Even in this time of total NSA surveillance it is still a good idea to implement your JavaFX controls with observability in mind. This is easy to achieve in JavaFX especially compared to Swing.
The Old Days
Coming from Swing I was used to spending a lot of energy and time on making custom controls observable. It usually required adding methods to add and remove listeners of a certain type. This listener type was a new interface, the single method of that interface accepted a new event object. To send this event object the control had to “fire” it inside my custom control, so I ended up writing fireXYZ() methods. A lot of work only to let somebody know that some aspect of the control’s state has changed.
The New Age
In JavaFX observability can be achieved much more easily by using properties and observable collections. In the FlexGanttFX framework almost every attribute of its controls are properties and all collections are created via the FXCollections class, which returns observable collections. This makes a lot of sense because the total of the attributes of each control defines its state and this state needs to be observable so that other parts of the application (especially other controls) can react to state changes.
The downside of using properties is that you end up writing a lot of boilerplate code but still much less than in Swing. In the case of a boolean property it will look like this: