Cfrgtkky

I am trying to track input to TextField and allow user to input only 1 symbol per TextField, here is my code:

package sample;



import javafx.application.Application;

import javafx.scene.Parent;

import javafx.scene.Scene;

import javafx.scene.control.TextField;

import javafx.scene.layout.Pane;

import javafx.stage.Stage;



public class Main extends Application {



    @Override

    public void start(Stage primaryStage) throws Exception{

        TextField textField = new TextField(); //creating new textfield

        Pane window = new Pane();

        Parent root = window;

        window.getChildren().addAll(textField); //adding textfield to the window

        primaryStage.setScene(new Scene(root, 200, 50));

        primaryStage.show();

        textField.textProperty().addListener(event ->

             {

                 try {

                     if (textField.getLength() > 1) { //check if the length of the textfield text exceeds 1

                         System.out.println("NOT Accepted");

                         textField.setText(String.valueOf(textField.getText().charAt(0))); //set textfield text to first char only

                     } else {

                         System.out.println("Accepted");

                     }

                 } catch (IndexOutOfBoundsException Bound) {}

             }

             );

        }



    public static void main(String args) {

        launch(args);

    }

}

When I press any symbol first time, everything works good, but when I press second time, event listener repeats 3 times. Here the exapmle:
"a" key has been pressed, console output:

Accepted  //<---Correct

"a" key (or any another key) has been pressed second time, console output:

NOT Accepted  //<---Correct

Accepted      //<---Not correct

Accepted      //<---Not correct

As shown above listener repeats 3 times.
But I expect that console should show only "NOT Accepted" and shouldn't repeat 2 times more.

Instead of using a ChangeListener, I recommend a simple TextFormatter instead. This allows you to prevent the change without triggering another event.

    textField.setTextFormatter(new TextFormatter<String>((TextFormatter.Change change) -> {

        String newText = change.getControlNewText();

        if (newText.length() == 1) {

            System.out.println("Accepted");

        } else if (newText.length() > 1) {

            System.out.println("NOT Accepted");

            return null;

        }



        return change;

    }));