Painting and Repainting
Our last topic in this chapter
deals with repainting in Swing. Repainting is a somewhat arcane topic
that most people don’t really feel the need to talk about. This
section is orchestrated to give you a better feel for how painting
and repainting via the repaint manager and
JComponent works. You typically do not need to get
involved with the
RepaintManager class, and only
the extremely brave will override it. However, there are some
instances where a firm understanding of the repaint manager can avoid
Recall that Swing uses lightweight components, which are drawn inside
heavyweight top-level containers. Hence, the operating system will
not deal with the repainting of those components. To continue the
analogy first presented in the lightweight and heavyweight discussion
earlier, Swing is responsible for painting and repainting everything
inside of its own easels. Consequently, Swing delegates this duty to
RepaintManager class to organize and schedule
repainting when told to do so.
The RepaintManager Class
class is responsible for painting and
repainting parts of components that have become
dirty, or regions that need to be repainted.
Note that the “dirty region” does not necessarily include
the entire region of the component, but often only a portion of it.
RepaintManager is also charged with the second responsibility of revalidating components that have been marked invalid. Both responsibilities ultimately ...