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Java(TM) 2 Platform, Standard Edition, v1.2.2 API Specification: Class Choice - JDK 5 Documentation v1.2.2, Java 2 SDK 英文文档

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java.awt
Class Choice

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.Choice

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public class Choice

extends Component

implements ItemSelectable

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:

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 Choice ColorChooser = new Choice();
 ColorChooser.add("Green");
 ColorChooser.add("Red");
 ColorChooser.add("Blue");
 

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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.

Since:

JDK1.0

See Also:

Serialized Form

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Fields inherited from class java.awt.Component

BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT

 

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)           Adds an item to this Choice.
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().
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.
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 the parameter 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)           Remove 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, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addPropertyChangeListener, addPropertyChangeListener, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, deliverEvent, disable, disableEvents, dispatchEvent, doLayout, enable, enable, enableEvents, enableInputMethods, firePropertyChange, getAlignmentX, getAlignmentY, getBackground, getBounds, getBounds, getColorModel, getComponentAt, getComponentAt, getComponentOrientation, getCursor, getDropTarget, getFont, getFontMetrics, getForeground, getGraphics, getHeight, getInputContext, getInputMethodRequests, getLocale, getLocation, getLocation, getLocationOnScreen, getMaximumSize, getMinimumSize, getName, getParent, getPeer, getPreferredSize, getSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, invalidate, isDisplayable, isDoubleBuffered, isEnabled, isFocusTraversable, isLightweight, isOpaque, 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, processInputMethodEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, remove, removeComponentListener, removeFocusListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeNotify, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, reshape, resize, resize, setBackground, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setEnabled, setFont, setForeground, setLocale, setLocation, setLocation, setName, setSize, setSize, setVisible, show, show, size, toString, transferFocus, update, validate

 

Methods inherited from class java.lang.Object

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

 

Constructor Detail

Choice

public Choice()

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.

See Also:

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()

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getItemCount

public int getItemCount()

Returns the number of items in this Choice menu.

Since:

JDK1.1

See Also:

getItem(int)

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countItems

public int countItems()

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

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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()

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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

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addItem

public void addItem(String item)

Adds an item to this Choice.

Parameters:

item - the item to be added

Throws:

NullPointerException - If the item's value is equal to null.

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insert

public void insert(String item,
                   int index)

Inserts the item into this choice at the specified position.

Parameters:

item - the item to be inserted

index - the position at which the item should be inserted

Throws:

IllegalArgumentException - if index is less than 0.

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remove

public void remove(String item)

Remove the first occurrence of item from the Choice menu.

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

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remove

public void remove(int position)

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

Parameters:

position - the position of the item.

Since:

JDK1.1

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removeAll

public void removeAll()

Removes all items from the choice menu.

Since:

JDK1.1

See Also:

remove(java.lang.String)

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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()

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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

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getSelectedIndex

public int getSelectedIndex()

Returns the index of the currently selected item.

See Also:

getSelectedItem()

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select

public void select(int pos)

Sets the selected item in this Choice menu to be the item at the specified position.

Parameters:

pos - the positon of the selected item.

Throws:

IllegalArgumentException - if the specified position is invalid.

See Also:

getSelectedItem(), getSelectedIndex()

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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.

Parameters:

str - the specified string

See Also:

getSelectedItem(), getSelectedIndex()

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addItemListener

public void addItemListener(ItemListener l)

Adds the specified item listener to receive item events from this Choice menu. If l is null, no exception is thrown and no action is performed.

Specified by:

addItemListener in interface ItemSelectable

Parameters:

l - the item listener.

Since:

JDK1.1

See Also:

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

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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.

Specified by:

removeItemListener in interface ItemSelectable

Parameters:

l - the item listener.

Since:

JDK1.1

See Also:

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

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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.

Overrides:

processEvent in class Component

Parameters:

e - the event.

Since:

JDK1.1

See Also:

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

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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.

Parameters:

e - the item event.

Since:

JDK1.1

See Also:

ItemEvent, ItemListener, addItemListener(java.awt.event.ItemListener), Component.enableEvents(long)

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paramString

protected String paramString()

Returns the parameter string representing the state of this choice menu. This string is useful for debugging.

Overrides:

paramString in class Component

Returns:

the parameter string of this Choice menu.

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