JavaFX 2.2 TextField maxlength

Question

I am working on a JavaFX 2.2 project and I have a problem using the TextField control. I want to limit the number of characters that a user will be able to enter into each TextField. However I can't find a property or something like maxlength. The same problem existed in Swing and was solved this way. How to solve it for JavaFX 2.2?

Answer 1

This is a better way to do the job on a generic text field:

public static void addTextLimiter(final TextField tf, final int maxLength) {
    tf.textProperty().addListener(new ChangeListener<String>() {
        @Override
        public void changed(final ObservableValue<? extends String> ov, final String oldValue, final String newValue) {
            if (tf.getText().length() > maxLength) {
                String s = tf.getText().substring(0, maxLength);
                tf.setText(s);
            }
        }
    });
}

Works perfectly, except for that Undo bug.

Answer 2

With java8u40 we got a new class TextFormatter: one of its main responsibilities is to provide a hook into any change of text input before it gets comitted to the content. In that hook we can accept/reject or even change the proposed change.

The requirement solved in the OP's self-answer is

• the rule: restrict the length of text to shorter than n chars
• the modification: if the rule is violated, keep the last n chars as the input text and remove the excess chars at its start

Using a TextFormatter, this could be implemented like:

// here we adjust the new text 
TextField adjust = new TextField("scrolling: " + len);
UnaryOperator<Change> modifyChange = c -> {
    if (c.isContentChange()) {
        int newLength = c.getControlNewText().length();
        if (newLength > len) {
            // replace the input text with the last len chars
            String tail = c.getControlNewText().substring(newLength - len, newLength);
            c.setText(tail);
            // replace the range to complete text
            // valid coordinates for range is in terms of old text
            int oldLength = c.getControlText().length();
            c.setRange(0, oldLength);
        }
    }
    return c;
};
adjust.setTextFormatter(new TextFormatter(modifyChange));

Asides:

• modifying a property while listening to its change might lead to unexpected side-effects
• all suggested solutions on the key-level events are broken (they can't handle paste/programatic changes

Answer 3

You can do something similar to approach described here: http://fxexperience.com/2012/02/restricting-input-on-a-textfield/

class LimitedTextField extends TextField {

    private final int limit;

    public LimitedTextField(int limit) {
        this.limit = limit;
    }

    @Override
    public void replaceText(int start, int end, String text) {
        super.replaceText(start, end, text);
        verify();
    }

    @Override
    public void replaceSelection(String text) {
        super.replaceSelection(text);
        verify();
    }

    private void verify() {
        if (getText().length() > limit) {
            setText(getText().substring(0, limit));
        }

    }
};

Answer 4

The full code i used to solve my problem is the code below. I extend the TextField class like Sergey Grinev done and i added an empty constructor. To set the maxlength i added a setter method. I first check and then replace the text in the TextField because i want to disable inserting more than maxlength characters, otherwise the maxlength + 1 character will be inserted at the end of the TextField and the first charcter of the TextField will be deleted.

package fx.mycontrols;

public class TextFieldLimited extends TextField {  
    private int maxlength;
    public TextFieldLimited() {
        this.maxlength = 10;
    }
    public void setMaxlength(int maxlength) {
        this.maxlength = maxlength;
    }
    @Override
    public void replaceText(int start, int end, String text) {
        // Delete or backspace user input.
        if (text.equals("")) {
            super.replaceText(start, end, text);
        } else if (getText().length() < maxlength) {
            super.replaceText(start, end, text);
        }
    }

    @Override
    public void replaceSelection(String text) {
        // Delete or backspace user input.
        if (text.equals("")) {
            super.replaceSelection(text);
        } else if (getText().length() < maxlength) {
            // Add characters, but don't exceed maxlength.
            if (text.length() > maxlength - getText().length()) {
                text = text.substring(0, maxlength- getText().length());
            }
            super.replaceSelection(text);
        }
    }
}

Inside the fxml file i added the import (of the package that the TextFieldLimited class is existing) on the top of the file and replace the TextField tag with the custom TextFieldLimited.

<?import fx.mycontrols.*?>
.  
.  
. 
<TextFieldLimited fx:id="usernameTxtField" promptText="username" />

Inside the controller class,

on the top (property declaration),
@FXML
private TextFieldLimited usernameTxtField;

inside the initialize method,
usernameTxtField.setLimit(40);

That's all.