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Java™ Platform Standard Ed. 6 |
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java.lang.Object java.awt.Component java.awt.List
public class List
The List
component presents the user with a
scrolling list of text items. The list can be set up so that
the user can choose either one item or multiple items.
For example, the code . . .
List lst = new List(4, false); lst.add("Mercury"); lst.add("Venus"); lst.add("Earth"); lst.add("JavaSoft"); lst.add("Mars"); lst.add("Jupiter"); lst.add("Saturn"); lst.add("Uranus"); lst.add("Neptune"); lst.add("Pluto"); cnt.add(lst);
where cnt
is a container, produces the following
scrolling list:
If the List allows multiple selections, then clicking on
an item that is already selected deselects it. In the preceding
example, only one item from the scrolling list can be selected
at a time, since the second argument when creating the new scrolling
list is false
. If the List does not allow multiple
selections, selecting an item causes any other selected item
to be deselected.
Note that the list in the example shown was created with four visible
rows. Once the list has been created, the number of visible rows
cannot be changed. A default List
is created with
four rows, so that lst = new List()
is equivalent to
list = new List(4, false)
.
Beginning with Java 1.1, the Abstract Window Toolkit
sends the List
object all mouse, keyboard, and focus events
that occur over it. (The old AWT event model is being maintained
only for backwards compatibility, and its use is discouraged.)
When an item is selected or deselected by the user, AWT sends an instance
of ItemEvent
to the list.
When the user double-clicks on an item in a scrolling list,
AWT sends an instance of ActionEvent
to the
list following the item event. AWT also generates an action event
when the user presses the return key while an item in the
list is selected.
If an application wants to perform some action based on an item
in this list being selected or activated by the user, it should implement
ItemListener
or ActionListener
as appropriate and register the new listener to receive
events from this list.
For multiple-selection scrolling lists, it is considered a better user interface to use an external gesture (such as clicking on a button) to trigger the action.
ItemEvent
,
ItemListener
,
ActionEvent
,
ActionListener
,
Serialized FormNested Class Summary | |
---|---|
protected class |
List.AccessibleAWTList
This class implements accessibility support for the List 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 | |
---|---|
List()
Creates a new scrolling list. |
|
List(int rows)
Creates a new scrolling list initialized with the specified number of visible lines. |
|
List(int rows,
boolean multipleMode)
Creates a new scrolling list initialized to display the specified number of rows. |
Method Summary | ||
---|---|---|
void |
add(String item)
Adds the specified item to the end of scrolling list. |
|
void |
add(String item,
int index)
Adds the specified item to the the scrolling list at the position indicated by the index. |
|
void |
addActionListener(ActionListener l)
Adds the specified action listener to receive action events from this list. |
|
void |
addItem(String item)
Deprecated. replaced by add(String) . |
|
void |
addItem(String item,
int index)
Deprecated. replaced by add(String, int) . |
|
void |
addItemListener(ItemListener l)
Adds the specified item listener to receive item events from this list. |
|
void |
addNotify()
Creates the peer for the list. |
|
boolean |
allowsMultipleSelections()
Deprecated. As of JDK version 1.1, replaced by isMultipleMode() . |
|
void |
clear()
Deprecated. As of JDK version 1.1, replaced by removeAll() . |
|
int |
countItems()
Deprecated. As of JDK version 1.1, replaced by getItemCount() . |
|
void |
delItem(int position)
Deprecated. replaced by remove(String)
and remove(int) . |
|
void |
delItems(int start,
int end)
Deprecated. As of JDK version 1.1, Not for public use in the future. This method is expected to be retained only as a package private method. |
|
void |
deselect(int index)
Deselects the item at the specified index. |
|
AccessibleContext |
getAccessibleContext()
Gets the AccessibleContext associated with this
List . |
|
ActionListener[] |
getActionListeners()
Returns an array of all the action listeners registered on this list. |
|
String |
getItem(int index)
Gets the item associated with the specified index. |
|
int |
getItemCount()
Gets the number of items in the list. |
|
ItemListener[] |
getItemListeners()
Returns an array of all the item listeners registered on this list. |
