I set a TextFormatter on my Textarea and i want to delete the first line, when more then 20 lines are in it:

private <T> TextFormatter<T> createTextFormatter() {

    final IntegerProperty lines = new SimpleIntegerProperty(1);


    return new TextFormatter<>(change -> {
        if (change.isAdded()) {
            if (change.getText().indexOf('\n') > -1) {
                lines.set(lines.get() + 1);
            }
            if (lines.get() > 20) {
                //TODO
                //delete first row
            }
        }
        return change;
    });
}

II would be glad if someone could help

Thanks

Answer 1

overriding TextArea's replaceText method and a check for line count than delete first line if it exeeds 20 lines seems working,

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.TextArea;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class FixedLineCountTextAreaTry extends Application {
    public static void main(String[] args) {
        launch(args);
    }
    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("Try to enter me more than 20 lines...");
        TextArea ta = new TextArea() {
            @Override
            public void replaceText(int start, int end, String text) {
                super.replaceText(start, end, text);
                while(getText().split("\n", -1).length > 20) {
                    int fle = getText().indexOf("\n");
                    super.replaceText(0, fle+1, "");
                }
                positionCaret(getText().length());
            }
        };

        StackPane root = new StackPane();
        root.getChildren().add(ta);
        primaryStage.setScene(new Scene(root, 300, 500));
        primaryStage.show();
    }
}