Manually typing in text in JavaFX Spinner is not u

问题:

It seems that the Spinner control does not update a manually typed-in value until the user explicitly presses enter. So, they could type in a value (not press enter) exit the control, and submit the form, and the value displayed in the spinner is NOT the value of the Spinner, it is the old value.

My idea was to add a listener to the lost focus event, but I can't see a way to gain access to the typed-in value?

spinner.focusedProperty().addListener((observable, oldValue, newValue) -> 
{
    //if focus lost
    if(!newValue)
    {
        //somehow get the text the user typed in?
    }
});

This is odd behavior, it seems to go against the convention of a GUI spinner control.

回答1:

Unfortunately, Spinner doesn't behave as expected: in most OS, it should commit the edited value on focus lost. Even more unfortunate, it doesn't provide any configuration option to easily make it behave as expected.

So we have to manually commit the value in a listener to the focusedProperty. On the bright side, Spinner already has code doing so - it's private, though, we have to c&p it

/**
 * c&p from Spinner
 */
private <T> void commitEditorText(Spinner<T> spinner) {
    if (!spinner.isEditable()) return;
    String text = spinner.getEditor().getText();
    SpinnerValueFactory<T> valueFactory = spinner.getValueFactory();
    if (valueFactory != null) {
        StringConverter<T> converter = valueFactory.getConverter();
        if (converter != null) {
            T value = converter.fromString(text);
            valueFactory.setValue(value);
        }
    }
}

// useage in client code
spinner.focusedProperty().addListener((s, ov, nv) -> {
    if (nv) return;
    //intuitive method on textField, has no effect, though
    //spinner.getEditor().commitValue(); 
    commitEditorText(spinner);
});

Note that there's a method

textField.commitValue()

which I would have expected to ... well ... commit the value, which has no effect. It's (final!) implemented to update the value of the textFormatter if available. Doesn't work in the Spinner, even if you use a textFormatter for validation. Might be some internal listener missing or the spinner not yet updated to the relatively new api - didn't dig, though.

---

Update

While playing around a bit more with TextFormatter I noticed that a formatter guarantees to commit on focusLost:

The value is updated when the control loses its focus or it is commited (TextField only)

Which indeed works as documented such that we could add a listener to the formatter's valueProperty to get notified whenever the value is committed:

TextField field = new TextField();
TextFormatter fieldFormatter = new TextFormatter(
      TextFormatter.IDENTITY_STRING_CONVERTER, "initial");
field.setTextFormatter(fieldFormatter);
fieldFormatter.valueProperty().addListener((s, ov, nv) -> {
    // do stuff that needs to be done on commit
} );

Triggers for a commit:

• user hits ENTER
• control looses focus
• field.setText is called programmatically (this is undocumented behaviour!)

Coming back to the spinner: we can use this commit-on-focusLost behaviour of a formatter's value to force a commit on the spinnerFactory's value. Something like

// normal setup of spinner
SpinnerValueFactory factory = new IntegerSpinnerValueFactory(0, 10000, 0);
spinner.setValueFactory(factory);
spinner.setEditable(true);
// hook in a formatter with the same properties as the factory
TextFormatter formatter = new TextFormatter(factory.getConverter(), factory.getValue());
spinner.getEditor().setTextFormatter(formatter);
// bidi-bind the values
factory.valueProperty().bindBidirectional(formatter.valueProperty());

Note that editing (either typing or programmatically replacing/appending/pasting text) does not trigger a commit - so this cannot be used if commit-on-text-change is needed.

回答2:

@kleopatra headed to a right direction, but the copy-paste solution feels awkward and the TextFormatter-based one did not work for me at all. So here's a shorter one, which forces Spinner to call it's private commitEditorText() as desired:

spinner.focusedProperty().addListener((observable, oldValue, newValue) -> {
  if (!newValue) {
    spinner.increment(0); // won't change value, but will commit editor
  }
});

回答3:

This is standard behavior for the control according to the documentation:

The editable property is used to specify whether user input is able to be typed into the Spinner editor. If editable is true, user input will be received once the user types and presses the Enter key. At this point the input is passed to the SpinnerValueFactory converter StringConverter.fromString(String) method. The returned value from this call (of type T) is then sent to the SpinnerValueFactory.setValue(Object) method. If the value is valid, it will remain as the value. If it is invalid, the value factory will need to react accordingly and back out this change.

Perhaps you could use a keyboard event to listen to and call the edit commit on the control as you go.

回答4:

Here is an improved variant of Sergio's solution.

The initialize method will attach Sergio's code to all Spinners in the controller.

public void initialize(URL location, ResourceBundle resources) {
    for (Field field : getClass().getDeclaredFields()) {
        try {
            Object obj = field.get(this);
            if (obj != null && obj instanceof Spinner)
                ((Spinner) obj).focusedProperty().addListener((observable, oldValue, newValue) -> {
                    if (!newValue) {
                        ((Spinner) obj).increment(0);
                    }
                });
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
    }
}

回答5:

Using a listener should work. You can get access to the typed in value through the spinner's editor:

spinner.getEditor().getText();

回答6:

I use an alternate approach - update it live while typing. This is my current implementation:

getEditor().textProperty().addListener { _, _, nv ->
    // let the user clear the field without complaining
    if(nv.isNotEmpty()) {
        Double newValue = getValue()
        try {
            newValue = getValueFactory().getConverter().fromString(nv)
        } catch (Exception e) { /* user typed an illegal character */ } 
        getValueFactory().setValue(newValue)
    }