|
String[] |
getItems()
Gets the items in the list. |
|
|
getListeners(Class<T> listenerType)
Returns an array of all the objects currently registered as FooListener s
upon this List . |
|
Dimension |
getMinimumSize()
Determines the minimum size of this scrolling list. |
|
Dimension |
getMinimumSize(int rows)
Gets the minumum dimensions for a list with the specified number of rows. |
|
Dimension |
getPreferredSize()
Gets the preferred size of this scrolling list. |
|
Dimension |
getPreferredSize(int rows)
Gets the preferred dimensions for a list with the specified number of rows. |
|
int |
getRows()
Gets the number of visible lines in this list. |
|
int |
getSelectedIndex()
Gets the index of the selected item on the list, |
|
int[] |
getSelectedIndexes()
Gets the selected indexes on the list. |
|
String |
getSelectedItem()
Gets the selected item on this scrolling list. |
|
String[] |
getSelectedItems()
Gets the selected items on this scrolling list. |
|
Object[] |
getSelectedObjects()
Gets the selected items on this scrolling list in an array of Objects. |
|
int |
getVisibleIndex()
Gets the index of the item that was last made visible by the method makeVisible . |
|
boolean |
isIndexSelected(int index)
Determines if the specified item in this scrolling list is selected. |
|
boolean |
isMultipleMode()
Determines whether this list allows multiple selections. |
|
boolean |
isSelected(int index)
Deprecated. As of JDK version 1.1, replaced by isIndexSelected(int) . |
|
void |
makeVisible(int index)
Makes the item at the specified index visible. |
|
Dimension |
minimumSize()
Deprecated. As of JDK version 1.1, replaced by getMinimumSize() . |
|
Dimension |
minimumSize(int rows)
Deprecated. As of JDK version 1.1, replaced by getMinimumSize(int) . |
|
protected String |
paramString()
Returns the parameter string representing the state of this scrolling list. |
|
Dimension |
preferredSize()
Deprecated. As of JDK version 1.1, replaced by getPreferredSize() . |
|
Dimension |
preferredSize(int rows)
Deprecated. As of JDK version 1.1, replaced by getPreferredSize(int) . |
|
protected void |
processActionEvent(ActionEvent e)
Processes action events occurring on this component by dispatching them to any registered ActionListener objects. |
|
protected void |
processEvent(AWTEvent e)
Processes events on this scrolling list. |
|
protected void |
processItemEvent(ItemEvent e)
Processes item events occurring on this list by dispatching them to any registered ItemListener objects. |
|
void |
remove(int position)
Removes the item at the specified position from this scrolling list. |
|
void |
remove(String item)
Removes the first occurrence of an item from the list. |
|
void |
removeActionListener(ActionListener l)
Removes the specified action listener so that it no longer receives action events from this list. |
|
void |
removeAll()
Removes all items from this list. |
|
void |
removeItemListener(ItemListener l)
Removes the specified item listener so that it no longer receives item events from this list. |
|
void |
removeNotify()
Removes the peer for this list. |
|
void |
replaceItem(String newValue,
int index)
Replaces the item at the specified index in the scrolling list with the new string. |
|
void |
select(int index)
Selects the item at the specified index in the scrolling list. |
|
void |
setMultipleMode(boolean b)
Sets the flag that determines whether this list allows multiple selections. |
|
void |
setMultipleSelections(boolean b)
Deprecated. As of JDK version 1.1, replaced by setMultipleMode(boolean) . |
Methods inherited from class java.lang.Object |
---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Constructor Detail |
---|
public List() throws HeadlessException
List(0, false)
. Also note that the number of visible
lines in the list cannot be changed after it has been created.
HeadlessException
- if GraphicsEnvironment.isHeadless()
returns true.GraphicsEnvironment.isHeadless()
public List(int rows) throws HeadlessException
List(rows, false)
. Also note that the number
of visible rows in the list cannot be changed after it has
been created.
rows
- the number of items to show.
HeadlessException
- if GraphicsEnvironment.isHeadless()
returns true.GraphicsEnvironment.isHeadless()
public List(int rows, boolean multipleMode) throws HeadlessException
multipleMode
is
true
, then the user can select multiple items from
the list. If it is false
, only one item at a time
can be selected.
rows
- the number of items to show.multipleMode
- if true
,
then multiple selections are allowed;
otherwise, only one item can be selected at a time.
