Creating User Interfaces

1
Creating User Interfaces

• JComponent
• JButton
• JLabel
• JTextField
• JTextArea
• JComboBox
• JList
• JCheckBox
• JRadioButton
• Dialogs

2
Component Properties

• The Component class is root for all UI
• components and containers.
• List of frequently used properties
• font
• background
• foreground
• preferredSize
• minimumSize
• maximumSize

3
JComponent Properties

• All but a few Swing components
• (such JFrame, JApplet and JDialog)
• are subclasses of JComponent.
• toolTipText
• doubleBuffered (to reduce flickering)
• border

4
Buttons
5
JButton

• A button is a component that triggers an Action
  Event when clicked.
• The following are JButton non-default
  constructors
• JButton(String text)
• JButton(String text, Icon icon)
• JButton(Icon icon)

6
JButton Properties

• mnemonic (to specify a shortcut key AltS)
• icon (image on the button)
• Position of text and icon on the button
• horizontalAlignment
• verticalAlignment
• horizontalTextPosition
• verticalTextPosition

7
JLabel

• A label is a display area for a short text, an
  image, or both.
• The non-default constructors for labels are as
  follows
• JLabel(String text, int horizontalAlignment)
• JLabel(String text)
• JLabel(Icon icon)
• JLabel(Icon icon, int horizontalAlignment)

8
JLabel Methods

• void setText(String str)
• String getText()
• void setAlignment(int how)
• SwingConstants.LEFT
• SwingConstants.CENTER
• SwingConstants.RIGHT
• int getAlignment()

9
JLabel Methods

• Example
• JLabel latLabel
• new JLabel(Latitude, SwingConstants.RIGHT)

10
JTextField

• A text field is an input area where the usercan
  type in characters. Text fields are usefulin
  that they enable the user to enter in variable
  data (such as a name or a description).

11
JTextField Constructors

• JTextField(int columns)
• Creates an empty text field with the specified
  number of columns.
• JTextField(String text)
• Creates a text field initialized with the
  specified text.
• JTextField(String text, int columns)
• Creates a text field initialized with
  thespecified text and the column size.

12
JTextField Properties

• text
• horizontalAlignment
• editable
• columns

http//www.cs.joensuu.fi/koles/utm/utm.html
13
JTextField Methods

• String getText()
• Returns the string from the text field.
• setText(String text)
• Puts the given string in the text field.
• void setEditable(boolean editable)
• Enables or disables the text field to be edited.
  By default, editable is true.
• void setColumns(int)
• Sets the number of columns in this text
  field.The length of the text field is
  changeable.

14
JTextField Example

• Create JTextField
• JTextField latTextField new JTextField("",
  30)
• panel.add(latTextField)
• . . .
• Use the JTextField
• String latString latTextField.getText()
• // double lat Double.parseDouble(latString)

15
JTextArea

• If you want to let the user enter multiple lines
  of text, you cannot use text fields unless you
  create several of them. The solution is to use
  JTextArea, which enables the user to enter
  multiple lines of text.

16
JTextArea Constructors

• JTextArea(int rows, int columns)
• Creates a text area with the specified number of
  rows and columns.
• JTextArea(String s, int rows, int columns)
• Creates a text area with the initial text
  andthe number of rows and columns specified.

17
JTextArea Properties

• text
• editable
• columns
• lineWrap
• wrapStyleWord
• rows
• lineCount
• tabSize

18
Example Using Text Area

• String text A text /n more text
• JTextArea jta new JTextArea()
• jta.setText(text)

19
JComboBox

• A combo box is a simple list of items from which
  the user can choose. It performs basically the
  same function as a list, but can get only one
  value. Also known as choice or drop-down menu
• To create a choice, use constructors
• JComboBox()
• JComboBox(Object stringItems)

20
JComboBox Methods

• To add an item to a JComboBox, use
• void addItem(Object item)
• To get an item from JComboBox, use
• Object getItem()

21
Using theitemStateChanged Handler

• JComboBox can generate ActionEvent and ItemEvent.
  
• When a choice is checked or unchecked,
  itemStateChanged() for ItemEvent is invoked as
  well as the actionPerformed() handler for
  ActionEvent.

