Chapter 12: Graphical User Interfaces 1 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 1 Chapter 12 Graphical User Interfaces JAVA

Chapter 12: Graphical User Interfaces 2 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 2 Structure Predefined structure –Jbutton –Jpanel –Jframe –contentPane –Container

Chapter 12: Graphical User Interfaces 3 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 3 Figure 1 A Program with Four Buttons contentPane with border layout Panel with flow layout

Chapter 12: Graphical User Interfaces 4 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 4 Layout Management JAVA Swing Add buttons – contentPane.add(upButton, “South”); – contentPane.add(downbutton, “South”); //error Jpanel buttonPanel = new Jpanel(); buttonPanel.add(upButton); buttonPanel.add(downButton); buttonPanel.add(leftButton); buttonPanel.add(rigtButton); contentPane.add(buttonPanel, “South”);

Chapter 12: Graphical User Interfaces 5 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 5 Layout Management Border layout Flow layout Grid layout Build up user interfaces by adding components into containers. The content pane is a container (Jpanel) Content pane (default: border layout) Panel (default: flow layout)

Chapter 12: Graphical User Interfaces 6 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 6 Layout Management Border layout: grows each component to fill all available space in its area. The flow layout leaves each component at its preferred size. The grid layout arranges components in a grid with a fixed number of rows and columns, resizing each of the component.

Chapter 12: Graphical User Interfaces 7 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 7 Border Layout Panel Jpanel panel = new Jpanel(); panel.setLayout(new BorderLayout());

Chapter 12: Graphical User Interfaces 8 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 8 Figure 2 Containers with Separate Layout Managers

Chapter 12: Graphical User Interfaces 9 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 9 Figure 3 The Border Layout Grows Components

Chapter 12: Graphical User Interfaces 10 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 10 Grid Layout Jpanel numberPanel = new Jpanel(); numberPanel.setLayout(new GridLayout(4,3)); numberPanel.add(button7); numberPanel.add(button8); numberPanel.add(button9); numberPanel.add(button4); …

Chapter 12: Graphical User Interfaces 11 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 11 Figure 4 Grid Layout

Chapter 12: Graphical User Interfaces 12 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 12 Buttons When a button is clicked, it sends an action event. You need an action listener. leftButton = new JButton(“Left”); leftButton = new JButton(new ImageIcon(“left.gif”)); leftButton = new(“Left, new ImageIcon(“left.gif”));

Chapter 12: Graphical User Interfaces 13 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 13 Figure 5 Buttons with Labels and Icons

Chapter 12: Graphical User Interfaces 14 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 14 Listener Individual listener upButton =new Jbutton(“UP”); ActionListener listener = new UpListener(); upButton.addActionListener(listener); Jbutton upButton; private class UpListener implements … Unified listener – actionPerformed method –getSource method of the ActionEvent parameter

Chapter 12: Graphical User Interfaces 15 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 15 Program ButtonTest.java import java.awt.Container; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Rectangle; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JPanel; public class ButtonTest { public static void main(String[] args) { ButtonFrame frame = new ButtonFrame(); frame.setTitle("ButtonTest"); frame.show();

Chapter 12: Graphical User Interfaces 16 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 16 } class ButtonFrame extends JFrame { public ButtonFrame() { final int DEFAULT_FRAME_WIDTH = 300; final int DEFAULT_FRAME_HEIGHT = 300; setSize(DEFAULT_FRAME_WIDTH,DEFAULT_FRAME_HEIGHT); addWindowListener(new WindowCloser()); // construct components panel = new RectanglePanel(); JPanel buttonPanel = new JPanel(); ActionListener listener = new DirectionListener(); upButton = new JButton("Up"); upButton.addActionListener(listener);

Chapter 12: Graphical User Interfaces 17 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 17 downButton = new JButton("Down"); downButton.addActionListener(listener); leftButton = new JButton("Left"); leftButton.addActionListener(listener); rightButton = new JButton("Right"); rightButton.addActionListener(listener); // add components to content pane Container contentPane = getContentPane(); contentPane.add(panel, "Center"); buttonPanel.add(upButton); buttonPanel.add(downButton); buttonPanel.add(leftButton); buttonPanel.add(rightButton);

Chapter 12: Graphical User Interfaces 18 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 18 contentPane.add(buttonPanel, "South"); } private RectanglePanel panel; private JButton upButton; private JButton downButton; private JButton leftButton; private JButton rightButton; // inner class definition private class DirectionListener implements ActionListener { public void actionPerformed(ActionEvent event) { // find the button that was clicked Object source = event.getSource();

