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public class Choice extends Component implements ItemSelectable, Accessible
The Choice
class presents a pop-up menu of choices.
The current choice is displayed as the title of the menu.
The following code example produces a pop-up menu:
Choice ColorChooser = new Choice(); ColorChooser.add("Green"); ColorChooser.add("Red"); ColorChooser.add("Blue");
After this choice menu has been added to a panel, it appears as follows in its normal state:
In the picture, "Green"
is the current choice.
Pushing the mouse button down on the object causes a menu to
appear with the current choice highlighted.
Some native platforms do not support arbitrary resizing of
Choice
components and the behavior of
setSize()/getSize()
is bound by
such limitations.
Native GUI Choice
components' size are often bound by such
attributes as font size and length of items contained within
the Choice
.
Nested Class Summary | |
---|---|
protected class |
This class implements accessibility support for the Choice class. |
Nested classes/interfaces inherited from class java.awt.Component |
---|
Component.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy |
Field Summary |
---|
Fields inherited from class java.awt.Component |
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BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT |
Constructor Summary | |
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Choice() Creates a new choice menu. |
Method Summary | |
---|---|
void |
Adds an item to this Choice menu.
|
void |
Obsolete as of Java 2 platform v1.1. |
void |
Adds the specified item listener to receive item events from this Choice menu.
|
void |
Creates the Choice 's peer.
|
int |
|
AccessibleContext |
Gets the AccessibleContext associated with this
Choice .
|
String |
getItem(int index) Gets the string at the specified index in this Choice menu.
|
int |
Returns the number of items in this Choice menu.
|
ItemListener[] |
Returns an array of all the item listeners registered on this choice. |
EventListener[] |
getListeners(Class listenerType) Returns an array of all the objects currently registered as FooListener s
upon this Choice .
|
int |
Returns the index of the currently selected item. |
String |
Gets a representation of the current choice as a string. |
Object[] |
Returns an array (length 1) containing the currently selected item. |
void |
Inserts the item into this choice at the specified position. |
protected String |
Returns a string representing the state of this Choice
menu.
|
protected void |
Processes events on this choice. |
protected void |
Processes item events occurring on this Choice
menu by dispatching them to any registered
ItemListener objects.
|
void |
remove(int position) Removes an item from the choice menu at the specified position. |
void |
Removes the first occurrence of item
from the Choice menu.
|
void |
Removes all items from the choice menu. |
void |
Removes the specified item listener so that it no longer receives item events from this Choice menu.
|
void |
select(int pos) Sets the selected item in this Choice menu to be the
item at the specified position.
|
void |
Sets the selected item in this Choice menu
to be the item whose name is equal to the specified string.
|
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public Choice() throws HeadlessException
By default, the first item added to the choice menu becomes the
selected item, until a different selection is made by the user
by calling one of the select
methods.
HeadlessException
- if GraphicsEnvironment.isHeadless()
returns trueMethod Detail |
---|
public void add(String item)
Choice
menu.
item
- the item to be addedpublic void addItem(String item)
add
method instead.
Adds an item to this Choice
menu.
item
- the item to be addedpublic synchronized void addItemListener(ItemListener l)
Choice
menu. Item events are sent in response
to user input, but not in response to calls to select
.
If l is null
, no exception is thrown and no action
is performed.
Refer to AWT Threading Issues for details on AWT's threading model.
l
- the item listenerpublic void addNotify()
Choice
's peer. This peer allows us
to change the look
of the Choice
without changing its functionality.
addNotify
in class Component
public int countItems()
public AccessibleContext getAccessibleContext()
AccessibleContext
associated with this
Choice
. For Choice
components,
the AccessibleContext
takes the form of an
AccessibleAWTChoice
. A new AccessibleAWTChoice
instance is created if necessary.
getAccessibleContext
in class Component
AccessibleAWTChoice
that serves as the
AccessibleContext
of this Choice
public String getItem(int index)
Choice
menu.
index
- the index at which to beginpublic int getItemCount()
Choice
menu.
Choice
menupublic synchronized ItemListener[] getItemListeners()
ItemListener
s
or an empty array if no item
listeners are currently registeredpublic EventListener[] getListeners(Class listenerType)
FooListener
s
upon this Choice
.
FooListener
s are registered using the
addFooListener
method.
You can specify the listenerType
argument
with a class literal, such as
FooListener.class
.
For example, you can query a
Choice
c
for its item listeners with the following code:
ItemListener[] ils = (ItemListener[])(c.getListeners(ItemListener.class));If no such listeners exist, this method returns an empty array.
getListeners
in class Component
listenerType
- the type of listeners requested; this parameter
should specify an interface that descends from
java.util.EventListener
FooListener
s on this choice,
or an empty array if no such
listeners have been addedpublic int getSelectedIndex()
public synchronized String getSelectedItem()
public synchronized Object[] getSelectedObjects()
null
.
public void insert(String item, int index)
index
are shifted up by one to accommodate
the new item. If index
is greater than or
equal to the number of items in this choice,
item
is added to the end of this choice.
If the item is the first one being added to the choice, then the item becomes selected. Otherwise, if the selected item was one of the items shifted, the first item in the choice becomes the selected item. If the selected item was no among those shifted, it remains the selected item.
item
- the non-null
item to be insertedindex
- the position at which the item should be insertedprotected String paramString()
Choice
menu. This method is intended to be used only for debugging purposes,
and the content and format of the returned string may vary between
implementations. The returned string may be empty but may not be
null
.
paramString
in class Component
Choice
menuprotected void processEvent(AWTEvent e)
ItemEvent
, it invokes the
processItemEvent
method. Otherwise, it calls its
superclass's processEvent
method.
Note that if the event parameter is null
the behavior is unspecified and may result in an
exception.
processEvent
in class Component
e
- the eventprotected void processItemEvent(ItemEvent e)
Choice
menu by dispatching them to any registered
ItemListener
objects.
This method is not called unless item events are enabled for this component. Item events are enabled when one of the following occurs:
ItemListener
object is registered
via addItemListener
.
enableEvents
.
Note that if the event parameter is null
the behavior is unspecified and may result in an
exception.
e
- the item eventpublic void remove(int position)
position
- the position of the itempublic void remove(String item)
item
from the Choice
menu. If the item
being removed is the currently selected item,
then the first item in the choice becomes the
selected item. Otherwise, the currently selected
item remains selected (and the selected index is
updated accordingly).
item
- the item to remove from this Choice
menupublic void removeAll()
public synchronized void removeItemListener(ItemListener l)
Choice
menu.
If l is null
, no exception is thrown and no
action is performed.
Refer to AWT Threading Issues for details on AWT's threading model.
l
- the item listenerpublic synchronized void select(int pos)
Choice
menu to be the
item at the specified position.
Note that this method should be primarily used to
initially select an item in this component.
Programmatically calling this method will not trigger
an ItemEvent
. The only way to trigger an
ItemEvent
is by user interaction.
pos
- the positon of the selected itempublic synchronized void select(String str)
Choice
menu
to be the item whose name is equal to the specified string.
If more than one item matches (is equal to) the specified string,
the one with the smallest index is selected.
Note that this method should be primarily used to
initially select an item in this component.
Programmatically calling this method will not trigger
an ItemEvent
. The only way to trigger an
ItemEvent
is by user interaction.
str
- the specified string
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