HeadlessException
- if GraphicsEnvironment.isHeadless()
returns true.GraphicsEnvironment.isHeadless()
Method Detail |
---|
public void addNotify()
addNotify
in class Component
Component.isDisplayable()
,
Component.removeNotify()
public void removeNotify()
removeNotify
in class Component
Component.isDisplayable()
,
Component.addNotify()
public int getItemCount()
getItem(int)
@Deprecated public int countItems()
getItemCount()
.
public String getItem(int index)
index
- the position of the item
getItemCount()
public String[] getItems()
select(int)
,
deselect(int)
,
isIndexSelected(int)
public void add(String item)
item
- the item to be added@Deprecated public void addItem(String item)
add(String)
.
public void add(String item, int index)
item
- the item to be added;
if this parameter is null
then the item is
treated as an empty string, ""
index
- the position at which to add the item@Deprecated public void addItem(String item, int index)
add(String, int)
.
public void replaceItem(String newValue, int index)
newValue
- a new string to replace an existing itemindex
- the position of the item to replace
ArrayIndexOutOfBoundsException
- if index
is out of rangepublic void removeAll()
remove(java.lang.String)
,
delItems(int, int)
@Deprecated public void clear()
removeAll()
.
public void remove(String item)
item
- the item to remove from the list
IllegalArgumentException
- if the item doesn't exist in the listpublic void remove(int position)
position
- the index of the item to delete
ArrayIndexOutOfBoundsException
- if the position
is less than 0 or
greater than getItemCount()-1
add(String, int)
@Deprecated public void delItem(int position)
remove(String)
and remove(int)
.
public int getSelectedIndex()
-1
is returned.select(int)
,
deselect(int)
,
isIndexSelected(int)
public int[] getSelectedIndexes()
select(int)
,
deselect(int)
,
isIndexSelected(int)
public String getSelectedItem()
null
is returned.select(int)
,
deselect(int)
,
isIndexSelected(int)
public String[] getSelectedItems()
select(int)
,
deselect(int)
,
isIndexSelected(int)
public Object[] getSelectedObjects()
getSelectedObjects
in interface ItemSelectable
Object
s representing the
selected items on this scrolling list;
if no item is selected, a zero-length array is returned.getSelectedItems()
,
ItemSelectable
public void select(int index)
Note that passing out of range parameters is invalid, and will result in unspecified behavior.
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.
index
- the position of the item to selectgetSelectedItem()
,
deselect(int)
,
isIndexSelected(int)
public void deselect(int index)
Note that passing out of range parameters is invalid, and will result in unspecified behavior.
If the item at the specified index is not selected, then the operation is ignored.
index
- the position of the item to deselectselect(int)
,
getSelectedItem()
,
isIndexSelected(int)
public boolean isIndexSelected(int index)
index
- the item to be checked
true
if the specified item has been
selected; false
otherwiseselect(int)
,
deselect(int)
@Deprecated public boolean isSelected(int index)
isIndexSelected(int)
.
public int getRows()
List
has been created, this number
will never change.
public boolean isMultipleMode()
true
if this list allows multiple
selections; otherwise, false
setMultipleMode(boolean)
@Deprecated public boolean allowsMultipleSelections()
isMultipleMode()
.
public void setMultipleMode(boolean b)
b
- if true
then multiple selections
are allowed; otherwise, only one item from
the list can be selected at onceisMultipleMode()
@Deprecated public void setMultipleSelections(boolean b)
setMultipleMode(boolean)
.
public int getVisibleIndex()
makeVisible
.
makeVisible(int)
public void makeVisible(int index)
index
- the position of the itemgetVisibleIndex()
public Dimension getPreferredSize(int rows)
rows
- number of rows in the list
Component.getPreferredSize()
@Deprecated public Dimension preferredSize(int rows)
getPreferredSize(int)
.
public Dimension getPreferredSize()
getPreferredSize
in class Component
Component.getPreferredSize()
@Deprecated public Dimension preferredSize()
getPreferredSize()
.
preferredSize
in class Component
public Dimension getMinimumSize(int rows)
rows
- number of rows in the list
Component.getMinimumSize()
@Deprecated public Dimension minimumSize(int rows)
getMinimumSize(int)
.
public Dimension getMinimumSize()
getMinimumSize
in class Component
Component.getMinimumSize()
@Deprecated public Dimension minimumSize()
getMinimumSize()
.
minimumSize
in class Component
public void addItemListener(ItemListener l)
select
or deselect
.
