Combo Box, Check Boxes, and Radio Buttons

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Combo Box, Check Boxes, and Radio Buttons
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Radio Buttons

• User can click radio buttons, just like other
  buttons
• BUT Radio buttons are mutually
  exclusive
• This is achieved by placing all associated
  buttons in a ButtonGroup object. The ButtonGroup
  turns 1 button off when the next one is turned on
• sButton new JRadioButton("Small")mButton
  new JRadioButton("Medium") lButton new
  JRadioButton("Large")ButtonGroup group new
  ButtonGroup()group.add(sbutton)group.add(mbutt
  on)group.add(lbutton)

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Radio Buttons continued

• It is good practice to initialize one of the
  buttons to ON
• sButton.setSelected(true)
• The ButtonGroup is not a visual component.
• (You dont place it into a panel)
• The buttons still need to be placed into a
  panel individually.
• panel.add(sButton)
• panel.add(mButton)
• panel.add(lButton)

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Radio Buttons continued

• Your code can tell if a RadioButton is selected
• if (sButton.isSelected())
• . . .
• One usually wants to check which button is
  selected WHEN THE USER HAS clicked on ONE!!
• An ActionEvent is created when the user clicks
  on one of the buttons .. so this code is in an
  ActionListener !!

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• // Frame which allows the use to select its
  background color
• import javax.swing.
• import java.awt.event.
• import java.awt.Color
• import java.awt.BorderLayout
• public class RadDemo extends JFrame
• public RadDemo()
• createpanel() //set
  up panel
• pack()

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• public void createpanel()
• 
  //set up button and put in panel
• final JRadioButton redbtn new
  JRadioButton("RED")
• final JRadioButton bluebtn new
  JRadioButton("BLUE")
• final JRadioButton greenbtn new
  JRadioButton("GREEN")
• ButtonGroup grp new ButtonGroup()
• grp.add(redbtn)
• grp.add(bluebtn)
• grp.add(greenbtn)
• final JPanel btnpanel new JPanel()
  //put on panel
• btnpanel.add(redbtn)
• btnpanel.add(bluebtn)
• btnpanel.add(greenbtn)

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• redbtn.setSelected(true)
  //default button/color is red
• btnpanel.setBackground(Color.RED)
• class BtnListen implements ActionListener
  //define listener class
• public void actionPerformed (ActionEvent
  e)
• if (redbtn.isSelected() )
• btnpanel.setBackground(Color.RED)
  
• else if (bluebtn.isSelected() )
• btnpanel.setBackground(Color.BLUE
  )
• else
• btnpanel.setBackground(Color.GREE
  N)
• BtnListen blisten new BtnListen()
  //create and register listener object
• redbtn.addActionListener(blisten)
• bluebtn.addActionListener(blisten)
• greenbtn.addActionListener(blisten)
• getContentPane().add(btnpanel,
  BorderLayout.CENTER) //put on frame

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• // main to create and show frame
• public class ColorPanel
• public static void main (String args)
• //create and test one of these frames
• JFrame newframe new RadDemo()
• newframe.show()

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Check Boxes

• Similar to radio button, not mutually exclusive
• JCheckBox it new JCheckBox("Italic")
• JCheckBox bld new JCheckBox(Bold)
• Don't place into button group
• in Action listener ..
• If (it.isSelected() )
• . . .

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Combo Boxes

• Combination of selection and text field
• Create JComboBox object, then add the items
• JComboBox faceName new JComboBox()faceName.add
  Item("Serif")faceName.addItem("SansSerif"). .
  .
• (Any object type can be added to ComboBox
  --toString determines display)

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Combo Boxes

• To initialize the ComboBox selection
• facename.setSelectedItem(Italics)
• To get user selectionsel (String)faceName.getSe
  lectedItem()
• Cast needed because return type is Object !!
• An ActionEvent is created by a ComboBox if the
  user makes a choice!!

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Combo Boxes stored indexed items

• Another way to initialize the ComboBox selection
• facename.setSelectedIndex(0)
• Accordingly, can get user selectionint ind
  faceName.getSelectedIndex()

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• //method returns a panel with a combo box on it
• public JPanel makebottom()
• final JTextField outbox new JTextField("
  15.00", 10)
• //set up combo
  box and add a listener
• final JComboBox cbox new JComboBox()
• cbox.addItem("Large Price")
• cbox.addItem("Medium Price")
• cbox.addItem("Small Price")
• cbox.setSelectedItem("Large Price")

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• //method continues
• 
  //set up listener
• class BoxListener implements ActionListener
• public void actionPerformed(ActionEv
  ent e)
• if (cbox.getSelectedItem().equals("La
  rge Price"))
• outbox.setText("15.00")
• else if (cbox.getSelectedItem().equals
  ("Medium Price"))
• outbox.setText("10.00")
• else
• outbox.setText("8.00")
• BoxListener clisten new BoxListener()
• cbox.addActionListener(clisten)
• JPanel temp new JPanel()
  //set up panel
• temp.setBackground(Color.blue)
• temp.add(cbox)
• temp.add(outbox)
• return temp

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• JPanel temp new JPanel()
  //set up panel
• temp.setBackground(Color.blue)
• temp.add(cbox)
• temp.add(outbox)
• return temp
• //This method is used in file PizzaFrame.java