Update TreeView on custom TreeItem property change

I have extended TreeCell and TreeItem class. MyTreeItem contains a custom property which I use inside MyTreeCell to render graphics/font etc. The problem is when I set MyTreeCell.customProperty I'm not sure how to make the TreeView/Cell redraw.

For example:

public class MyTreeItem extends TreeItem {
    Object customProperty

    public void setCustomProperty(Object customProperty) {
        this.customProperty = customProperty

        // how to fire a change event on the TreeView?
    }
}

Any comments on the solution or (lack of) design approach appreciated.

There are at least two approaches (not including the hack of nulling the value, as suggested in the comments)

One is to manually fire a TreeModificationEvent when setting the custom property, that is in your setCustomProperty:

public class MyTreeItem extends TreeItem {
    Object customProperty

    public void setCustomProperty(Object customProperty) {
        this.customProperty = customProperty
        TreeModificationEvent<T> ev = new TreeModificationEvent<>(valueChangedEvent(), this);
        Event.fireEvent(this, ev);
    }
}

Another is to make the custom property a "real" property and let interested parties (f.i. your custom TreeCell) listen to changes of that property. For an example of how to implement (and re-wire) the listener have a look at how DefaultTreeCell handles the graphicProperty of a TreeItem.

Which to choose depends on your context: the first makes sure that all listeners to TreeModificationEvents are notified, the second allows to implement a general TreeCell taking a property (factory) of the treeItem to visualize.