How to use list

1
How to use list

• A JList presents the user with a group of items,
  displayed in one or more columns, to choose from.
  
• Lists can have many items, so they are often put
  in scroll panes.
• ConstructorsJList(Object) // immutable
  JList(Vector) // immutable JList()
  // mutable
• JList(ListModel) // mutable

2
How to Use Models

• Provides flexibility in determining how data is
  stored and retrieved.
• Most Swing components have models.
• JButton has a ButtonModel object that stores the
  button's state
• what its keyboard mnemonic is,
• whether it's enabled, selected, or pressed, etc
• Some components have multiple models.
• A JList has
• a ListModel object to hold the list's contents
• a ListSelectionModel object to track the list's
  current selection.

3
ListModel

• They give you flexibility in determining how data
  is stored and retrieved.

ListModel
AbstractListModel
DefaultListModel
4
(No Transcript)
5
String choices "A", "long", "array", "of",
"strings" list new JList(choice)
list.setSelectionMode(ListSelectionModel.SINGLE_I
NTERVAL_SELECTION) list.setLayoutOrientation(JLis
t.HORIZONTAL_WRAP) JScrollPane listScroller
new JScrollPane(list) listScroller.setPreferredSi
ze(new Dimension(250, 80))
6
SINGLE_SELECTION
SINGLE_INTERVAL_SELECTION
MULTIPLE_INTERVAL_SELECTION 
7
HORIZONTAL_WRAP
VERTICAL_WRAP
VERTICAL
8
ListSelectionEvent and ListSelectionListener

• List selection events occur when
• the selection in a list or table is either
  changing or has just changed.
• List selection events are fired from an object
  that implements the ListSelectionModel interface.
  
• To detect list selection events, you register a
  listener on the appropriate list selection model
  object.
• The JList class also gives you the option of
  registering a listener on the list itself.

9
The ListSelectionListener Interface

• valueChanged(ListSelectionEvent e)
• Called in response to selection changes.

10
The ListSelectionEvent API

• Object getSource()(in java.util.EventObject)
  Return the object that fired the event.
• int getFirstIndex()
• Return the index of the first item whose
  selection value has changed.
• int getLastIndex()
• Return the index of the last item whose
  selection value has changed.
• boolean getValueIsAdjusting()
• Return true if the selection is still
  changing.

11

• // Fig. 11.23 ListFrame.java
• // Selecting colors from a JList.
• import java.awt.FlowLayout
• import java.awt.Color
• import javax.swing.JFrame
• import javax.swing.JList
• import javax.swing.JScrollPane
• import javax.swing.event.ListSelectionListener
• import javax.swing.event.ListSelectionEvent
• import javax.swing.ListSelectionModel
• public class ListFrame extends JFrame
• private JList colorJList // list to display
  colors
• private final String colorNames "Black",
  "Blue", "Cyan",
• "Dark Gray", "Gray", "Green", "Light Gray",
  "Magenta",
• "Orange", "Pink", "Red", "White", "Yellow"
  
• private final Color colors Color.BLACK,
  Color.BLUE, Color.CYAN,
• Color.DARK_GRAY, Color.GRAY, Color.GREEN,
  Color.LIGHT_GRAY,

12
ListSelectionModel listSelectionModel
listSelectionModel colorJList.getSelectionModel
() listSelectionModel.addListSelectionListener(
new ListSelectionListener()
public void valueChanged( ListSelectionEvent
event ) .
// end method valueChanged //
end anonymous inner class ) // end call to
addListSelectionListener

• // ListFrame constructor add JScrollPane
  containing JList to JFrame
• public ListFrame()
• super( "List Test" )
• setLayout( new FlowLayout() ) // set frame
  layout
• colorJList new JList( colorNames ) //
  create with colorNames
• colorJList.setVisibleRowCount( 5 ) //
  display five rows at once
• // do not allow multiple selections
• colorJList.setSelectionMode(
  ListSelectionModel.SINGLE_SELECTION )
• // add a JScrollPane containing JList to
  frame
• add( new JScrollPane( colorJList ) )
• colorJList.addListSelectionListener(
• new ListSelectionListener() // anonymous
  inner class
• // handle list selection events

13

• // Fig. 11.25 MultipleSelectionFrame.java
• // Copying items from one List to another.
• import java.awt.FlowLayout
• import java.awt.event.ActionListener
• import java.awt.event.ActionEvent
• import javax.swing.JFrame
• import javax.swing.JList
• import javax.swing.JButton
• import javax.swing.JScrollPane
• import javax.swing.ListSelectionModel
• public class MultipleSelectionFrame extends
  JFrame
• private JList colorJList // list to hold
  color names
• private JList copyJList // list to copy color
  names into
• private JButton copyJButton // button to copy
  selected names
• private final String colorNames "Black",
  "Blue", "Cyan",
• "Dark Gray", "Gray", "Green", "Light Gray",
  "Magenta", "Orange",
• "Pink", "Red", "White", "Yellow"

14

• // MultipleSelectionFrame constructor
• public MultipleSelectionFrame()
• super( "Multiple Selection Lists" )
• setLayout( new FlowLayout() ) // set frame
  layout
• colorJList new JList( colorNames ) //
  holds names of all colors
• colorJList.setVisibleRowCount( 5 ) // show
  five rows
• colorJList.setSelectionMode(
• ListSelectionModel.MULTIPLE_INTERVAL_SELE
  CTION )
• add( new JScrollPane( colorJList ) ) //
  add list with scrollpane
• copyJButton new JButton( "Copy gtgtgt" ) //
  create copy button
• copyJButton.addActionListener(
• new ActionListener() // anonymous inner
  class
• // handle button event
• public void actionPerformed(
  ActionEvent event )

15

• add( copyJButton ) // add copy button to
  JFrame
• copyJList new JList() // create list to
  hold copied color names
• copyJList.setVisibleRowCount( 5 ) // show
  5 rows
• copyJList.setFixedCellWidth( 100 ) // set
  width
• copyJList.setFixedCellHeight( 15 ) // set
  height
• copyJList.setSelectionMode(
• ListSelectionModel.SINGLE_INTERVAL_SELECT
  ION )
• add( new JScrollPane( copyJList ) ) // add
  list with scrollpane
• // end MultipleSelectionFrame constructor
• // end class MultipleSelectionFrame

16
ListDataEvent and ListDataListener

• List data events occur when the contents of a
  mutable list change.
• List data events are fired from an object that
  implements the ListModel interface. Therefore you
  have to register a list data listener with the
  list model object.

17

• DefaultListModel listModel new
  DefaultListModel()
• listModel.addElement("Whistler, Canada")
• listModel.addElement("Jackson Hole, Wyoming")
• listModel.addElement("Squaw Valley,
  California")
• JList list new JList(listModel) //
  JList(ListModel)
• listModel.addListDataListener(
• new ListDataListener()
• // implementation of ListDataListener methods
• )

18
ListDataListener Interface

• intervalAdded(ListDataEvent)
• Called when one or more items have been added to
  the list.
• intervalRemoved(ListDataEvent)
• Called when one or more items have been removed
  from the list.
• contentsChanged(ListDataEvent)
• Called when the contents of one or more items in
  the list have changed.

19
ListDataEvent API

• Object getSource()Return the object that fired
  the event.
• int getIndex0()
• Return the index of the first item whose value
  has changed.
• int getIndex1()
• Return the index of the last item whose value
  has changed.
• int getType()
• Return the event type. The possible values are
  CONTENTS_CHANGED, INTERVAL_ADDED, or
  INTERVAL_REMOVED.