Chapter 12: Graphical User Interfaces 19 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 19 if (source == upButton) panel.moveRectangle(0, -1); else if (source == downButton) panel.moveRectangle(0, 1); else if (source == leftButton) panel.moveRectangle(-1, 0); else if (source == rightButton) panel.moveRectangle(1, 0); } private class WindowCloser extends WindowAdapter { public void windowClosing(WindowEvent event) { System.exit(0); }

Chapter 12: Graphical User Interfaces 20 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 20 class RectanglePanel extends JPanel { public RectanglePanel() { rect = new Rectangle(0, 0, RECT_WIDTH, RECT_HEIGHT); } public void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2 = (Graphics2D)g; g2.draw(rect); }

Chapter 12: Graphical User Interfaces 21 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 21 /** Moves the rectangle and repaints it. The rectangle is moved by multiples of its full width or dx the number of width dy the number of height units */ public void moveRectangle(int dx, int dy) { rect.translate(dx * RECT_WIDTH, dy * RECT_HEIGHT); repaint(); } private Rectangle rect; private static final int RECT_WIDTH = 20; private static final int RECT_HEIGHT = 30; }

Chapter 12: Graphical User Interfaces 22 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 22 Common Errors of the Button Do not identify components by their label text. Forgetting to attach a listener.

Chapter 12: Graphical User Interfaces 23 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 23 Text Components JTextArea class Both JTextField and JTextArea are subclasses of the JTextComponent class. Number of characters – JTextFiled interestRateField = new JTextField(5); Rows and columns –JTextArea resultArea = new JTextArea(10, 40)

Chapter 12: Graphical User Interfaces 24 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 24 Text Components setEditalbe –JTextField result = new JTextField(); – result.setEditable(false); setFont method

Chapter 12: Graphical User Interfaces 25 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 25 Figure 6 A Frame with a Text Area and a Text Field

Chapter 12: Graphical User Interfaces 26 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 26 Program TextTest.java import java.awt.Container; import java.awt.GridLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.util.StringTokenizer; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JTextArea; import javax.swing.JTextField; public class TextTest { public static void main(String[] args) { TextFrame frame = new TextFrame();

Chapter 12: Graphical User Interfaces 27 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 27 frame.setTitle("TextTest"); frame.show(); } class TextFrame extends JFrame { public TextFrame() { final int DEFAULT_FRAME_WIDTH = 300; final int DEFAULT_FRAME_HEIGHT = 300; setSize(DEFAULT_FRAME_WIDTH, DEFAULT_FRAME_HEIGHT); addWindowListener(new WindowCloser()); // construct components inputArea = new JTextArea(); resultField = new JTextField(20); resultField.setEditable(false);

Chapter 12: Graphical User Interfaces 28 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 28 calcButton = new JButton("Calculate"); calcButton.addActionListener(new ButtonListener()); // add components to content pane Container contentPane = getContentPane(); contentPane.add(inputArea, "Center"); // arrange the label and text field in a panel JPanel resultPanel = new JPanel(); resultPanel.add(new JLabel("Average:")); resultPanel.add(resultField); // place the button in a panel JPanel buttonPanel = new JPanel(); buttonPanel.add(calcButton); // stack up these two panels in another panel

Chapter 12: Graphical User Interfaces 29 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 29 JPanel southPanel = new JPanel(); southPanel.setLayout(new GridLayout(2, 1)); southPanel.add(resultPanel); southPanel.add(buttonPanel); contentPane.add(southPanel, "South"); } /** Reads numbers from a string that contains a sequence of floating-point numbers separated by white input the string containing the the numbers that were found in the string */ public static double[] getData(String input) { StringTokenizer tokenizer = new StringTokenizer(input); double[] data = new double[tokenizer.countTokens()]; for (int i = 0; i < data.length; i++) data[i] = Double.parseDouble(tokenizer.nextToken()); return data;

Chapter 12: Graphical User Interfaces 30 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 30 } /** Computes the average of an array of floating-point data the numbers to the average, or 0 if the array was empty */ public static double average(double[] data) { if (data.length == 0) return 0; double sum = 0; for (int i = 0; i < data.length; i++) sum = sum + data[i]; return sum / data.length; } private JTextArea inputArea; private JTextField resultField; private JButton calcButton;

