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CS 209 Programming in Java
#13 Multimedia
Part of Textbook Chapter 14
Spring, 2006
Instructor: J.G. Neal
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Topics
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Multimedia
Displaying Images
Using the MediaTracker class
Images in Applets and Applications
Playing Audio Clips
Audio Clips in Applets
Using the Timer Class for Animation
Example Programs
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Multimedia
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Media
– Can include images, audio, video, etc.
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Java program needs to:
– Get the media files
– Display/play/pause/replay/stop the media objects
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How to handle media in:
– Applets
– Applications
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Image Display – Relevant Classes
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Relevant classes for getting and displaying Images:
1. Use the Toolkit class and its methods such as
getDefaultToolkit and getImage
2. Use the Applet class and its methods such as
getCodeBase, getImage
3. Use the Class class and its methods such as getResouce
4. Use the Image class and its methods such as getHeight
and getWidth
5. Use the Graphics class and its method drawImage
6. Use the ImageIcon class and its methods such as
loadImage and paintIcon
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Methods Used to Get an Image for Display
Methods in the Applet class
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Get base URL
– URL getCodeBase() - Gets the base URL for folder
– URL getDocumentBase() - Returns an absolute URL for the
document in which the applet is embedded
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Get the image
– public Image getImage(URL url)
– public Image getImage(URL url, String filename)
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Getting Images in a Java Program
Approach 1:
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Use JApplet methods getCodeBase and getImage
Example:
String imagePath0 = "images/dukeWave.gif";
String imagePath1 = "images/duke2.gif";
img0 = getImage(getCodeBase(), imagePath0);
img1 = getImage(getCodeBase(), imagePath1);
try {
mt.addImage(img0, 0);
mt.addImage(img1, 0);
mt.waitForID(0);
} catch (Exception ex) {
System.out.println("\n" + ex.toString());
}
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Getting Images in a Java Program
Approach 2:
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Use the URL class and method getResource from class Class
Example:
String imagePath0a = "../images/dukeWave.gif";
String imagePath1a = "../images/duke2.gif";
Class object = this.getClass();
URL url0 = object.getResource(imagePath0a);
URL url1 = object.getResource(imagePath1a);
System.out.println("url0 = " + url0.toString());
System.out.println("url1 = " + url1.toString());
if ((url0 != null) && (url1 != null)) {
img0 = getImage(url0);
img1 = getImage(url1);
try {
mt.addImage(img0, 0);
mt.addImage(img1, 0);
mt.waitForID(0);
} catch (Exception ex) {
System.out.println("\n" + ex.toString());
}
}
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Getting Images in a Java Program
Approach 3:
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Use the Toolkit class
– Static Toolkit getDefaultToolkit() - Gets the default AWT
toolkit
– Image getImage(String filename) - Returns an image which gets
pixel data from the specified file, whose format can be either GIF,
JPEG or PNG
– Image getImage(URL url) - Returns an image which gets pixel data
from the specified URL
– Also has methods to:
• Get the screen resolution in dots-per-inch
• Get the screen size
• Get the system clipboard
• Among others
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Example:
img[i] = Toolkit.getDefaultToolkit().getImage(imgFileName);
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Displaying Images Using Graphics Methods
Methods in the Graphics class to draw the image
• drawImage(Image img, int x, int y, Color bgcolor,
ImageObserver observer) - Draws the image in the specified
location. The image’s upper left corner is at (x, y) in the coordinate
space of the graphics context. Transparent pixels are drawn in the
bgcolor. The observer is the object on which the image is
displayed. The image is cut off if it is larger than the area upon
which it is drawn.
• drawImage(Image img, int x, int y, ImageObserver
observer) - Same as above, but no bgcolor.
• drawImage(Image img, int x, int y, int width, int
height, ImageObserver observer) - Draws a scaled
version of the image.
• drawImage(Image img, int x, int y, int width, int
height, ImageObserver observer) - Same as above, but
includes background color.
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MediaTracker Class
• A utility class to track the status of media objects
– In the package: java.awt
– Use the import statement: import java.awt.MediaTracker;
– Or use import statement: import java.awt.*;
• Media objects
– Could include images, audio clips, etc.
– As of j2sdk1.4.0, only images were supported
(continued on next slide)
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MediaTracker Class (cont.)
To use a MediaTracker:
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Create an instance of the MediaTracker class
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Call the MediaTracker addImage method for each image to be
tracked
– MediaTracker(Component c) - Track for component c
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– addImage(Image image, int id) - adds an image to the list
of images being tracked by this media tracker
– addImage(Image image, int id, int w, int h) - adds
a scaled image to the list of images being tracked by this tracker
Call the MediaTracker checkAll method
– checkAll() - checks to see if all images being tracked by this
media tracker have finished loading; does not start loading any
images
– checkAll(boolean load) - checks to see if all images being
tracked by this media tracker have finished loading; if the
parameter is true, this method starts loading any images that are
not yet being loaded
(continued on next slide)
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MediaTracker Class (cont.)
