Java Reference
In-Depth Information
Figure 14-18. EntryLayout in action
Table 14-2. LayoutManager methods
Method name
Description
Like
getPreferredSize()
for a component: the “best” size for the container
preferredLayoutSize(Container )
Same, but for the minimum workable size
minimumLayoutSize( Container )
Perform the layout calculations, and resize and reposition all the compon-
ents at the current size of the container
layoutContainer(Container)
Associate a constraint with a given component (you normally store these
mappings in a
java.util.Map
)
addLayoutComponent(String, Com-
ponent)
removeLayoutComponent(Component)
Remove a component from the
HashMap
If you don't need
Constraint
objects (such as
BorderLayout.NORTH
or a
GridBagCon-
straint
object), you can ignore the last two methods. Well, you can't ignore them com-
pletely. Because this is an interface, you must implement them. But they can be as simple as
{}
(i.e., a null-bodied method).
That leaves only three serious methods. The first,
preferredLayoutSize()
, normally loops
through all the components—either in the
HashMap
if using constraints, or in an array re-
turned by the container's
getComponents()
method—asking each for its preferred size and
adding them up, while partly doing the layout calculations. And
minimumLayoutSize()
is
the same for the smallest possible layout that will work. It may be possible for these methods
to delegate either to a common submethod or to invoke
layoutContainer()
, depending on
how the given layout policy works.