Chapter 12: Graphical User Interfaces 31 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 31 private class ButtonListener implements ActionListener { public void actionPerformed(ActionEvent event) { // get user input from text area double[] data = getData(inputArea.getText()); // compute average and display in result field double avg = average(data); resultField.setText("” + avg); } private class WindowCloser extends WindowAdapter { public void windowClosing(WindowEvent event) { System.exit(0); }

Chapter 12: Graphical User Interfaces 32 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 32 Choices Radio Buttons (mutually exclusive) Check boxes (not mutually exclusive) Combo Boxes

Chapter 12: Graphical User Interfaces 33 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 33 Figure 7 A Combo Box, Radio Buttons, and Check Boxes

Chapter 12: Graphical User Interfaces 34 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 34 Figure 8 An Opened Combo Box

Chapter 12: Graphical User Interfaces 35 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 35 Program ChoiceTest.java import java.awt.Container; import java.awt.Font; import java.awt.GridLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import javax.swing.ButtonGroup; import javax.swing.JButton; import javax.swing.JCheckBox; import javax.swing.JComboBox; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JRadioButton; import javax.swing.JTextField; import javax.swing.border.EtchedBorder; import javax.swing.border.TitledBorder;

Chapter 12: Graphical User Interfaces 36 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 36 public class ChoiceTest { public static void main(String[] args) { ChoiceFrame frame = new ChoiceFrame(); frame.setTitle("ChoiceTest"); frame.show(); } class ChoiceFrame extends JFrame { public ChoiceFrame() { final int DEFAULT_FRAME_WIDTH = 300; final int DEFAULT_FRAME_HEIGHT = 300; setSize(DEFAULT_FRAME_WIDTH, DEFAULT_FRAME_HEIGHT); addWindowListener(new WindowCloser()); // construct components

Chapter 12: Graphical User Interfaces 37 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 37 sampleField = new JTextField ("Computing Concepts with Java Essentials"); sampleField.setEditable(false); ChoiceListener listener = new ChoiceListener(); facenameCombo = new JComboBox(); facenameCombo.addItem("Serif"); facenameCombo.addItem("SansSerif"); facenameCombo.addItem("Monospaced"); facenameCombo.setEditable(true); facenameCombo.addActionListener(listener); italicCheckBox = new JCheckBox("Italic"); italicCheckBox.addActionListener(listener); boldCheckBox = new JCheckBox("Bold"); boldCheckBox.addActionListener(listener);

Chapter 12: Graphical User Interfaces 38 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 38 smallButton = new JRadioButton("Small"); smallButton.setSelected(true); smallButton.addActionListener(listener); mediumButton = new JRadioButton("Medium"); mediumButton.addActionListener(listener); largeButton = new JRadioButton("Large"); largeButton.addActionListener(listener); // add radio buttons to button group ButtonGroup sizeGroup = new ButtonGroup(); sizeGroup.add(smallButton); sizeGroup.add(mediumButton); sizeGroup.add(largeButton);

Chapter 12: Graphical User Interfaces 39 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 39 // add components to panels JPanel facenamePanel = new JPanel(); facenamePanel.add(facenameCombo); JPanel sizeGroupPanel = new JPanel(); sizeGroupPanel.add(smallButton); sizeGroupPanel.add(mediumButton); sizeGroupPanel.add(largeButton); sizeGroupPanel.setBorder (new TitledBorder(new EtchedBorder(), "Size")); JPanel styleGroupPanel = new JPanel(); styleGroupPanel.add(italicCheckBox); styleGroupPanel.add(boldCheckBox); styleGroupPanel.setBorder (new TitledBorder(new EtchedBorder(), "Style")); // line up component panels

Chapter 12: Graphical User Interfaces 40 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 40 JPanel southPanel = new JPanel(); southPanel.setLayout(new GridLayout(3, 1)); southPanel.add(facenamePanel); southPanel.add(sizeGroupPanel); southPanel.add(styleGroupPanel); // add panels to content pane Container contentPane = getContentPane(); contentPane.add(sampleField, "Center"); contentPane.add(southPanel, "South"); setSampleFont(); } /** Gets user choice for font name, style, and size and sets the font of the text field. */

Chapter 12: Graphical User Interfaces 41 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 41 public void setSampleFont() { // get font name String facename = (String)facenameCombo.getSelectedItem(); // get font style int style = 0; if (italicCheckBox.isSelected()) style = style + Font.ITALIC; if (boldCheckBox.isSelected()) style = style + Font.BOLD; // get font size final int SMALL_SIZE = 12; final int MEDIUM_SIZE = 16; final int LARGE_SIZE = 24;

