What is the recommended way to make a numeric Text

Question

I need to restrict input into a TextField to integers. Any advice?

Answer 1

This is what I use:

private TextField textField;
textField.textProperty().addListener(new ChangeListener<String>() {
    @Override
    public void changed(ObservableValue<? extends String> observable, String oldValue, String newValue) {
        if(!newValue.matches("[0-9]*")){
            textField.setText(oldValue);
        }

    }
});

The same in lambda notation would be:

private TextField textField;
textField.textProperty().addListener((observable, oldValue, newValue) -> {
    if(!newValue.matches("[0-9]*")){
        textField.setText(oldValue);
    }
});

Answer 2

I would like to improve Evan Knowles answer: https://stackoverflow.com/a/30796829/2628125

In my case I had class with handlers for UI Component part. Initialization:

this.dataText.textProperty().addListener((observable, oldValue, newValue) -> this.numericSanitization(observable, oldValue, newValue));

And the numbericSanitization method:

private synchronized void numericSanitization(ObservableValue<? extends String> observable, String oldValue, String newValue) {
    final String allowedPattern = "\\d*";

    if (!newValue.matches(allowedPattern)) {
        this.dataText.setText(oldValue);
    }
}

Keyword synchronized is added to prevent possible render lock issue in javafx if setText will be called before old one is finished execution. It is easy to reproduce if you will start typing wrong chars really fast.

Another advantage is that you keep only one pattern to match and just do rollback. It is better because you can easily abstragate solution for different sanitization patterns.

Answer 3

The TextInput has a TextFormatter which can be used to format, convert and limit the types of text that can be input.

The TextFormatter has a filter which can be used to reject input. We need to set this to reject anything that's not a valid integer. It also has a converter which we need to set to convert the string value to an integer value which we can bind later on.

Lets create a reusable filter:

public class IntegerFilter implements UnaryOperator<TextFormatter.Change> {
    private final static Pattern DIGIT_PATTERN = Pattern.compile("\\d*");

    @Override
    public Change apply(TextFormatter.Change aT) {
        return DIGIT_PATTERN.matcher(aT.getText()).matches() ? aT : null;
    }
}

The filter can do one of three things, it can return the change unmodified to accept it as it is, it can alter the change in some way it deems fit or it can return null to reject the change all together.

We will use the standard IntegerStringConverter as a converter.

Putting it all together we have:

TextField textField = ...;

TextFormatter<Integer> formatter = new TextFormatter<>(
    new IntegerStringConverter(), // Standard converter form JavaFX
    defaultValue, 
    new IntegerFilter());
formatter.valueProperty().bindBidirectional(myIntegerProperty);

textField.setTextFormatter(formatter);

If you want don't need a reusable filter you can do this fancy one-liner instead:

TextFormatter<Integer> formatter = new TextFormatter<>(
    new IntegerStringConverter(), 
    defaultValue,  
    c -> Pattern.matches("\\d*", c.getText()) ? c : null );

Answer 4

    rate_text.textProperty().addListener(new ChangeListener<String>() {

        @Override
        public void changed(ObservableValue<? extends String> observable,
                String oldValue, String newValue) {
            String s="";
            for(char c : newValue.toCharArray()){
                if(((int)c >= 48 && (int)c <= 57 || (int)c == 46)){
                    s+=c;
                }
            }
            rate_text.setText(s);
        }
    });

This works fine as it allows you to enter only integer value and decimal value (having ASCII code 46).