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java.awt
Class Choice

java.lang.Object
  java.awt.Component
      java.awt.Choice

All Implemented Interfaces:

ImageObserver, ItemSelectable, MenuContainer, Serializable, Accessible

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.

Since:

JDK1.0

See Also:

Serialized Form

Nested Class Summary

protected class

Choice.AccessibleAWTChoice 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

BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT

Fields inherited from interface java.awt.image.ImageObserver

ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH

Constructor Summary

Choice()
Creates a new choice menu.

Method Summary

void	add(String item) Adds an item to this Choice menu.
void	addItem(String item) Obsolete as of Java 2 platform v1.1.
void	addItemListener(ItemListener l) Adds the specified item listener to receive item events from this Choice menu.
void	addNotify() Creates the Choice's peer.
int	countItems() Deprecated. As of JDK version 1.1, replaced by getItemCount().
AccessibleContext	getAccessibleContext() Gets the AccessibleContext associated with this Choice.
String	getItem(int index) Gets the string at the specified index in this Choice menu.
int	getItemCount() Returns the number of items in this Choice menu.
ItemListener[]	getItemListeners() Returns an array of all the item listeners registered on this choice.
<T extends EventListener> T[]	getListeners(Class<T> listenerType) Returns an array of all the objects currently registered as FooListeners upon this Choice.
int	getSelectedIndex() Returns the index of the currently selected item.
String	getSelectedItem() Gets a representation of the current choice as a string.
Object[]	getSelectedObjects() Returns an array (length 1) containing the currently selected item.
void	insert(String item, int index) Inserts the item into this choice at the specified position.
protected String	paramString() Returns a string representing the state of this Choice menu.
protected void	processEvent(AWTEvent e) Processes events on this choice.
protected void	processItemEvent(ItemEvent e) 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	remove(String item) Removes the first occurrence of item from the Choice menu.
void	removeAll() Removes all items from the choice menu.
void	removeItemListener(ItemListener l) 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	select(String str) 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.awt.Component

action, add, addComponentListener, addFocusListener, addHierarchyBoundsListener, addHierarchyListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addMouseWheelListener, addPropertyChangeListener, addPropertyChangeListener, applyComponentOrientation, areFocusTraversalKeysSet, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, createVolatileImage, createVolatileImage, deliverEvent, disable, disableEvents, dispatchEvent, doLayout, enable, enable, enableEvents, enableInputMethods, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, getAlignmentX, getAlignmentY, getBackground, getBaseline, getBaselineResizeBehavior, getBounds, getBounds, getColorModel, getComponentAt, getComponentAt, getComponentListeners, getComponentOrientation, getCursor, getDropTarget, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeys, getFocusTraversalKeysEnabled, getFont, getFontMetrics, getForeground, getGraphics, getGraphicsConfiguration, getHeight, getHierarchyBoundsListeners, getHierarchyListeners, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getLocale, getLocation, getLocation, getLocationOnScreen, getMaximumSize, getMinimumSize, getMouseListeners, getMouseMotionListeners, getMousePosition, getMouseWheelListeners, getName, getParent, getPeer, getPreferredSize, getPropertyChangeListeners, getPropertyChangeListeners, getSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, invalidate, isBackgroundSet, isCursorSet, isDisplayable, isDoubleBuffered, isEnabled, isFocusable, isFocusCycleRoot, isFocusOwner, isFocusTraversable, isFontSet, isForegroundSet, isLightweight, isMaximumSizeSet, isMinimumSizeSet, isOpaque, isPreferredSizeSet, isShowing, isValid, isVisible, keyDown, keyUp, layout, list, list, list, list, list, locate, location, lostFocus, minimumSize, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paint, paintAll, postEvent, preferredSize, prepareImage, prepareImage, print, printAll, processComponentEvent, processFocusEvent, processHierarchyBoundsEvent, processHierarchyEvent, processInputMethodEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, processMouseWheelEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, removeNotify, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, reshape, resize, resize, setBackground, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setEnabled, setFocusable, setFocusTraversalKeys, setFocusTraversalKeysEnabled, setFont, setForeground, setIgnoreRepaint, setLocale, setLocation, setLocation, setMaximumSize, setMinimumSize, setName, setPreferredSize, setSize, setSize, setVisible, show, show, size, toString, transferFocus, transferFocusBackward, transferFocusUpCycle, update, validate

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Choice

public Choice()
       throws HeadlessException

Creates a new choice menu. The menu initially has no items in it.

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.

Throws:

HeadlessException - if GraphicsEnvironment.isHeadless() returns true

See Also:

GraphicsEnvironment.isHeadless(), select(int), select(java.lang.String)

Method Detail

addNotify

public void addNotify()

Creates the Choice's peer. This peer allows us to change the look of the Choice without changing its functionality.

Overrides:

addNotify in class Component

See Also:

Toolkit.createChoice(java.awt.Choice), Component.getToolkit()

getItemCount

public int getItemCount()

Returns the number of items in this Choice menu.

Returns:

the number of items in this Choice menu

Since:

JDK1.1

See Also:

getItem(int)

countItems

@Deprecated
public int countItems()

Deprecated. As of JDK version 1.1, replaced by getItemCount().

getItem

public String getItem(int index)

Gets the string at the specified index in this Choice menu.