Chapter 12: Graphical User Interfaces 42 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 42 int size = 0; if (smallButton.isSelected()) size = SMALL_SIZE; else if (mediumButton.isSelected()) size = MEDIUM_SIZE; else if (largeButton.isSelected()) size = LARGE_SIZE; // set font of text field sampleField.setFont(new Font(facename, style, size)); sampleField.repaint(); }

Chapter 12: Graphical User Interfaces 43 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 43 private JTextField sampleField; private JCheckBox italicCheckBox; private JCheckBox boldCheckBox; private JRadioButton smallButton; private JRadioButton mediumButton; private JRadioButton largeButton; private JComboBox facenameCombo; private class ChoiceListener implements ActionListener { public void actionPerformed(ActionEvent event) { setSampleFont(); } private class WindowCloser extends WindowAdapter { public void windowClosing(WindowEvent event) { System.exit(0); }

Chapter 12: Graphical User Interfaces 44 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 44 Menus Add a listener to each menu item.

Chapter 12: Graphical User Interfaces 45 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 45 Figure 9 Pulldown Menus

Chapter 12: Graphical User Interfaces 46 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 46 Program MenuTest.java import java.awt.Container; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Rectangle; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.util.Random; import javax.swing.JFrame; import javax.swing.JMenu; import javax.swing.JMenuBar; import javax.swing.JMenuItem; import javax.swing.JPanel;

Chapter 12: Graphical User Interfaces 47 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 47 public class MenuTest { public static void main(String[] args) { MenuFrame frame = new MenuFrame(); frame.setTitle("MenuTest"); frame.show(); } class MenuFrame extends JFrame { public MenuFrame() { final int DEFAULT_FRAME_WIDTH = 300; final int DEFAULT_FRAME_HEIGHT = 300; setSize(DEFAULT_FRAME_WIDTH, DEFAULT_FRAME_HEIGHT); addWindowListener(new WindowCloser()); // add drawing panel to content pane

Chapter 12: Graphical User Interfaces 48 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 48 panel = new RectanglePanel(); Container contentPane = getContentPane(); contentPane.add(panel, "Center"); // construct menu JMenuBar menuBar = new JMenuBar(); setJMenuBar(menuBar); JMenu fileMenu = new JMenu("File"); menuBar.add(fileMenu); MenuListener listener = new MenuListener(); newMenuItem = new JMenuItem("New"); fileMenu.add(newMenuItem); newMenuItem.addActionListener(listener);

Chapter 12: Graphical User Interfaces 49 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 49 exitMenuItem = new JMenuItem("Exit"); fileMenu.add(exitMenuItem); exitMenuItem.addActionListener(listener); JMenu editMenu = new JMenu("Edit"); menuBar.add(editMenu); JMenuItem moveMenu = new JMenu("Move"); editMenu.add(moveMenu); upMenuItem = new JMenuItem("Up"); moveMenu.add(upMenuItem); upMenuItem.addActionListener(listener); downMenuItem = new JMenuItem("Down"); moveMenu.add(downMenuItem); downMenuItem.addActionListener(listener);

Chapter 12: Graphical User Interfaces 50 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 50 leftMenuItem = new JMenuItem("Left"); moveMenu.add(leftMenuItem); leftMenuItem.addActionListener(listener); rightMenuItem = new JMenuItem("Right"); moveMenu.add(rightMenuItem); rightMenuItem.addActionListener(listener); randomizeMenuItem = new JMenuItem("Randomize"); editMenu.add(randomizeMenuItem); randomizeMenuItem.addActionListener(listener); } private JMenuItem exitMenuItem; private JMenuItem newMenuItem; private JMenuItem upMenuItem; private JMenuItem downMenuItem; private JMenuItem leftMenuItem; private JMenuItem rightMenuItem;

Chapter 12: Graphical User Interfaces 51 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 51 private JMenuItem randomizeMenuItem; private RectanglePanel panel; private class MenuListener implements ActionListener { public void actionPerformed(ActionEvent event) { // find the menu that was selected Object source = event.getSource(); if (source == exitMenuItem) System.exit(0); else if (source == newMenuItem) panel.reset(); else if (source == upMenuItem) panel.moveRectangle(0, -1); else if (source == downMenuItem) panel.moveRectangle(0, 1); else if (source == leftMenuItem) panel.moveRectangle(-1, 0);

