Recently I have developed a few components that derived the base class of UIComponent instead of Container. In most cases, things went hunky dory. However, I start to realize that some components fail miserably. For example, if my component uses ButtonBar (such as ToggleButtonBar), any interaction with the ButtonBar inside that component would throw a Type #1003 error. Upon close inspection, it has to do with a null focusManager property assignment to ButtonBar.