Restricting a TextField input to hexadecimal values in Java FX

Question

How can I restrict the input from the user to only hexadecimal values? With decimal notation the range is from 0 to 16383, but I would like to let the user type an hexadecimal n

Answer 1

best way to do it is with regular expressions:

yourTextField.textProperty().addListener(new ChangeListener<String>() {
        @Override
        public void changed(ObservableValue<? extends String> observable, String oldValue,
                            String newValue) {
            if (!newValue.matches("^[0-9A-F]+$")) {
                yourTextField.setText(newValue.replaceAll("[^\\d]", ""));
            }
        }
    });

Is this what your are looking for?

Answer 2

Use a TextFormatter with UnaryOperator and StringConverter<Integer> as shown below:

UnaryOperator<TextFormatter.Change> filter = change -> change.getControlNewText().matches("[0-3]?\\p{XDigit}{0,3}") ? change : null;

StringConverter<Integer> converter = new StringConverter<Integer>() {

    @Override
    public String toString(Integer object) {
        return object == null ? "" : Integer.toHexString(object);
    }

    @Override
    public Integer fromString(String string) {
        return string == null || string.isEmpty() ? null : Integer.parseInt(string, 16);
    }

};

TextFormatter<Integer> formatter = new TextFormatter<>(converter, null, filter);
textField.setTextFormatter(formatter);

The converted value is available via TextFormatter.value property. It only gets updated on pressing enter or the TextField loosing focus.

Answer 3

An idea may be to parse it into integer format first. You can use:

int value = Integer.decode("your hex value here");

if the string is not a proper value, it will throw a number format exception, however the decode function will also work for any valid integer (so something base 10 will work as well in this case).

An alternative you could try is:

int value = Integer.parseInt("hex value",16)

However for this method you will need to get rid of the "0x" header from your String

Since you are performing a check, surround it with a try catch block and whatever is caught would be an improperly formatted hex.

Furthermore if you need to check whether the value is between 0 to 16383, just use the value returned by the methods above.