If listener l
is null
,
no exception is thrown and no action is performed.
Refer to AWT Threading Issues for details on AWT's threading model.
addItemListener
in interface ItemSelectable
l
- the item listenerremoveItemListener(java.awt.event.ItemListener)
,
getItemListeners()
,
select(int)
,
deselect(int)
,
ItemEvent
,
ItemListener
public void removeItemListener(ItemListener l)
l
is null
,
no exception is thrown and no action is performed.
Refer to AWT Threading Issues for details on AWT's threading model.
removeItemListener
in interface ItemSelectable
l
- the item listeneraddItemListener(java.awt.event.ItemListener)
,
getItemListeners()
,
ItemEvent
,
ItemListener
public ItemListener[] getItemListeners()
ItemListener
s
or an empty array if no item
listeners are currently registeredaddItemListener(java.awt.event.ItemListener)
,
removeItemListener(java.awt.event.ItemListener)
,
ItemEvent
,
ItemListener
public void addActionListener(ActionListener l)
If listener 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 action listenerremoveActionListener(java.awt.event.ActionListener)
,
getActionListeners()
,
ActionEvent
,
ActionListener
public void removeActionListener(ActionListener l)
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 action listeneraddActionListener(java.awt.event.ActionListener)
,
getActionListeners()
,
ActionEvent
,
ActionListener
public ActionListener[] getActionListeners()
ActionListener
s
or an empty array if no action
listeners are currently registeredaddActionListener(java.awt.event.ActionListener)
,
removeActionListener(java.awt.event.ActionListener)
,
ActionEvent
,
ActionListener
public <T extends EventListener> T[] getListeners(Class<T> listenerType)
FooListener
s
upon this List
.
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
List
l
for its item listeners with the following code:
ItemListener[] ils = (ItemListener[])(l.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 list,
or an empty array if no such
listeners have been added
ClassCastException
- if listenerType
doesn't specify a class or interface that implements
java.util.EventListener
getItemListeners()
protected void processEvent(AWTEvent e)
ItemEvent
, it invokes the
processItemEvent
method. Else, if the
event is an instance of ActionEvent
,
it invokes processActionEvent
.
If the event is not an item event or an action event,
it invokes processEvent
on the superclass.
Note that if the event parameter is null
the behavior is unspecified and may result in an
exception.
processEvent
in class Component
e
- the eventActionEvent
,
ItemEvent
,
processActionEvent(java.awt.event.ActionEvent)
,
processItemEvent(java.awt.event.ItemEvent)
protected void processItemEvent(ItemEvent e)
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 eventItemEvent
,
ItemListener
,
addItemListener(java.awt.event.ItemListener)
,
Component.enableEvents(long)
protected void processActionEvent(ActionEvent e)
ActionListener
objects.
This method is not called unless action events are enabled for this component. Action events are enabled when one of the following occurs:
ActionListener
object is registered
via addActionListener
.
enableEvents
.
Note that if the event parameter is null
the behavior is unspecified and may result in an
exception.
e
- the action eventActionEvent
,
ActionListener
,
addActionListener(java.awt.event.ActionListener)
,
Component.enableEvents(long)
protected String paramString()
paramString
in class Component
@Deprecated public void delItems(int start, int end)
public AccessibleContext getAccessibleContext()
AccessibleContext
associated with this
List
. For lists, the AccessibleContext
takes the form of an AccessibleAWTList
.
A new AccessibleAWTList
instance is created, if necessary.
getAccessibleContext
in interface Accessible
getAccessibleContext
in class Component
AccessibleAWTList
that serves as the
AccessibleContext
of this List
|
Java™ Platform Standard Ed. 6 |
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