ImageObserver
, ItemSelectable
, MenuContainer
, Serializable
, Accessible
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.
Nested Classes
protected class
This class implements accessibility support for the List
class.
Constructors
Creates a new scrolling list.
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.
void
Adds the specified item to the end of scrolling list.
void
Adds the specified item to the scrolling list at the position indicated by the index.
void
Adds the specified action listener to receive action events from this list.
void
void
void
Adds the specified item listener to receive item events from this list.
void
Creates the peer for the list.
boolean
void
int
void
void
void
Deselects the item at the specified index.
Gets the AccessibleContext
associated with this List
.
Returns an array of all the action listeners registered on this list.
Gets the item associated with the specified index.
int
Gets the number of items in the list.
Returns an array of all the item listeners registered on this list.
Gets the items in the list.
Returns an array of all the objects currently registered as FooListener
s upon this List
.
Determines the minimum size of this scrolling list.
Gets the minimum dimensions for a list with the specified number of rows.
Gets the preferred size of this scrolling list.
Gets the preferred dimensions for a list with the specified number of rows.
int
Gets the number of visible lines in this list.
int
Gets the index of the selected item on the list,
int[]
Gets the selected indexes on the list.
Gets the selected item on this scrolling list.
Gets the selected items on this scrolling list.
Gets the selected items on this scrolling list in an array of Objects.
int
Gets the index of the item that was last made visible by the method makeVisible
.
boolean
Determines if the specified item in this scrolling list is selected.
boolean
Determines whether this list allows multiple selections.
boolean
void
Makes the item at the specified index visible.
Returns the parameter string representing the state of this scrolling list.
protected void
Processes action events occurring on this component by dispatching them to any registered ActionListener
objects.
protected void
Processes events on this scrolling list.
protected void
Processes item events occurring on this list by dispatching them to any registered ItemListener
objects.
void
Removes the item at the specified position from this scrolling list.
void
Removes the first occurrence of an item from the list.
void
Removes the specified action listener so that it no longer receives action events from this list.
void
Removes all items from this list.
void
Removes the specified item listener so that it no longer receives item events from this list.
void
Removes the peer for this list.
void
Replaces the item at the specified index in the scrolling list with the new string.
void
Selects the item at the specified index in the scrolling list.
void
Sets the flag that determines whether this list allows multiple selections.
void
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, getMouseListeners, getMouseMotionListeners, getMousePosition, getMouseWheelListeners, getName, getParent, 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, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paint, paintAll, postEvent, prepareImage, prepareImage, print, printAll, processComponentEvent, processFocusEvent, processHierarchyBoundsEvent, processHierarchyEvent, processInputMethodEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, processMouseWheelEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, 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
Creates a new scrolling list. By default, there are four visible lines and multiple selections are not allowed. Note that this is a convenience method for 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.
Creates a new scrolling list initialized with the specified number of visible lines. By default, multiple selections are not allowed. Note that this is a convenience method for 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.
Creates a new scrolling list initialized to display the specified number of rows. Note that if zero rows are specified, then the list will be created with a default of four rows. Also note that the number of visible rows in the list cannot be changed after it has been created. If the value of 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.
public void addNotify()
Creates the peer for the list. The peer allows us to modify the list's appearance without changing its functionality.
public void removeNotify()
Removes the peer for this list. The peer allows us to modify the list's appearance without changing its functionality.
removeNotify
in class Component
public int getItemCount()
Gets the number of items in the list.
Returns the number of items in the list.
Gets the item associated with the specified index.
index
- the position of the item
Gets the items in the list.
Adds the specified item to the end of scrolling list.
item
- the item to be added
Adds the specified item to the end of the list.
item
- the item to be added
Adds the specified item to the scrolling list at the position indicated by the index. The index is zero-based. If the value of the index is less than zero, or if the value of the index is greater than or equal to the number of items in the list, then the item is added to the end of the list.
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
Adds the specified item to the list at the position indicated by the index.
item
- the item to be added
index
- the position at which to add the item
Replaces the item at the specified index in the scrolling list with the new string.
newValue
- a new string to replace an existing item
index
- the position of the item to replace
ArrayIndexOutOfBoundsException
- if index
is out of range
public void removeAll()
Removes all items from this list.