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Each image can be assigned a priority level identifier ID
– The ID controls the priority order in which images are
fetched
– The ID is commonly not unique per image
– Images with a lower ID are loaded in preference to those
with a higher ID number
Call one of the “wait” methods to control processing
– void waitForAll() - starts loading all tracked images;
waits until all the images being tracked have finished loading
– void waitForID(int id) - starts loading all tracked
images with specified ID (priority level); waits until all the
images with the specified ID have finished loading
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Example Java Program
• Purpose: To demonstrate
– Use of images in a Java program
– Providing adequate display area and scroll capabilities
• Program:
– Class name: ImageEx
– Package name: mymediaexs
– Project name: MyMediaExs
• Program code:
– See next pages
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Example Program Execution
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Printing C:\Documents and Settings\jgneal\My Documents\MyDev\MyJava\MyMedia\MyMediaExs\src\mymediaexs\ImageEx.java at 4/27/06 5:16
1 package
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4 import
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6 import
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8 public class ImageEx extends JFrame {
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// Instance variables
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private
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private
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private
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private Image img = null
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private MediaTracker mt = new MediaTracker( this
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private int
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private float
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private float
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// The main method required for an application program
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public static void main( String[] args ) {
// Construct the window
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JFrame frame = new ImageEx
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frame.setSize(new Dimension
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frame.setDefaultCloseOperation
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frame.setVisible( true
// Make the window visible
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}
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public ImageEx() {
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super
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Container c = getContentPane
// Get content pane for JFrame
window
// Set layout manager for
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c.setLayout( new BorderLayout
window
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CanvasPanel cPan = new CanvasPanel
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img = Toolkit.getDefaultToolkit().getImage
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try {
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mt.addImage
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mt.waitForID
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System.out.println
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} catch ( Exception ex ) {
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System.out.println( "\n" + ex.toString
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}
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h = img.getHeight( null
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w = img.getWidth( null
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cPan.setPreferredSize( new Dimension( Math.round(scaleFactorUp *
w),
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Math.round((scaleFactorUp +
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Printing C:\Documents and Settings\jgneal\My Documents\MyDev\MyJava\MyMedia\MyMediaExs\src\mymediaexs\ImageEx.java at 4/27/06 5:16
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cPan.setVisible( true
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JScrollPane jscrollpane = new JScrollPane(cPan,
ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS,
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c.add
}
// Class to provide a drawing surface for graphics display
class CanvasPanel extends JPanel {
// Constructor
public CanvasPanel() {
setBackground
}
public void paintComponent ( Graphics g ) {
super.paintComponent
int
int
int
g.drawString( "Image Width: " + w + ", Height: " + h, xPos, yPos
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g.drawImage( img, xPos, yPos + sp, null
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// Draw scaled down version of image using method drawImage
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int wDown = Math.round
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int hDown = Math.round
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g.drawString( "Image scaled down by factor of: " +
scaleFactorDown +
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",
Width: " + wDown + ",
Height: " + hDown,
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g.drawImage( img, xPos, 5*sp + h, wDown, hDown, null
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// Create new scaled up version of image and draw it
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int wUp = Math.round
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int hUp = Math.round
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g.drawString( "Image scaled up by factor of: " + scaleFactorUp +
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",
Width: " + w*scaleFactorUp + ",
Height: "
+ h*scaleFactorUp,
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g.drawImage( img, xPos, 8*sp + h + hDown, wUp, hUp, null
}
} // End canvasPanel class
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Displaying Images Using the ImageIcon Class
Constructors and methods in the ImageIcon class
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Create an ImageIcon
– ImageIcon(Image img) - Creates ImageIcon from Image object
– ImageIcon(String filename) - Creates ImageIcon from file
– ImageIcon(URL url) - Creates ImageIcon from url
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Methods in the ImageIcon class
– int getIconHeight() - Gets height of ImageIcon object
– int getIconWidth() - Gets width of ImageIcon object
– void loadImage(Image img) - Loads image, returning when
load is complete
– void paintIcon(Component c, Graphics g, int x, int
y) - Paints the icon
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Create New Component to Display Image
Various components can display images
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Using the JLabel class
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JLabel(Icon icon)
JLabel(Icon icon, int hAlignment)
JLabel(String text, Icon icon, int hAlignment)
void setIcon(Icon icon)
Using the JButton class
– JButton(Icon icon)
– JButton(String text, Icon icon)
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Example Program
• Purpose: To demonstrate
– Use of an application program and
– Use of images in the graphical user interface
• Program:
– Class name: TextCompEx2Done
– Package name: widgetexs
– Project name: WidgetExs
• Questions:
– Can an image be replaced during runtime? If so, how?
