Re: Problem with JavaFX ChangeListener?

Knute Johnson <>
Thu, 11 Dec 2014 18:31:21 -0800
On 12/11/2014 18:24, Arne Vajh??j wrote:

On 12/11/2014 6:08 PM, Knute Johnson wrote:

The other question I have is why does the ObservableValue require a cast
to StringProperty in both of the working examples and why do I declare
it as <? extends String>?
         class LengthListener<String> implements ChangeListener<String> {
             private final int length;

             public LengthListener(int length) {
                 this.length = length;

             @Override public void changed(
              ObservableValue<? extends String> observable,
              String oldValue,String newValue) {
                 if (newValue.length() > length)
         textField.textProperty().addListener(new LengthListener(4));

Formal type of observable:

interface javafx.beans.value.ObservableValue

Actual ype of observable:

class javafx.scene.control.TextInputControl$TextProperty
**** class
******** interface javafx.beans.value.ObservableValue

The cast is necessary!


OK, I see now. Thanks for that too Arne.


Knute Johnson

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