How to use JavaFX TextField maxlength

Question

How to use this code in my main class of JavaFX so that I can set maxlength of characters in JavaFX 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));
        }

    }
};

My JavaFX main class is given below:

public class TextFiled extends Application {
    @Override
    public void start(Stage primaryStage) {
        final TextField t_fname = new TextField();
        
        StackPane root = new StackPane();
        root.getChildren().add(t_fname);
        
        Scene scene = new Scene(root, 300, 250);
        
        primaryStage.setTitle("Hello World!");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}

score 9 · Answer 1 · edited May 23 '17 at 12:30

While the OP's technical problem is correctly answered (though not accepted), the solution to the base issue - how to restrict/validate input in a TextField which is answered in the other posts - has changed over time.

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. To fulfill the requirement of limiting the input to a certain length (and - just for fun - show a context menu with an error message) we would

implement a UnaryOperator that analyses all changes
reject those which would result into a longer text (and show the message)
accept all other changes
instantiate a TextFormatter with the operator
configure the TextField with the TextFormatter

A code snippet:

int len = 20;
TextField field = new TextField("max chars: " + len );
// here we reject any change which exceeds the length 
UnaryOperator<Change> rejectChange = c -> {
    // check if the change might effect the validating predicate
    if (c.isContentChange()) {
        // check if change is valid
        if (c.getControlNewText().length() > len) {
            // invalid change
            // sugar: show a context menu with error message
            final ContextMenu menu = new ContextMenu();
            menu.getItems().add(new MenuItem("This field takes\n"+len+" characters only."));
            menu.show(c.getControl(), Side.BOTTOM, 0, 0);
            // return null to reject the change
            return null;
        }
    }
    // valid change: accept the change by returning it
    return c;
};
field.setTextFormatter(new TextFormatter(rejectChange));

Aside:

Modifying the state of a sender while it is notifying its listeners about a change of that state is generally a bad idea and might easily lead to unexpected and hard-to-track side-effects (I suspect - though don't know - that the undo bug mentioned in other answers is such a side-effect)

score 8 · Accepted Answer · edited May 23 '17 at 12:01

8

This is my solution:

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);
            }
        }
    });
}

See JavaFX 2.2 TextField maxlength and Prefer composition over inheritance?

edited May 23 '17 at 12:01

Community

1
1

answered Mar 04 '14 at 15:36

ceklock

6,143
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beware: modifying the state of the sender during notification generally is a bad idea - you might get hard-to-track side-effects – kleopatra Oct 19 '15 at 15:15

score 6 · Answer 3 · edited Jul 23 '13 at 20:34

6

You should use your LimitedTextField instead of TextField.

Replace this line:

final TextField t_fname = new TextField();

with this one:

final LimitedTextField t_fname = new LimitedTextField(maxLength);

edited Jul 23 '13 at 20:34

GraphicsMuncher

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answered May 14 '13 at 09:00

Julien Bodin

783
3
19

score 0 · Answer 4 · 2019-08-18T03:07:45.533

This is very similar to LimitedTextField, but I feel it is more neat, because the verification is done before the textinput (and not afterwards). Also with the beep and hint the user gets some feedback, that the input was limited on purpose. The hint closes when the field looses focus.

import java.awt.Toolkit;
import javafx.scene.control.TextField;

public class DataTextField extends TextField
{
int length;
int compare;

public DataTextField(int length)
{
    super();
    this.length = length;
}

public void replaceText(int start, int end, String text)
{
    compare = getText().length() - (end - start) + text.length();
    if( compare <= length || start != end)
    {
        super.replaceText( start, end, text );
    }
    else
    {
        Toolkit.getDefaultToolkit().beep();
        show();
    }
}

public void replaceSelection(String text)
{
    compare = getText().length() + text.length();
    if( compare <= length )
    {
        super.replaceSelection( text );
    }
    else
    {
        Toolkit.getDefaultToolkit().beep();
        show();
    }
}
private void show()
{
    final ContextMenu menu = new ContextMenu();
    menu.getItems().add(new MenuItem("This field takes\n"+length+" characters only."));
    menu.show(this, Side.BOTTOM, 0, 0);
}
}

good for earlier versions! Since 8u40 we have got a new kid on the block - TextFormatter. — kleopatra, Oct 19 '15 at 15:18

score 0 · Answer 5 · answered Oct 31 '17 at 12:20

My solution to limit a TextField with a max length of characters:

        final int maxLength = 20;

        textField.setOnKeyTyped(t -> {

            if (textField.getText().length() > maxLength) {
                int pos = textField.getCaretPosition();
                textField.setText(textField.getText(0, maxLength));
                textField.positionCaret(pos); //To reposition caret since setText sets it at the beginning by default
            }

        });

How to use JavaFX TextField maxlength

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