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

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

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

3 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 3 Chapter 12: Graphical User Interfaces 3 Use Panels to Organize Buttons JPanel buttonPanel = new JPanel(); buttonPanel.add(upButton); buttonPanel.add(downButton);... contentPane.add(buttonPanel, "South");

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

5 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 5 Chapter 12: Graphical User Interfaces 5 Layout Managers BorderLayout (center, south, north, east, west) FlowLayout (left-to-right) GridLayout (rectangular grid) Default: Content pane has border layout Default: Panels have flow layout Change default: panel.setLayout(new GridLayout(4, 3));

6 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 6 Chapter 12: Graphical User Interfaces 6 Figure 3 The Border Layout Grows Components

7 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 7 Chapter 12: Graphical User Interfaces 7 FlowLayout doesn't grow content The border layout and grid layout grow buttons etc. to fit the entire area of the border or grid Remedy: put button(s) inside panel with flow layout

8 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 8 Chapter 12: Graphical User Interfaces 8 Figure 4 Grid Layout

9 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 9 Chapter 12: Graphical User Interfaces 9 Grid Layout Add buttons left-to-right/top-to-bottom panel.add(button7); panel.add(button8); panel.add(button9); panel.add(button4);... panel.add(buttonCE);

10 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 10 Chapter 12: Graphical User Interfaces 10 Figure 5 Buttons with Labels and Icons

11 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 11 Chapter 12: Graphical User Interfaces 11 Buttons Specify label and optional icon in constructor JButton leftButton = new JButton("left"); leftButton = new JButton("left", new ImageIcon("left.gif")); Add action listener to handle “button click” event

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

13 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 13 Chapter 12: Graphical User Interfaces 13 } 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);

14 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 14 Chapter 12: Graphical User Interfaces 14 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);

15 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 15 Chapter 12: Graphical User Interfaces 15 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();

16 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 16 Chapter 12: Graphical User Interfaces 16 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); }

17 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 17 Chapter 12: Graphical User Interfaces 17 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); }

18 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 18 Chapter 12: Graphical User Interfaces 18 /** Moves the rectangle and repaints it. The rectangle is moved by multiples of its full width or height. @param dx the number of width units @param 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; }

19 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 19 Chapter 12: Graphical User Interfaces 19 Figure 6 A Frame with a Text Area and a Text Field

20 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 20 Chapter 12: Graphical User Interfaces 20 Text Components Specify number of rows/characters in constructor: tf = new TextField(5); ta = new TextArea(10, 40); Turn edit mode off if you want to display text ta.setEditable(false); Set text programmatically tf.setText("Hello");

21 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 21 Chapter 12: Graphical User Interfaces 21 Labels Use a label to tag a text field JLabel label = new JLabel("Name", SwingConstants.RIGHT); Add label to panel: panel.add(label); panel.add(nameField);

22 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 22 Chapter 12: Graphical User Interfaces 22 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();

23 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 23 Chapter 12: Graphical User Interfaces 23 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);

24 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 24 Chapter 12: Graphical User Interfaces 24 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

25 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 25 Chapter 12: Graphical User Interfaces 25 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 space. @param input the string containing the numbers @return 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;

26 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 26 Chapter 12: Graphical User Interfaces 26 } /** Computes the average of an array of floating-point numbers. @param data the numbers to average @return 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;

27 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 27 Chapter 12: Graphical User Interfaces 27 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); }

28 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 28 Chapter 12: Graphical User Interfaces 28 Figure 7 A Combo Box, Radio Buttons, and Check Boxes

29 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 29 Chapter 12: Graphical User Interfaces 29 Radio Buttons Radio buttons are mutually exclusive Button group turns one button off when the next one is turned on sButton = new JRadioButton("Small"); mButton = new JRadioButton("Medium"); lButton = new JRadioButton("Large"); buttonGroup.add(sbutton); buttonGroup.add(mbutton); buttonGroup.add(lbutton) Still need to add to panel

30 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 30 Chapter 12: Graphical User Interfaces 30 Check Boxes Similar to radio button, not mutually exclusive JCheckBox it = new JCheckBox("Italic"); Test if selected if (it.isSelected())...

