The CheckboxGroup lets multiple
checkboxes work together to provide a mutually exclusion choice (at most
one Checkbox can be selected
at a time). Because the CheckboxGroup
is neither a Component nor a
Container, you should normally
put all the Checkbox components
associated with a CheckboxGroup
in their own Panel (or other
Container). The LayoutManager
of the Panel should be GridLayout
(0, 1) if you want them in one column. Figure 9.5 shows both a good way and bad way of positioning
a set of Checkbox items in
a CheckboxGroup. The image
on the left is preferred because the user can sense that the items are
grouped; the image on the right suggests three levels of different checkboxes
and can therefore surprise the user when checkboxes are deselected.
Constructors
- public CheckboxGroup ()
-
This constructor creates an instance of CheckboxGroup.
Miscellaneous methods
- public int getSelectedCheckbox ()
public Checkbox getCurrent ()
-
The getSelectedCheckbox() method
returns the Checkbox within
the CheckboxGroup whose value
is true. If no item is selected,
null is returned.
getCurrent() is the Java 1.0
name for this method.
- public synchronized void setSelectedCheckbox (Checkbox checkbox)
public synchronized void setCurrent (Checkbox checkbox)
-
The setSelectedCheckbox() method
makes checkbox the currently
selected Checkbox within the
CheckboxGroup. If checkboxis null,
the method deselects all the items in the CheckboxGroup.
If checkbox is not within the
CheckboxGroup, nothing happens.
setCurrent() is the Java 1.0
name for this method.
- public String toString ()
-
The toString() method of CheckboxGroup
creates a String representation
of the current choice (as returned by getSelectedCheckbox()).
Using the "straightforward" layout in Figure 9.5 as an example,
the results would be:
java.awt.CheckboxGroup[current=java.awt.Checkbox[0,31,85x21,
label=Helvetica,state=true]]
If there is no currently selected item, the results within the square brackets
would be current=null.
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