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Example Program
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Printing C:\Documents and Settings\jgneal\My Documents\MyDev\MyJava\GuiDev\WidgetExs\src\widgetexs\TextCompEx2Done.java at 4/28/06
1 package
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7 import
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9 public class TextCompEx2Done extends JFrame implements ActionListener,
ItemListener {
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// Declare instance variables
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private
// Explanatory info for user
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private
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private
//JCheckBox for setting line wrap
// The JComboBox for font selection
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private
//JCheckBoxes for two font
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private
styles
// The JComboBox for font size selection
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private
// Display area for text
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private
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// The color defined by user
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private
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private int
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private int
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private
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private Font selectedFont = new Font(selectedFace, selectedStyle,
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private String fontNames[] = {
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private String fontSizes[] = {
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// The main method required for an application program
public static void main(String[] args) {
JFrame frame = new TextCompEx2Done
// Construct the window
frame.setSize(new Dimension
// Set its size
frame.setDefaultCloseOperation
frame.setVisible(true
// Make the window visible
}
public TextCompEx2Done() {
// Call parent constructor and set title in title bar of window
super
Container c = getContentPane
// Get reference to content pane
// Set layout for content pane
c.setLayout(new BorderLayout
JPanel jpan = new JPanel(new GridLayout
// Create JComboBoxes for user
selection of font and font size
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Printing C:\Documents and Settings\jgneal\My Documents\MyDev\MyJava\GuiDev\WidgetExs\src\widgetexs\TextCompEx2Done.java at 4/28/06
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editing
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jcboxFont = new JComboBox
jcboxFont.addItemListener(this
jpan.add
jcboxSize = new JComboBox
jcboxSize.setMaximumRowCount
jcboxSize.addItemListener(this
jpan.add
// Create JButton for user to choose text color
colorItem = new JButton
colorItem.addActionListener(this
jpan.add
// Create JCheckBox to enable user to line wrap on/off
linewrap = new JCheckBox("Line Wrap", false
linewrap.addItemListener(this
jpan.add
// Create JCheckBoxes for two font styles, but not as a group
fstyleBold = new JCheckBox("Bold", false
fstyleBold.addItemListener(this
jpan.add
fstyleItalic = new JCheckBox("Italic", false
fstyleItalic.addItemListener(this
jpan.add
c.add
// Get and display images for decorative purposes
URL url1 = this.getClass().getResource
JLabel jlabel1 = new JLabel(new ImageIcon
jlabel1.setBorder(new EtchedBorder
c.add
URL url2 = this.getClass().getResource
JLabel jlabel2 = new JLabel(new ImageIcon
jlabel2.setBorder(new EtchedBorder
c.add
// Create and add the JTextArea to be used for text display and
textArea = new JTextArea
textArea.setFont
textArea.setLineWrap(false
textArea.setBorder(new TitledBorder
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JScrollPane jspane = new JScrollPane
c.add
}
public void actionPerformed(ActionEvent e) {
if (e.getSource() == colorItem) {
Color returnedColor = JColorChooser.showDialog(this,
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if (returnedColor != null) {
textArea.setForeground
}
}
}
public void itemStateChanged(ItemEvent e) {
// If the JCheckBox for Bold style was clicked, set the applet's font
// style based on whether Bold was selected or deselected
if (e.getSource() == fstyleBold)
if (e.getStateChange() == ItemEvent.SELECTED)
else
if (e.getStateChange() == ItemEvent.DESELECTED)
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// If the JCheckBox for Italic style was clicked, set the
applet's font
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// style based on whether Italic was selected or deselected
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if (e.getSource() == fstyleItalic)
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if (e.getStateChange() == ItemEvent.SELECTED)
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else
if (e.getStateChange() == ItemEvent.DESELECTED)
// If the JCheckBox for line wrap was selected or not, set
// the JTextArea's line wrap accordingly
if (e.getSource() == linewrap)
if (e.getStateChange() == ItemEvent.SELECTED)
textArea.setLineWrap(true
else
if (e.getStateChange() == ItemEvent.DESELECTED)
textArea.setLineWrap(false
// If one of the items in the JComboBox was selected,
// set the fontname variable to the user's selection
if (e.getSource() == jcboxFont)
{
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Printing C:\Documents and Settings\jgneal\My Documents\MyDev\MyJava\GuiDev\WidgetExs\src\widgetexs\TextCompEx2Done.java at 4/28/06
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selectedFace = fontNames[jcboxFont.getSelectedIndex
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}
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if (e.getSource() == jcboxSize) {
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selectedSize = Integer.parseInt(fontSizes[jcboxSize.