Chapter 12: Graphical User Interfaces 52 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 52 else if (source == rightMenuItem) panel.moveRectangle(1, 0); else if (source == randomizeMenuItem) panel.randomize(); } private class WindowCloser extends WindowAdapter { public void windowClosing(WindowEvent event) { System.exit(0); } class RectanglePanel extends JPanel { public RectanglePanel() { rect = new Rectangle(0, 0, RECT_WIDTH, RECT_HEIGHT); }

Chapter 12: Graphical User Interfaces 53 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 53 public void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2 = (Graphics2D)g; g2.draw(rect); } /** Resets the rectangle to the top left corner. */ public void reset() { rect.setLocation(0, 0); repaint(); }

Chapter 12: Graphical User Interfaces 54 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 54 /** Moves the rectangle to a random position. */ public void randomize() { Random generator = new Random(); rect.setLocation(generator.nextInt(getWidth()), generator.nextInt(getHeight())); repaint(); }

Chapter 12: Graphical User Interfaces 55 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 55 /** Moves the rectangle and repaints it. The rectangle is moved by multiples of its full width or dx the number of width dy the number of height units */ public void moveRectangle(int dx, int dy) { rect.translate(dx * RECT_WIDTH, dy * RECT_HEIGHT); repaint(); } private Rectangle rect; private static int RECT_WIDTH = 20; private static int RECT_HEIGHT = 30; }

Chapter 12: Graphical User Interfaces 56 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 56 Figure 10 A Color Mixer

Chapter 12: Graphical User Interfaces 57 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 57 Program SliderTest.java import java.awt.Color; import java.awt.Container; import java.awt.GridLayout; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JSlider; import javax.swing.SwingConstants; import javax.swing.event.ChangeListener; import javax.swing.event.ChangeEvent;

Chapter 12: Graphical User Interfaces 58 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 58 public class SliderTest { public static void main(String[] args) { SliderFrame frame = new SliderFrame(); frame.setTitle("SliderTest"); frame.show(); } class SliderFrame extends JFrame { public SliderFrame() { final int DEFAULT_FRAME_WIDTH = 300; final int DEFAULT_FRAME_HEIGHT = 300; setSize(DEFAULT_FRAME_WIDTH, DEFAULT_FRAME_HEIGHT); addWindowListener(new WindowCloser()); // construct components colorPanel = new JPanel();

Chapter 12: Graphical User Interfaces 59 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 59 ColorListener listener = new ColorListener(); redSlider = new JSlider(0, 100, 100); redSlider.addChangeListener(listener); greenSlider = new JSlider(0, 100, 70); greenSlider.addChangeListener(listener); blueSlider = new JSlider(0, 100, 70); blueSlider.addChangeListener(listener); // fill content pane JPanel southPanel = new JPanel(); southPanel.setLayout(new GridLayout(3, 2)); southPanel.add(new JLabel("Red", SwingConstants.RIGHT));

Chapter 12: Graphical User Interfaces 60 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 60 southPanel.add(redSlider); southPanel.add(new JLabel("Green", SwingConstants.RIGHT)); southPanel.add(greenSlider); southPanel.add(new JLabel("Blue", SwingConstants.RIGHT)); southPanel.add(blueSlider); Container contentPane = getContentPane(); contentPane.add(colorPanel, "Center"); contentPane.add(southPanel, "South"); setSampleColor(); } /** Reads the slider values and sets the panel to the selected color. */

Chapter 12: Graphical User Interfaces 61 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 61 public void setSampleColor() { // read slider values float red = 0.01F * redSlider.getValue(); float green = 0.01F * greenSlider.getValue(); float blue = 0.01F * blueSlider.getValue(); // set panel background to selected color colorPanel.setBackground(new Color(red, green, blue)); colorPanel.repaint(); } private JPanel colorPanel; private JSlider redSlider; private JSlider greenSlider; private JSlider blueSlider;

Chapter 12: Graphical User Interfaces 62 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 62 private class ColorListener implements ChangeListener { public void stateChanged(ChangeEvent event) { setSampleColor(); } private class WindowCloser extends WindowAdapter { public void windowClosing(WindowEvent event) { System.exit(0); }

Chapter 12: Graphical User Interfaces 63 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 63 Homework P12.3 Calculator with + - * / operations Use grid layout and text.