22
Example JComboBox

• String itemStringItem 1, Item 2, Item
  3
• // Create JComboBox
• JComboBox jcbo new JComboBox(itemsString)
• // Register Listener
• jcbo.addItemListener(this)

public void itemStateChanged(ItemEvent e)
int i jcbo.getSelectedIndex() //do
something System.out.println(Index is
i) System.out.println(Item is
itemStringi)
23
JList

• A list is a component that performs basically the
  same function as a combo box, but it enables the
  user to choose a single value or multiple values.
  

24
JList Constructors

• JList()
• Creates an empty list.
• JList(Object stringItems)
• Creates a new list initialized with items.

25
JList Properties Methods

• selectedIndex
• selectedIndices
• selectedValue
• selectedValues
• selectionMode SINGLE_SELECTION,
• SINGLE_INTERVAL_SELECTION,
• MULTIPLE_INTERVAL_SELECTION.
• int getSelectedIndex()
• int getSelectedIndices()

26
JCheckBox

• A check box is a component that enables the user
  to toggle a choice on or off, like a light
  switch.

27
JCheckBox Constructors

• JCheckBox()
• JCheckBox(String text)
• JCheckBox(String text, boolean selected)
• JCheckBox(Icon icon)
• JCheckBox(String text, Icon icon)
• JCheckBox(String text, Icon icon, boolean
  selected)

28
JCheckBox Properties

• JCheckBox has all the properties in JButton.
• Additionally, JCheckBox has the following
  property
• selected

29
JCheckBox

• jchk1 new JCheckBox(Check 1, FALSE)
• jchk2 new JCheckBox(Check 2, TRUE)
• jchk1.addItemListener()
• jchk2.addItemListener()
• ...
• public void itemStateChanged(ItemEvent e)
• int i
• if(e.getSource() instanceof JCheckBox)
• if(jchk1.isSelected())
• // do something
• if(jchk2.isSelected())
• // do something else

30
JRadioButton

• Radio buttons are variations of check boxes.
• They are often used in the group, where only one
  button is checked at a time.

31
JRadioButton Constructors

• JRadioButton()
• JRadioButton(String text)
• JRadioButton(String text, boolean selected)
• JRadioButton(Icon icon)
• JRadioButton(String text, Icon icon)
• JRadioButton(String text, Icon icon, boolean
  selected)

32
JRadioButton Properties

• JRadioButton has all the properties in JButton.
• Additionally, JRadioButton has the following
  property
• selected
• Example
• JRadioButton jrb1 JRadioButton(Radio 1)
• JRadioButton jrb2 JRadioButton(Radio 2,
  selected)

33
Grouping Radio Buttons

• // Create JRadioButtons
• JRadioButton jrb1 JRadioButton(Radio 1)
• JRadioButton jrb2 JRadioButton(Radio 2,
  selected)
• // Create group of JRadioButtons
• ButtonGroup jrbg new ButtonGroup()
• jrbg.add(jrb1)
• jrbg.add(jrb2)

34
Message Dialogs

• A dialog is normally used as a temporary window
  to receive additional information from the user,
  or to provide notification that some event has
  occurred.

35
Creating Message Dialogs

• Use static method in JOptionPane class.
• showMessageDialog(
• Component parentComponent,
• Object message,
• String title,
• int messageType)
• showMessageDialog(
• Component parentComponent,
• Object message,
• String title,
• int messageType,
• Icon icon)

36
Dialogs
Example Message dialog with default title and
icon String str Eggs are not supposed to be
green. JOptionPane.showMessageDialog(frame,
str)

• http//java.sun.com/docs/books/tutorial/uiswing/co
  mponents/dialog.html

37
Examples

• String str Eggs are not supposed to be
  green.
• JOptionPane.showMessageDialog(frame, str,
• Message)
• JOptionPane.showMessageDialog(frame, str,
• Inane warning,
• JOptionPane.WARNING_MESSAGE)

38
Examples

• String str Eggs are not supposed to be
  green.
• JOptionPane.showMessageDialog(frame, str,
• Inane error,
• JOptionPane.ERROR_MESSAGE)
• JOptionPane.showMessageDialog(frame, str,
• A plain message,
• JOptionPane.A_PLAIN_MESSAGE)

