Lists and Forms - Beginning J2ME: From Novice to Professional - page 84

else if (c == mIdleCommand) {
mContinuousGauge.setValue(Gauge.CONTINUOUS_IDLE);
mIncrementalGauge.setValue(Gauge.INCREMENTAL_IDLE);
}
}
}

ChoiceGroup
Another class in the Form arsenal of Item s is ChoiceGroup . ChoiceGroup offers a list of choices. It
is very similar to javax.microedition.lcdui.List , which was described at the beginning of this
chapter. This similarity is more than coincidental; ChoiceGroup and List both implement the
Choice interface, which is the wellspring of all of the instance methods in both classes.
If you read the section about List , you already know almost everything you need to know
to use ChoiceGroup because the instance methods work exactly the same way.
ChoiceGroup features the following constructors:

public ChoiceGroup(String label, int choiceType)
public ChoiceGroup(String label, int choiceType, String[] stringElements,
Image[] imageElements)

The choiceType should look familiar; it can be either EXCLUSIVE or MULTIPLE , the constants
defined in the Choice interface. In fact, ChoiceGroup 's constructors work exactly like List 's
constructors, except that IMPLICIT is not allowed. This makes sense, since a ChoiceGroup is one
item in a form, not an entire screen. There is also a POPUP type for ChoiceGroup that makes it
appear like a combo box or a drop-down menu. The ChoiceGroup appears like any other element
in the Form ; Figure 6-12 shows examples.

(a) (b) (c)

Figure 6-12. ChoiceGroup examples: (a) MULTIPLE, (b) EXCLUSIVE, and (c) POPUP