Swing Hacks

Create a Collections-Aware JComboBox #20

Chapter 2, Lists and Combos

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95

HACK

Using toString( ) on the strings will be the same as the default renderer,

simply drawing Proton, Neutron, and Electron in the list (see Figure 2-12).

The resulting change would look like Figure 2-13.

Using reflection for cell renderers is a very powerful concept because you

can reuse potentially complicated code with very little additional effort.

Using it to display strings is just a trivial example. Imagine you had a bunch

of objects representing entries from an RSS feed. Instead of creating a cus-

tom renderer or wrapping the entries in objects with a custom

toString( )

method, you could use the GenericListCellRenderer with getTitle( ) to

automatically call the

getTitle( ) method on the entry objects—no new

subclasses or extra code. Just a single string and the renderer takes care of

the rest. That is the power of reflection.

H A C K

#20

Create a Collections-Aware JComboBox Hack #20

You’ve moved on from Vector; your combo boxes should, too.

JComboBox is one of Swing’s oldest components. Unfortunately, it accepts

arrays of objects and

Vectors only. Now that Collections objects like List

have been part of the JDK for years, it would be nice to use them directly in

a combo box without shuffling objects in and out of arrays. Fortunately, the

JComboBox uses an MVC (Model-View-Controller) architecture, so you can

solve this problem ...