31 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 31 Chapter 12: Graphical User Interfaces 31 Borders Use border to group related components Add border to panel holding components panel.setBorder(new TitledBorder(new EtchedBorder(), "Title"));

32 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 32 Chapter 12: Graphical User Interfaces 32 Figure 8 An Opened Combo Box

33 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 33 Chapter 12: Graphical User Interfaces 33 Combo boxes Use less space than radio buttons Users can type other values “Combo” between list selection and text field JComboBox faceName = new JComboBox(); faceName.addItem("Serif"); faceName.addItem("SansSerif");... Get user selection sel= (String)faceName.getSelectedItem();

34 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 34 Chapter 12: Graphical User Interfaces 34 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;

35 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 35 Chapter 12: Graphical User Interfaces 35 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

36 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 36 Chapter 12: Graphical User Interfaces 36 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);

37 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 37 Chapter 12: Graphical User Interfaces 37 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);

38 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 38 Chapter 12: Graphical User Interfaces 38 // 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

39 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 39 Chapter 12: Graphical User Interfaces 39 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. */

40 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 40 Chapter 12: Graphical User Interfaces 40 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;

41 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 41 Chapter 12: Graphical User Interfaces 41 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(); }

42 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 42 Chapter 12: Graphical User Interfaces 42 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); }

43 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 43 Chapter 12: Graphical User Interfaces 43 Figure 9 Pulldown Menus

44 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 44 Chapter 12: Graphical User Interfaces 44 Menus Add menu bar to frame JMenuBar bar = new JMenuBar(); frame.setJMenuBar(bar); Add menus to the menu bar JMenu fileMenu = new JMenu("File"); bar.add(fileMenu);

45 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 45 Chapter 12: Graphical User Interfaces 45 Menu items Add menu items to the menu JMenuItem fileNew = new JMenuItem("New"); Add action listener to the menu item ActionListener l =...; fileNew.addActionListener(l);

46 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 46 Chapter 12: Graphical User Interfaces 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;

47 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 47 Chapter 12: Graphical User Interfaces 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

48 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 48 Chapter 12: Graphical User Interfaces 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);

49 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 49 Chapter 12: Graphical User Interfaces 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);

50 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 50 Chapter 12: Graphical User Interfaces 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;

51 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 51 Chapter 12: Graphical User Interfaces 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);

52 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 52 Chapter 12: Graphical User Interfaces 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); }

53 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 53 Chapter 12: Graphical User Interfaces 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(); }

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

55 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 55 Chapter 12: Graphical User Interfaces 55 /** Moves the rectangle and repaints it. The rectangle is moved by multiples of its full width or height. @param dx the number of width units @param 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; }

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

57 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 57 Chapter 12: Graphical User Interfaces 57 Figure 11 A Demonstration Application from the Java Development Kit

58 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 58 Chapter 12: Graphical User Interfaces 58 Exploring the Documentation Don't try to understand all methods Focus on what you need to do your job –How do I construct a slider? –How can I get notified when the user has moved it? –How can I tell what the user has set it to? When you complete the basics, look again –How about those “tick marks”?

59 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 59 Chapter 12: Graphical User Interfaces 59 Figure 12 A Mysterious Entry in the JSlider Documentation

60 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 60 Chapter 12: Graphical User Interfaces 60 How to construct a slider JSlider() Has range (0,100) JSlider(int min, int max, int value) Can specify range and initial value JSlider(BoundedRangeModel m) appears to be some internal mechanism

61 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 61 Chapter 12: Graphical User Interfaces 61 How to get notifications Look for “addXxxListener”: void addChangeListener(ChangeListener l) What is a change listener? It has a single method void stateChanged(ChangeEvent e) Plan: Add a change listener, read slider state and update color in that method

62 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 62 Chapter 12: Graphical User Interfaces 62 How to get slider setting Look at all methods that start with “get”: int getValue() R eturns the slider's value

63 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 63 Chapter 12: Graphical User Interfaces 63 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;

64 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 64 Chapter 12: Graphical User Interfaces 64 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();

65 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 65 Chapter 12: Graphical User Interfaces 65 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));

66 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 66 Chapter 12: Graphical User Interfaces 66 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. */

67 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 67 Chapter 12: Graphical User Interfaces 67 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;

68 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 68 Chapter 12: Graphical User Interfaces 68 private class ColorListener implements ChangeListener { public void stateChanged(ChangeEvent event) { setSampleColor(); } private class WindowCloser extends WindowAdapter { public void windowClosing(WindowEvent event) { System.exit(0); }

69 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e 69 Chapter 12: Graphical User Interfaces 69 Figure 13 Visual Programming Environment

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