getSelectedIndex
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}
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textArea.setFont(new Font(selectedFace, selectedStyle,
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}
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151 }
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Using Audio Clips
Methods in the Applet class
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Methods for using audio clips
– AudioClip getAudioClip(URL url) - Returns the AudioClip
object specified by the url; always returns immediately; data loaded
when attempt to play is made
– static AudioClip newAudioClip(URL url) - Returns the
AudioClip object specified by the url
Methods in the AudioClip interface class
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Methods for using audio clips
– void play() - Plays this audio clip starting from the beginning
– void loop() - Plays this audio clip in a loop starting at beginning
– void stop() - Stops playing this audio clip
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Example Program
• Purpose: To demonstrate
– Use of an applet program and
– Use of audio and images in the graphical user interface
• Program:
– Class name: FlagAnthem
– Package name: mediaexs
– Project name: MediaExs
• Code is available on instructor’s webpage
• Questions:
– What are some problems or shortcomings of this program?
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Example Program
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Timer Class
Purpose
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Has a specified delay time interval, and repeatedly fires an
action event once per time interval (e.g., once per second)
The delay time interval is the time between action events
For example, an animation object can use a Timer as the
trigger for drawing its frames
Setting up a Timer involves
1. Creating a Timer object,
2. Registering one or more action listeners on it, and
3. Starting the timer using the start method
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Timer Class
Selected constructors and methods
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Constructor
– Timer(int delay, ActionListener listener) - Creates
a Timer that will notify its listeners every delay milliseconds
•
Methods
– void setDelay(int delay) - Sets the Timer’s delay,
the number of milliseconds between successive action
events
– void start() - Starts the Timer, causing it to start
sending action events to its listeners
– void stop() - Stops the Timer, causing it to stop
sending action events to its listeners
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Example Program
• Purpose: To demonstrate
– Use of an application program and
– Use of a Timer object to implement animation
• Program:
– Class name: ApplicWTimer
– Package name: mymediaexs
– Project name: MyMediaExs
• Questions:
– How would you vary (e.g., slow down or speed up) the rate
at which the images appear to move across the applet?
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Example Program
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Printing C:\Documents and Settings\jgneal\My Documents\MyDev\MyJava\MyMedia\MyMediaExs\src\mymediaexs\ApplicWTimer.java at 4/28/06
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package
import
import
import
import
import
public class ApplicWTimer extends JFrame implements ActionListener {
private
private String fName[] = {"Assets.gif", "Contacts.gif", "Evtmgmt.
private
private
private
private
private
private
int
int
Image img[] = new
MediaTracker mt = new MediaTracker(this
private int
private int
private
private
private
private
private
private
int
int
int
int
int
Timer timer = new Timer(15, this
// The main method required for an application program
public static void main( String[] args ) {
// Construct the window
JFrame frame = new ApplicWTimer
frame.setDefaultCloseOperation
frame.setVisible( true
// Make the window visible
}
/** Creates a new instance of ApplicWTimer */
public ApplicWTimer() {
super
Container c = getContentPane
setSize( new Dimension
c.setLayout(new BorderLayout
setBackground
// Create a panel to display moving banner
imgPan = new ImagePanel
imgPan.setBorder(new EtchedBorder
imgPan.setBorder(new TitledBorder("Demonstration of Timer-Based
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Printing C:\Documents and Settings\jgneal\My Documents\MyDev\MyJava\MyMedia\MyMediaExs\src\mymediaexs\ApplicWTimer.java at 4/28/06
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c.add
timer.start
}
public void actionPerformed(ActionEvent e) {
imgPan.repaint
}
public class ImagePanel extends JPanel {
int
// Constructor
public ImagePanel(int w) {
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// Get images and assign into array
for (int
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img[i] = Toolkit.getDefaultToolkit().getImage
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try {
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mt.addImage
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mt.waitForID
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} catch (Exception ex) {
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System.out.println("\n" + ex.toString
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}
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}
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set image width and height variables
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imgWidth = img[0].getWidth(null
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imgHeight = img[0].getHeight(null
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setBackground
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setPreferredSize(new Dimension(apWidth, imgHeight + yPos *
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setVisible(true
}
// Paint the JPanel
public void paintComponent(Graphics g) {
super.paintComponent
int
int
// Create and draw image
while (xPos < panelWidth) {
g.drawImage(img[currentImgIndex], xPos, yPos, null
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}
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// Establish the horizontal start position for the next
repaint of banner
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// and the image with which to start
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if (startXPos > betweenSpace) {
102 /*
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106 */
if (startImageIndex < 0)
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if (startImgIndex >= fName.length)
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114 }
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}
} // End paintComponent
}
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