Share the same code between TextField's actionEvent() and focusedProperty.addListener()

Question

Hello.
Following the DRY principle, I want the same validation piece of code to be executed in the actionEvent() and focusedProperty.addListener() of my TextField. I tried creating a private method and calling it in both handlers, but in the actionEvent handler I'm accessing the event object to play an animation on the textfield, which isn't passed in the changed() method of the listener for the focusedProperty. What's the best way to solve this without repeating code?

Answer 1

Yup, sorry; that's what comes from working off a phone without checking the API docs... It's a ReadOnlyProperty, not a Property.
This works:
import java.util.regex.Pattern;
import javafx.application.Application;
import javafx.beans.property.ReadOnlyProperty;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.TextField;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
public class ValidatingTextFieldExample extends Application {
@Override
  public void start(Stage primaryStage) {
  final VBox root = new VBox(5);
  final ChangeListener<Boolean> focusListener = new ChangeListener<Boolean>() {
            @Override
            public void changed(ObservableValue<? extends Boolean> observable,
                    Boolean oldValue, Boolean newValue) {
                if (! newValue) {
                    TextField textField = (TextField) ((ReadOnlyProperty<?>) observable).getBean();
                     doValidation(textField);
  final EventHandler<ActionEvent> actionHandler = new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {
                TextField textField = (TextField) event.getSource();
                doValidation(textField);
        TextField tf1 = new TextField();
        TextField tf2 = new TextField();
        tf1.setOnAction(actionHandler);
        tf1.focusedProperty().addListener(focusListener);
        tf2.setOnAction(actionHandler);
        tf2.focusedProperty().addListener(focusListener);
        root.getChildren().addAll(tf1, tf2);
        primaryStage.setScene(new Scene(root, 300, 150));
        primaryStage.show();
  private void doValidation(TextField textField) {
      if (isTextValid(textField.getText())) {
          textField.setStyle("");
      } else {
          textField.setStyle("-fx-text-fill: red;");
  private boolean isTextValid(String text) {
      // just digits are valid (very simple example)
      return Pattern.matches("^[0-9]*$", text);
  public static void main(String[] args) {
  launch(args);
But also consider this solution, which doesn't use the events at all, has no downcasting, but still fulfills your DRY principle:
import java.util.regex.Pattern;
import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.TextField;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
public class ValidatingTextFieldExample extends Application {
@Override
  public void start(Stage primaryStage) {
  final VBox root = new VBox(5);
        TextField tf1 = new TextField();
        TextField tf2 = new TextField();
        registerValidationHandlers(tf1);
        registerValidationHandlers(tf2);
        root.getChildren().addAll(tf1, tf2);
        primaryStage.setScene(new Scene(root, 300, 150));
        primaryStage.show();
  private void registerValidationHandlers(final TextField textField) {
      textField.setOnAction(new EventHandler<ActionEvent>() {
          @Override
          public void handle(ActionEvent event) {
              doValidation(textField);
      textField.focusedProperty().addListener(new ChangeListener<Boolean>() {
          @Override
          public void changed(ObservableValue<? extends Boolean> observable, Boolean wasFocused, Boolean isFocused) {
              if (! isFocused) {
                  doValidation(textField);
  private void doValidation(TextField textField) {
      if (isTextValid(textField.getText())) {
          textField.setStyle("");
      } else {
          textField.setStyle("-fx-text-fill: red;");
  private boolean isTextValid(String text) {
      // just digits are valid (very simple example)
      return Pattern.matches("^[0-9]*$", text);
  public static void main(String[] args) {
  launch(args);
You could even make the registerValidationHandlers method a varargs method, which would even avoid replicating the call to that method...