39
Confirm Dialog

• int n JOptionPane.showConfirmDialog(frame,
• "Would you like green eggs and ham?",
• "An Inane Question",
• JOptionPane.YES_NO_OPTION)

40
Input Dialog

• Object possibilities "ham", "spam", "yam"
• String s (String)JOptionPane.showInputDialog(
• frame, "Complete the sentence\n
• \"Green eggs and...\"", "Customized Dialog",
• JOptionPane.PLAIN_MESSAGE, icon,
  possibilities,"ham")
• //If a string was returned, say so.
• if ((s ! null) (s.length() gt 0))
• setLabel("Green eggs and... " s "!")
• return
• //If you're here, the return value was
  null/empty.
• setLabel("Come on, finish the sentence!")
• int n JOptionPane.

41
Dialogs

• As the previous code snippets showed, the
  showMessageDialog, showConfirmDialog, and
  showOptionDialog methods return an integer
  indicating the user's choice.
• The values for this integer are YES_OPTION,
  NO_OPTION, CANCEL_OPTION, OK_OPTION, and
  CLOSED_OPTION. Each option corresponds to the
  button the user pressed.
• Exception when CLOSED_OPTION is returned, it
  indicates that the user closed the dialog window
  explicitly, rather than by choosing a button
  inside the option pane.
• http//java.sun.com/docs/books/tutorial/uiswing/
  
• components/dialog.html

42
JScrollPane

• A scroll pane is a component that supports
  automatically scrolling without coding.

http//www.cs.joensuu.fi/koles/edm/edm2.html
43
Menus

• Java provides several classesJMenuBar, JMenu,
  JMenuItem, JCheckBoxMenuItem, and
  JRadioButtonMenuItem to implement menus in a
  frame.
• A JFrame or JApplet can hold a menu bar to which
  the pull-down menus are attached.
• Menus consist of menu items that the user can
  select (or toggle on or off). Menu bars can be
  viewed as a structure to support menus.

44
Menu Demo
Menu Bar
Menu Items
45
The JMenuBar Class

• A menu bar holds menus the menu bar can only be
  added to a frame.
• Example Create and add a JMenuBar to a frame

• JFrame frame new JFrame()
• frame.setSize(300, 200)
• frame.setVisible(true)
• JMenuBar mb new JMenuBar()
  frame.setJMenuBar(mb)

46
The Menu Class

• Attach menus onto a JMenuBar.
• Example create two menus, File and Help, and
  add
• them to the JMenuBar mb

• JMenu fileMenu new JMenu("File", false)
• JMenu helpMenu new JMenu("Help", true)
• mb.add(fileMenu)
• mb.add(helpMenu)

47
The MenuItem Class

• Individual items of Menu.
• MenuItem()
• MenuItem(String ItemName)
• MenuItem(String ItemName,
• MenuShortcut keyAccel)

48
1. Create Menu Items

• JMenuItem jmiNew new JMenuItem("new")
• JMenuItem jmiOpen new JMenuItem("open")
• JMenuItem jmiPrint new JMenuItem("print")
• JMenuItem jmiExit new JMenuItem("exit")

49
2. Add Menu Items

• fileMenu.add(jmiNew)
• fileMenu.add(jmiOpen)
• fileMenu.add(new JMenuItem("-")) // separator
• fileMenu.add(jmiPrint)
• fileMenu.add(jmiExit)
• fileMenu.add(new JMenuItem("-")) // separator

50
3. Register Listener

• jmiNew.addActionListener(this)
• jmiOpen.addActionListener(this)
• jmiPrint.addActionListener(this)
• jmiExit.addActionListener(this)

51
4. Implement Handler

• public void actionPerformed(ActionEvent e)
• String actionCommand e.getActinCommand()
• if(e.getSource() isntanceof JMenuItem)
• if(New.equals(actionCommand))
• // DO IT!
• else if(Open.equals(actionCommand))
• // DO IT!
• else if(Print.equals(actionCommand))
• // DO IT!
• else if(Exit.equals(actionCommand))
• System.out(0)
• //e.getSource()
• //actionPerformed()