NU-CCS-99-04.ps [ Readme | Copyright | Tutorial | Download | Feedback ]

Visuality, Symbolism of Components, and Visibility

A component can be visual or non-visual, may or may not be associated with an icon, and at times may be visible or invisible.

Visuality

A Java bean may be visual or non-visual. Visual beans are the most common kind. This is a natural consequence of the example set by Sun: the first beans were all GUI components, namely AWT components. JavaSoft even initially defined JavaBeans components to be ``reusable software components that can be manipulated visually in a builder tool" [8]. However, beans may also be non-visual. Non-visual beans are useful for their functionality despite not having a visual appearance. For example, an adapter between two components is very useful but need not be displayed visually in the final application.

Symbolism

A Java bean can come with or without an icon. Some beans are associated with a symbolic image, an icon, others are assigned one by the system, e.g., a label. The icon is specified by the user in the BeanInfo adjunct-class and displayed in the ToolBox window when you load a jar. The icon is also used to visually display non-visual beans at assembly time.

Visibility

A Java bean can be visible or invisible. Visibility is different than visuality . Visibility is the degree of being visible. It is possible to see visible beans. Invisible beans are hidden from the eye. Visuality, on the other hand, is the ability of being visual. A visual bean is associated with a java.awt.Component object, which is displayed (at design time), regardless of whether or not it is associated with an icon. A non-visual bean is represented visually (at assembly time) by its icon, and if it does not have one, by a system generated label. But even visual beans can be at times invisible, e.g., by invoking setVisible(false) (at either design or runtime).

NU-CCS-99-04.ps [ Readme | Copyright | Tutorial | Download | Feedback ]