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

Mmmm. I ran into that problem weeks ago. As the API doesn't provide a control to achieve that,
you may want to use your own one. I used something like:

public class IntegerBox extends TextBox {
    public-init var value : Integer = 0;
    protected function apply() {
        try {
            value = Integer.parseInt(text);
        } catch (e : NumberFormatException) {}
        text = "{value}";
    }
    override var focused = false on replace {apply()};
    override var action = function () {apply()}
}

It's used the same way that a normal TextBox,
but has also a value attribute which stores the entered integer.
When the control looses the focus, it validates the value and reverts it (if isn't valid).

Answer 2

Very old thread, but this seems neater and strips out non-numeric characters if pasted.

// force the field to be numeric only
textField.textProperty().addListener(new ChangeListener<String>() {
    @Override
    public void changed(ObservableValue<? extends String> observable, String oldValue, 
        String newValue) {
        if (!newValue.matches("\\d*")) {
            textField.setText(newValue.replaceAll("[^\\d]", ""));
        }
    }
});

Answer 3

This method lets TextField to finish all processing (copy/paste/undo safe). Does not require to extend classes and allows you to decide what to do with new text after every change (to push it to logic, or turn back to previous value, or even to modify it).

  // fired by every text property change
textField.textProperty().addListener(
  (observable, oldValue, newValue) -> {
    // Your validation rules, anything you like
      // (! note 1 !) make sure that empty string (newValue.equals("")) 
      //   or initial text is always valid
      //   to prevent inifinity cycle
    // do whatever you want with newValue

    // If newValue is not valid for your rules
    ((StringProperty)observable).setValue(oldValue);
      // (! note 2 !) do not bind textProperty (textProperty().bind(someProperty))
      //   to anything in your code.  TextProperty implementation
      //   of StringProperty in TextFieldControl
      //   will throw RuntimeException in this case on setValue(string) call.
      //   Or catch and handle this exception.

    // If you want to change something in text
      // When it is valid for you with some changes that can be automated.
      // For example change it to upper case
    ((StringProperty)observable).setValue(newValue.toUpperCase());
  }
);

For your case just add this logic inside. Works perfectly.

   if (newValue.equals("")) return; 
   try {
     Integer i = Integer.valueOf(newValue);
     // do what you want with this i
   } catch (Exception e) {
     ((StringProperty)observable).setValue(oldValue);
   }

Answer 4

Here is a simple class that handles some basic validations on TextField, using TextFormatter introduced in JavaFX 8u40

EDIT:

(Code added regarding Floern's comment)

import java.text.DecimalFormatSymbols;
import java.util.regex.Pattern;

import javafx.beans.NamedArg;
import javafx.scene.control.TextFormatter;
import javafx.scene.control.TextFormatter.Change;

public class TextFieldValidator {

    private static final String CURRENCY_SYMBOL   = DecimalFormatSymbols.getInstance().getCurrencySymbol();
    private static final char   DECIMAL_SEPARATOR = DecimalFormatSymbols.getInstance().getDecimalSeparator();

    private final Pattern       INPUT_PATTERN;

    public TextFieldValidator(@NamedArg("modus") ValidationModus modus, @NamedArg("countOf") int countOf) {
        this(modus.createPattern(countOf));
    }

    public TextFieldValidator(@NamedArg("regex") String regex) {
        this(Pattern.compile(regex));
    }

    public TextFieldValidator(Pattern inputPattern) {
        INPUT_PATTERN = inputPattern;
    }

    public static TextFieldValidator maxFractionDigits(int countOf) {
        return new TextFieldValidator(maxFractionPattern(countOf));
    }

    public static TextFieldValidator maxIntegers(int countOf) {
        return new TextFieldValidator(maxIntegerPattern(countOf));
    }

    public static TextFieldValidator integersOnly() {
        return new TextFieldValidator(integersOnlyPattern());
    }

    public TextFormatter<Object> getFormatter() {
        return new TextFormatter<>(this::validateChange);
    }

    private Change validateChange(Change c) {
        if (validate(c.getControlNewText())) {
            return c;
        }
        return null;
    }

    public boolean validate(String input) {
        return INPUT_PATTERN.matcher(input).matches();
    }

    private static Pattern maxFractionPattern(int countOf) {
        return Pattern.compile("\\d*(\\" + DECIMAL_SEPARATOR + "\\d{0," + countOf + "})?");
    }

    private static Pattern maxCurrencyFractionPattern(int countOf) {
        return Pattern.compile("^\\" + CURRENCY_SYMBOL + "?\\s?\\d*(\\" + DECIMAL_SEPARATOR + "\\d{0," + countOf + "})?\\s?\\" +
                CURRENCY_SYMBOL + "?");
    }

    private static Pattern maxIntegerPattern(int countOf) {
        return Pattern.compile("\\d{0," + countOf + "}");
    }

    private static Pattern integersOnlyPattern() {
        return Pattern.compile("\\d*");
    }

    public enum ValidationModus {

        MAX_CURRENCY_FRACTION_DIGITS {
            @Override
            public Pattern createPattern(int countOf) {
                return maxCurrencyFractionPattern(countOf);
            }
        },

        MAX_FRACTION_DIGITS {
            @Override
            public Pattern createPattern(int countOf) {
                return maxFractionPattern(countOf);
            }
        },
        MAX_INTEGERS {
            @Override
            public Pattern createPattern(int countOf) {
                return maxIntegerPattern(countOf);
            }
        },

        INTEGERS_ONLY {
            @Override
            public Pattern createPattern(int countOf) {
                return integersOnlyPattern();
            }
        };

        public abstract Pattern createPattern(int countOf);
    }

}

You can use it like this:

textField.setTextFormatter(new TextFieldValidator(ValidationModus.INTEGERS_ONLY).getFormatter());

or you can instantiate it in a fxml file, and apply it to a customTextField with the according properties.

app.fxml:

<fx:define>
    <TextFieldValidator fx:id="validator" modus="INTEGERS_ONLY"/>
</fx:define>

CustomTextField.class:

public class CustomTextField {

private TextField textField;

public CustomTextField(@NamedArg("validator") TextFieldValidator validator) {
        this();
        textField.setTextFormatter(validator.getFormatter());
    }
}

Code on github

Answer 5

Try this simple code it will do the job.

DecimalFormat format = new DecimalFormat( "#.0" );
TextField field = new TextField();
field.setTextFormatter( new TextFormatter<>(c ->
{
    if ( c.getControlNewText().isEmpty() )
    {
        return c;
    }

    ParsePosition parsePosition = new ParsePosition( 0 );
    Object object = format.parse( c.getControlNewText(), parsePosition );

    if ( object == null || parsePosition.getIndex() <          c.getControlNewText().length() )
    {
        return null;
    }
    else
    {
        return c;
    }
}));

Answer 6

If you want to apply the same listener to more than one TextField here is the simplest solution:

TextField txtMinPrice, txtMaxPrice = new TextField();

ChangeListener<String> forceNumberListener = (observable, oldValue, newValue) -> {
    if (!newValue.matches("\\d*"))
      ((StringProperty) observable).set(oldValue);
};

txtMinPrice.textProperty().addListener(forceNumberListener);
txtMaxPrice.textProperty().addListener(forceNumberListener);