How to trigger the ChangeListener when TextField loses focus ? JAVAFX

Question

I have multiple TextFields and i'm trying to find the sum of the numbers entered into them by the user.

 credit1.textProperty().addListener(new creditChangeListener(this.credit1, this.course1, this.grade1));
 credit2.textProperty().addListener(new creditChangeListener(this.credit2, this.course2, this.grade2));
 credit3.textProperty().addListener(new creditChangeListener(this.credit3, this.course3, this.grade3));
 credit4.textProperty().addListener(new creditChangeListener(this.credit4, this.course4, this.grade4));

I have an inner class implementing ChangeListener to handle user input for each TextField.

 private class creditChangeListener implements ChangeListener<String>{

    private final TextField credit;
    private final TextField course;
    private final TextField grade;

    public creditChangeListener(TextField credit, TextField course, TextField grade){
        this.credit = credit;
        this.course = course;
        this.grade = grade;
    }

    @Override
    public void changed(ObservableValue<? extends String> observable, String oldValue, String newValue){
        if(!credit.getText().matches("[0-9]+")) grade.setText("");
        if(!course.getText().isEmpty() && !grade.getText().isEmpty()) {
            addSum();
        }
    }

    private void addSum(){
        sum += Integer.parseInt(credit.getText());
        System.out.println("Current sum: " + sum);
    }
}

I need to find the sum of the numbers entered into those credit TextFields, however the ChangeListener adds digit by digit while i need the whole number entered. I thought of triggering the ChangeListener after the TextFields lose focus, but i couldn't find out how to achieve that nor am I sure that it is the proper way of doing it.

This might help you: [Event when window/stage lost focus](https://stackoverflow.com/questions/24038988/event-when-window-stage-lost-focus) — Austin Schaefer, Aug 01 '17 at 11:18
At which point do you want to perform the computation of the sum? How should the program know when the user finished entering text? — user1803551, Aug 01 '17 at 12:27

Rafael Guillen · Accepted Answer · 2017-08-01T14:24:48.887

I had the same problem some time ago, I solved it adding a Listener to the Focused property instead the Changed property. First create a Listener you can reuse:

private ChangeListener<Boolean> focusListener = new ChangeListener<Boolean>() {
    @Override
    public void changed(ObservableValue<? extends Boolean> observable, Boolean oldValue, Boolean newValue) {
        if (!newValue) {
            sum(); //Do the sum logic here!!!
        }
    }
};

Then apply the change listener to all your textfields

credit1.focusedProperty().addListener(focusListener);
credit2.focusedProperty().addListener(focusListener);
credit3.focusedProperty().addListener(focusListener);
credit4.focusedProperty().addListener(focusListener);

You can implement your inner class this way to trigger the event every time a Textfield loses focus.

Hope it helps...

How to trigger the ChangeListener when TextField loses focus ? JAVAFX

1 Answers1