Removes the first occurrence of an item from the list. If the specified item is selected, and is the only selected item in the list, the list is set to have no selection.
item
- the item to remove from the list
IllegalArgumentException
- if the item doesn't exist in the list
public void remove(int position)
Removes the item at the specified position from this scrolling list. If the item with the specified position is selected, and is the only selected item in the list, the list is set to have no selection.
position
- the index of the item to delete
ArrayIndexOutOfBoundsException
- if the position
is less than 0 or greater than getItemCount()-1
Removes the item at the specified position.
position
- the index of the item to delete
public int getSelectedIndex()
Gets the index of the selected item on the list,
-1
is returned.
public int[] getSelectedIndexes()
Gets the selected indexes on the list.
()
Gets the selected item on this scrolling list.
null
is returned.
()
Gets the selected items on this scrolling list.
()
Gets the selected items on this scrolling list in an array of Objects.
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.
public void select(int index)
Selects the item at the specified index in the scrolling list.
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 select
public void deselect(int index)
Deselects the item at the specified 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 deselect
public boolean isIndexSelected(int index)
Determines if the specified item in this scrolling list is selected.
index
- the item to be checked
true
if the specified item has been selected; false
otherwise
Determines if the specified item in the list is selected.
index
- specifies the item to be checked
true
if the item is selected; otherwise false
public int getRows()
Gets the number of visible lines in this list. Note that once the List
has been created, this number will never change.
public boolean isMultipleMode()
Determines whether this list allows multiple selections.
true
if this list allows multiple selections; otherwise, false
Determines whether this list allows multiple selections.
true
if this list allows multiple selections; otherwise false
public void setMultipleMode(boolean b)
Sets the flag that determines whether this list allows multiple selections. When the selection mode is changed from multiple-selection to single-selection, the selected items change as follows: If a selected item has the location cursor, only that item will remain selected. If no selected item has the location cursor, all items will be deselected.
b
- if true
then multiple selections are allowed; otherwise, only one item from the list can be selected at once
Enables or disables multiple selection mode for this list.
b
- true
to enable multiple mode, false
otherwise
public int getVisibleIndex()
Gets the index of the item that was last made visible by the method makeVisible
.
public void makeVisible(int index)
Makes the item at the specified index visible.
index
- the position of the item
Gets the preferred dimensions for a list with the specified number of rows.
rows
- number of rows in the list
Returns the preferred size of this component assuming it has the specified number of rows.
rows
- the number of rows
Gets the preferred size of this scrolling list.
getPreferredSize
in class Component
Returns the component's preferred size.
preferredSize
in class Component
Gets the minimum dimensions for a list with the specified number of rows.
rows
- number of rows in the list
Returns the minimum dimensions for the list with the specified number of rows.
rows
- the number of rows in the list
Determines the minimum size of this scrolling list.
getMinimumSize
in class Component
Returns the minimum size of this component.
minimumSize
in class Component
Adds the specified item listener to receive item events from this list. Item events are sent in response to user input, but not in response to calls to
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 listener
Removes the specified item listener so that it no longer receives item events from this list. 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.
removeItemListener
in interface ItemSelectable
l
- the item listener
Returns an array of all the item listeners registered on this list.
ItemListener
s or an empty array if no item listeners are currently registered
Adds the specified action listener to receive action events from this list. Action events occur when a user double-clicks on a list item or types Enter when the list has the keyboard focus.
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 listener
Removes the specified action listener so that it no longer receives action events from this list. Action events occur when a user double-clicks on a list item. 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 listener
Returns an array of all the action listeners registered on this list.
ActionListener
s or an empty array if no action listeners are currently registered
Returns an array of all the objects currently registered as
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
T
- the type of the listeners
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
Processes events on this scrolling list. If an event is an instance of
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 event
Processes item events occurring on this list 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:
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 event
Processes action events occurring on this component by dispatching them to any registered
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 event
()
Returns the parameter string representing the state of this scrolling list. This string is useful for debugging.
paramString
in class Component
Deletes the list items in the specified index range.
start
- the beginning index of the range to delete
end
- the ending index of the range to delete
Gets the 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
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