Parameters:

index - the index at which to begin

See Also:

getItemCount()

add

public void add(String item)

Adds an item to this Choice menu.

Parameters:

item - the item to be added

Throws:

NullPointerException - if the item's value is null

Since:

JDK1.1

addItem

public void addItem(String item)

Obsolete as of Java 2 platform v1.1. Please use the add method instead.

Adds an item to this Choice menu.

Parameters:

item - the item to be added

Throws:

NullPointerException - if the item's value is equal to null

insert

public void insert(String item,
                   int index)

Inserts the item into this choice at the specified position. Existing items at an index greater than or equal to 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.

Parameters:

item - the non-null item to be inserted

index - the position at which the item should be inserted

Throws:

IllegalArgumentException - if index is less than 0

remove

public void remove(String item)

Removes the first occurrence of 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).

Parameters:

item - the item to remove from this Choice menu

Throws:

IllegalArgumentException - if the item doesn't exist in the choice menu

Since:

JDK1.1

remove

public void remove(int position)

Removes an item from the choice menu at the specified position. 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).

Parameters:

position - the position of the item

Throws:

IndexOutOfBoundsException - if the specified position is out of bounds

Since:

JDK1.1

removeAll

public void removeAll()

Removes all items from the choice menu.

Since:

JDK1.1

See Also:

remove(java.lang.String)

getSelectedItem

public String getSelectedItem()

Gets a representation of the current choice as a string.

Returns:

a string representation of the currently selected item in this choice menu

See Also:

getSelectedIndex()

getSelectedObjects

public Object[] getSelectedObjects()

Returns an array (length 1) containing the currently selected item. If this choice has no items, returns null.

Specified by:

getSelectedObjects in interface ItemSelectable

See Also:

ItemSelectable

getSelectedIndex

public int getSelectedIndex()

Returns the index of the currently selected item. If nothing is selected, returns -1.

Returns:

the index of the currently selected item, or -1 if nothing is currently selected

See Also:

getSelectedItem()

select

public void select(int pos)

Sets the selected item in this 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.

Parameters:

pos - the positon of the selected item

Throws:

IllegalArgumentException - if the specified position is greater than the number of items or less than zero

See Also:

getSelectedItem(), getSelectedIndex()

select

public void select(String str)

Sets the selected item in this 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.

Parameters:

str - the specified string

See Also:

getSelectedItem(), getSelectedIndex()

addItemListener

public void addItemListener(ItemListener l)

Adds the specified item listener to receive item events from this 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.

Specified by:

addItemListener in interface ItemSelectable

Parameters:

l - the item listener

Since:

JDK1.1

See Also:

removeItemListener(java.awt.event.ItemListener), getItemListeners(), select(int), ItemEvent, ItemListener

removeItemListener

public void removeItemListener(ItemListener l)

Removes the specified item listener so that it no longer receives item events from this 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.

Specified by:

removeItemListener in interface ItemSelectable

Parameters:

l - the item listener

Since:

JDK1.1

See Also:

addItemListener(java.awt.event.ItemListener), getItemListeners(), ItemEvent, ItemListener

getItemListeners

public ItemListener[] getItemListeners()

Returns an array of all the item listeners registered on this choice.

Returns:

all of this choice's ItemListeners or an empty array if no item listeners are currently registered

Since:

1.4

See Also:

addItemListener(java.awt.event.ItemListener), removeItemListener(java.awt.event.ItemListener), ItemEvent, ItemListener

getListeners

public <T extends EventListener> T[] getListeners(Class<T> listenerType)

Returns an array of all the objects currently registered as FooListeners upon this Choice. FooListeners 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.

Overrides:

getListeners in class Component

Parameters:

listenerType - the type of listeners requested; this parameter should specify an interface that descends from java.util.EventListener

Returns:

an array of all objects registered as FooListeners on this choice, or an empty array if no such listeners have been added

Throws:

ClassCastException - if listenerType doesn't specify a class or interface that implements java.util.EventListener

Since:

1.3

See Also:

getItemListeners()

processEvent

protected void processEvent(AWTEvent e)

Processes events on this choice. If the event is an instance of 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.

Overrides:

processEvent in class Component

Parameters:

e - the event

Since:

JDK1.1

See Also:

ItemEvent, processItemEvent(java.awt.event.ItemEvent)

processItemEvent

protected void processItemEvent(ItemEvent e)

Processes item events occurring on this 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:

• An ItemListener object is registered via addItemListener.
• Item events are enabled via enableEvents.

Note that if the event parameter is null the behavior is unspecified and may result in an exception.

Parameters:

e - the item event

Since:

JDK1.1

See Also:

ItemEvent, ItemListener, addItemListener(ItemListener), Component.enableEvents(long)

paramString

protected String paramString()

Returns a string representing the state of this 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.

Overrides:

paramString in class Component

Returns:

the parameter string of this Choice menu

getAccessibleContext

public AccessibleContext getAccessibleContext()

Gets the AccessibleContext associated with this Choice. For Choice components, the AccessibleContext takes the form of an AccessibleAWTChoice. A new AccessibleAWTChoice instance is created if necessary.

Specified by:

getAccessibleContext in interface Accessible

Overrides:

getAccessibleContext in class Component

Returns:

an AccessibleAWTChoice that serves as the AccessibleContext of this Choice

Since:

1.3