Choice (Java 2 Platform SE 5.0) (original) (raw)

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

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](../../java/awt/HeadlessException.html "class in java.awt") - if GraphicsEnvironment.isHeadless() returns true

See Also:

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

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](../../java/awt/Component.html#addNotify%28%29) in class [Component](../../java/awt/Component.html "class in java.awt")

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 thisChoice 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](../../java/lang/NullPointerException.html "class in java.lang") - if the item's value isnull

Since:

JDK1.1

addItem

public void addItem(String item)

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

Adds an item to this Choice menu.

Parameters:

item - the item to be added

Throws:

[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang") - 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 toindex 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](../../java/lang/IllegalArgumentException.html "class in java.lang") - 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](../../java/lang/IllegalArgumentException.html "class in java.lang") - 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

Parameters:

position - the position of the item

Throws:

[IndexOutOfBoundsException](../../java/lang/IndexOutOfBoundsException.html "class in java.lang") - 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](../../java/awt/ItemSelectable.html#getSelectedObjects%28%29) in interface [ItemSelectable](../../java/awt/ItemSelectable.html "interface in java.awt")

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 anItemEvent is by user interaction.

Parameters:

pos - the positon of the selected item

Throws:

[IllegalArgumentException](../../java/lang/IllegalArgumentException.html "class in java.lang") - 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 anItemEvent 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.

Specified by:

[addItemListener](../../java/awt/ItemSelectable.html#addItemListener%28java.awt.event.ItemListener%29) in interface [ItemSelectable](../../java/awt/ItemSelectable.html "interface in java.awt")

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.

Specified by:

[removeItemListener](../../java/awt/ItemSelectable.html#removeItemListener%28java.awt.event.ItemListener%29) in interface [ItemSelectable](../../java/awt/ItemSelectable.html "interface in java.awt")

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 listenerType)

Returns an array of all the objects currently registered as _Foo_Listeners upon this Choice._Foo_Listeners are registered using theadd_Foo_Listener method.

You can specify the listenerType argument with a class literal, such as_Foo_Listener.class. For example, you can query aChoice 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](../../java/awt/Component.html#getListeners%28java.lang.Class%29) in class [Component](../../java/awt/Component.html "class in java.awt")

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_Foo_Listeners on this choice, or an empty array if no such listeners have been added

Throws:

[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang") - if listenerType 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 theprocessItemEvent 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](../../java/awt/Component.html#processEvent%28java.awt.AWTEvent%29) in class [Component](../../java/awt/Component.html "class in java.awt")

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 registeredItemListener 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 benull.

Overrides:

[paramString](../../java/awt/Component.html#paramString%28%29) in class [Component](../../java/awt/Component.html "class in java.awt")

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](../../javax/accessibility/Accessible.html#getAccessibleContext%28%29) in interface [Accessible](../../javax/accessibility/Accessible.html "interface in javax.accessibility")

Overrides:

[getAccessibleContext](../../java/awt/Component.html#getAccessibleContext%28%29) in class [Component](../../java/awt/Component.html "class in java.awt")

Returns:

an AccessibleAWTChoice that serves as the AccessibleContext of this Choice

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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

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