JavaFX: Storing null in a SimpleIntegerProperty

问题

I have a SimpleIntegerProperty which should be able to store null. However, this is not possible, as written in the JavaDoc of IntegerProperty:

Note: setting or binding this property to a null value will set the property to "0.0". See setValue(java.lang.Number).

This also applies to other properties, such as LongProperty, FloatProperty, DoubleProperty, and BooleanProperty (but not to StringProperty, which allows null!). Why is this the case? Is there a workaround to store null in these properties?

回答1:

The IntegerProperty.setValue(java.lang.Number) method is specified in the interfaces WriteableIntegerValue and WriteableValue. The JavaDoc of WriteableIntegerValue, states:

Note: this method should accept null without throwing an exception, setting "0" instead.

If you are looking at the code of the IntegerPropertyBase class, you can also see that the value is actually stored as a primitive int (which never can be null). This is also specified in the JavaFX API of SimpleIntegerProperty:

This class provides a full implementation of a Property wrapping a int value.

Solution: You can simply circumvent that by using a SimpleObjectProperty<Integer> instead of a SimpleIntegerProperty, as a SimpleObjectProperty allows null values

来源：https://stackoverflow.com/questions/42160795/javafx-storing-null-in-a-simpleintegerproperty