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:
- 1.0
- See Also:
- Serialized Form
Nested Class Summary
Modifier and Type | Class | Description |
---|---|---|
protected class | Choice.AccessibleAWTChoice | This class implements accessibility support for the |
Nested classes/interfaces declared in class java.awt.Component
Component.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy
Field Summary
Fields declared in class java.awt.Component
accessibleContext, BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT
Fields declared in interface java.awt.image.ImageObserver
ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH
Constructor Summary
Constructor | Description |
---|---|
Choice() | Creates a new choice menu. |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
void | add(String item) | Adds an item to this |
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 |
void | addNotify() | Creates the |
int | countItems() | Deprecated. As of JDK version 1.1, replaced by getItemCount() . |
AccessibleContext | getAccessibleContext() | Gets the |
String | getItem(int index) | Gets the string at the specified index in this |
int | getItemCount() | Returns the number of items in this |
ItemListener[] | getItemListeners() | Returns an array of all the item listeners registered on this choice. |
<T extends EventListener> | getListeners(Class<T> listenerType) | Returns an array of all the objects currently registered as |
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 |
protected void | processEvent(AWTEvent e) | Processes events on this choice. |
protected void | processItemEvent(ItemEvent e) | Processes item events occurring on this |
void | remove(int position) | Removes an item from the choice menu at the specified position. |
void | remove(String item) | Removes the first occurrence of |
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 |
void | select(int pos) | Sets the selected item in this |
void | select(String str) | Sets the selected item in this |
Methods declared in 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, 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, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, requestFocusInWindow, reshape, resize, resize, revalidate, setBackground, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setEnabled, setFocusable, setFocusTraversalKeys, setFocusTraversalKeysEnabled, setFont, setForeground, setIgnoreRepaint, setLocale, setLocation, setLocation, setMaximumSize, setMinimumSize, setMixingCutoutShape, setName, setPreferredSize, setSize, setSize, setVisible, show, show, size, toString, transferFocus, transferFocusBackward, transferFocusUpCycle, update, validate
Methods declared in 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 classComponent
- See Also:
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:
- 1.1
- See Also:
getItem(int)
countItems
@Deprecated public int countItems()
getItemCount()
.Returns the number of items in this Choice
menu.
- Returns:
- the number of items in this
Choice
menu
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 - Returns:
- the item at the specified index
- 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 isnull
- Since:
- 1.1
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 tonull
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 thisChoice
menu - Throws:
-
IllegalArgumentException
- if the item doesn't exist in the choice menu - Since:
- 1.1
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:
- 1.1
removeAll
public void removeAll()
Removes all items from the choice menu.
- Since:
- 1.1
- 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 interfaceItemSelectable
- Returns:
- the list of selected objects, or
null
- 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 position 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 interfaceItemSelectable
- Parameters:
-
l
- the item listener - Since:
- 1.1
- 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 interfaceItemSelectable
- Parameters:
-
l
- the item listener - Since:
- 1.1
- 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
ItemListener
s 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 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.
- Overrides:
-
getListeners
in classComponent
- Type Parameters:
-
T
- the type of the listeners - Parameters:
-
listenerType
- the type of listeners requested; this parameter should specify an interface that descends fromjava.util.EventListener
- Returns:
- an array of all objects registered as
FooListener
s on this choice, or an empty array if no such listeners have been added - Throws:
-
ClassCastException
- iflistenerType
doesn't specify a class or interface that implementsjava.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 classComponent
- Parameters:
-
e
- the event - Since:
- 1.1
- 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 viaaddItemListener
. - 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:
- 1.1
- 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 classComponent
- 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 interfaceAccessible
- Overrides:
-
getAccessibleContext
in classComponent
- Returns:
- an
AccessibleAWTChoice
that serves as theAccessibleContext
of thisChoice
- Since:
- 1.3