Limiting character count of JavaFX TextField causes IndexOutOfBounds on Undo

Question

I have the requirement to limit the number of characters a user can input into a TextField JavaFX control. I have extended TextField like so

public class LengthLimitedTextField extends TextField {
    /**
     * @param maxCharacters The max allowed characters that can be entered into this {@link TextField}.
     */
    public LengthLimitedTextField(final int maxCharacters) {
        final TextField thisField = this;
        this.textProperty().addListener(new ChangeListener<String>() {
            @Override
            public void changed(ObservableValue<? extends String> observable,
                                String oldValue, String newValue) {
                // Force correct length by deleting the last entered character if text is longer than maxCharacters
                if (newValue.length() > maxCharacters) {
                    thisField.deleteNextChar();
                }
            }
        });
    }
}

This does work as intended. However, lets say that for a particular LengthLimitedTextField the maxCharacters is set to 3. If the user enters 4 or more characters, and attempts to Undo (either via CTRL+Z or mouse context menu), I receive the following Exception and the text is left unchanged.

java.lang.IndexOutOfBoundsException
    at javafx.scene.control.TextInputControl.replaceText(TextInputControl.java:368)
    at com.sun.javafx.scene.control.skin.TextFieldSkin.replaceText(TextFieldSkin.java:572)
    at com.sun.javafx.scene.control.behavior.TextFieldBehavior.replaceText(TextFieldBehavior.java:159)
    at com.sun.javafx.scene.control.behavior.TextInputControlBehavior$UndoManager.undo(TextInputControlBehavior.java:442)
    at com.sun.javafx.scene.control.behavior.TextInputControlBehavior.callAction(TextInputControlBehavior.java:137)
    at com.sun.javafx.scene.control.skin.TextInputControlSkin$ContextMenuItem$1.handle(TextInputControlSkin.java:595)
    at com.sun.javafx.scene.control.skin.TextInputControlSkin$ContextMenuItem$1.handle(TextInputControlSkin.java:593)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:69)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:28)
    at javafx.event.Event.fireEvent(Event.java:171)
    at javafx.scene.control.MenuItem.fire(MenuItem.java:456)
    at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.doSelect(ContextMenuContent.java:1197)
    at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer$6.handle(ContextMenuContent.java:1148)
    at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer$6.handle(ContextMenuContent.java:1146)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:69)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:33)
    at javafx.event.Event.fireEvent(Event.java:171)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3328)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3168)
    at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3123)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1563)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2265)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:250)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:173)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:292)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:528)
    at com.sun.glass.ui.View.notifyMouse(View.java:922)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:29)
    at com.sun.glass.ui.win.WinApplication$3$1.run(WinApplication.java:73)
    at java.lang.Thread.run(Thread.java:724)

I'm not sure how I can resolve this. A possible (but not ideal) solution was to disable Undo/Redo completely, but that doesn't appear possible without completely override the context menu (which according to this SO answer, isn't easy) and the default keyboard shortcuts.

So ultimately, my question is twofold:

Is there possibly another way I can limit the number of characters of a TextField without throwing an exception on Undo? Or is there a clean way to completely disable Undo in the application?

Edit: I did some more research and according to https://javafx-jira.kenai.com/browse/RT-30881 this appears to be a bug. See this comment. So perhaps this isn't possible to achieve then? I'm going to leave the question open in hopes someone does have a possible workaround.

Answer 1

Here how I would do it: I would use a normal textfield, and would add an event filter.

The set up:

TextField tx = new TextField();
        tx.addEventFilter(KeyEvent.KEY_TYPED, maxLength(3));

The event handler:

public EventHandler<KeyEvent> maxLength(final Integer i) {
        return new EventHandler<KeyEvent>() {

            @Override
            public void handle(KeyEvent arg0) {

                TextField tx = (TextField) arg0.getSource();
                if (tx.getText().length() >= i) {
                    arg0.consume();
                }

            }

        };

    }

Answer 2

Here is another solution using Lambda Expressions on JavaFX 8

textField.textProperty().addListener(
        (observable,oldValue,newValue)-> {
            if(newValue.length() > 5) cp.setText(oldValue);
        }
);

If textField length is more than 5 it doesn't insert more text.

Answer 3

adding a little spices to Magcus code

@FXML
private TextField txt_Numeric;
@FXML
private TextField txt_Letters;

@Override
public void initialize(URL url, ResourceBundle rb) {
    /* add Event Filter to your TextFields **************************************************/
    txt_Numeric.addEventFilter(KeyEvent.KEY_TYPED , numeric_Validation(10));
    txt_Letters.addEventFilter(KeyEvent.KEY_TYPED , letter_Validation(10));
}

/* Numeric Validation Limit the  characters to maxLengh AND to ONLY DigitS *************************************/
public EventHandler<KeyEvent> numeric_Validation(final Integer max_Lengh) {
    return new EventHandler<KeyEvent>() {
        @Override
        public void handle(KeyEvent e) {
            TextField txt_TextField = (TextField) e.getSource();                
            if (txt_TextField.getText().length() >= max_Lengh) {                    
                e.consume();
            }
            if(e.getCharacter().matches("[0-9.]")){ 
                if(txt_TextField.getText().contains(".") && e.getCharacter().matches("[.]")){
                    e.consume();
                }else if(txt_TextField.getText().length() == 0 && e.getCharacter().matches("[.]")){
                    e.consume(); 
                }
            }else{
                e.consume();
            }
        }
    };
}    
/*****************************************************************************************/

 /* Letters Validation Limit the  characters to maxLengh AND to ONLY Letters *************************************/
public EventHandler<KeyEvent> letter_Validation(final Integer max_Lengh) {
    return new EventHandler<KeyEvent>() {
        @Override
        public void handle(KeyEvent e) {
            TextField txt_TextField = (TextField) e.getSource();                
            if (txt_TextField.getText().length() >= max_Lengh) {                    
                e.consume();
            }
            if(e.getCharacter().matches("[A-Za-z]")){ 
            }else{
                e.consume();
            }
        }
    };
}    
/*****************************************************************************************/

best of luck. ^^

Answer 4

This method let TextField to finish all processing (copy/paste/undo safe). Do not requares to make extending class. And allow you to deside 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.

    // For example 10 characters     
  if (newValue.length() >= 10) ((StringProperty)observable).setValue(oldValue);