Transcript document

Optional
What is Multimedia?
Multimedia is a broad term that encompasses making, storing,
retrieving, transferring, and presenting various types of information,
such as text, graphics, pictures, videos, and sound. Multimedia
involves a complex weave of communications, electronics, and
computer technologies. It is beyond the scope of this book to cover
multimedia in great detail. This chapter concentrates on the
presentation of multimedia in Java.
Whereas most programming languages have no built-in multimedia
capabilities, Java was designed with multimedia in mind. It provides
extensive built-in support that makes it easy to develop powerful
multimedia applications. Java's multimedia capabilities include
animation that uses drawings, audio, and images.
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
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Optional
The URL Class
Audio and images are stored in files. The java.net.URL class can be
used to identify the files on the Internet. In general, a URL (Uniform
Resource Locator) is a pointer to a "resource" on the World Wide
Web. A resource can be something as simple as a file or a directory.
You can create a URL object using the following constructor:
public URL(String spec) throws MalformedURLException
For example, the following statement creates a URL object for
http://www.sun.com:
try {
URL url = new URL("http://www.sun.com");
}
catch(MalformedURLException ex) {
}
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Creating a URL for Local Files
The following statement creates a URL object for the file
c:\book\image\us.gif.
try {
URL url = new URL("c:\\book\\image\\us.gif");
}
catch(MalformedURLException ex) {
}
The preceding statement creates a URL for the absolute file name
c:\book\beep.au on the Windows. There are two problems: (1) the file
location is fixed; (2) it is platform-dependent. To circumvent these
problems, you can create the URLs for files using through the
resource of the class file using the java.lang.Class class.
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Creating a URL from a Class Reference
Whenever the Java Virtual Machine loads a class or an interface, it creates an
instance of a special class named Class. The Class class provides access to useful
information about the class, such as the data fields and methods. It also contains the
getResource(filename) method, which can be used to obtain the URL of a given file
name in the same directory with the class or in its subdirectory. As discussed in
Section 8.4.5, “The getClass Method,” you can obtain the class for the object at
runtime. Thus, you can use the following code to get the URL of a file:
Class class = this.getClass();
URL url = class.getResource(filename);
where filename is a relative file name in the same directory or a subdirectory of the
class. Suppose you run a class stored in c:\book, the following statement creates a
URL object for c:\book\image\us.gif.
URL url = this.getClass().getResource(“image\us.gif");
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Creating ImageIcon Using Absolute File Names
You used the ImageIcon class to create an icon from an image file
and the setIcon method or the constructor to place the image in a
GUI component, such as a button and a label. For example, the
following statements create an ImageIcon and set it on an JLabel
object jlbl.
ImageIcon imageIcon = new ImageIcon("c:\\book\\image\\us.gif");
//ImageIcon imageIcon = new ImageIcon("image/us.gif");
jlbl.setIcon(imageIcon);
This approach suffers a problem. The file location is fixed since it
uses the absolute file path on Window. Thus, the program cannot
run on other platforms and cannot run as applet.
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Creating ImageIcon Using Class Reference
To circumvent this problem, you can create the URLs for
files through the class reference using the java.lang.Class
class. For example, suppose the class file is in c:\book, the
following statements create a URL for
c:\book\image\us.gif.
Class class = this.getClass();
URL url = class.getResource("image/us.gif");
You can now create an ImageIcon using
ImageIcon imageIcon = new ImageIcon(url);
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Creating Image From ImageIcon
An image icon displays a fixed-size image. To display an
image in a flexible size, you need to use the
java.awt.Image class. An image can be created from an
image icon as follows:
Image image = imageIcon.getImage();
Given an Image, you can create an ImageIcon using
ImageIcon imageIcon = new ImageIcon(image);
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Drawing Images in Graphics
Using a label as an area for displaying images is simple and convenient, but you
don't have much control over how the image is displayed. A more flexible way to
display images is to use the drawImage method of the Graphics class on a panel
using one of the foure overloaded drawImage method.
drawImage(Image img, int x, int y, Color bgcolor,
ImageObserver observer)
drawImage(Image img, int x, int y, ImageObserver observer)
drawImage(Image img, int x, int y, ImageObserver observer)
drawImage(Image img, int x, int y, int width, int height,
Color bgcolor, ImageObserver observer)
ImageObserver is an asynchronous update interface that receives notifications of
image information as the image is constructed. The Component class implements
ImageObserver. Therefore, every GUI component is an instance of ImageObserver.
To draw images using the drawImage method in a Swing component, such as
JPanel, override the paintComponent method to tell the component how to display
the image in the panel.
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Displaying Image
Write a program that displays an image from
/image/us.gif in the class directory on a panel.
DisplayImage
Run
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
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Case Study: ImageViewer Component
javax.swing.JPanel
ImageViewer
-image: Image
Image in the image viewer.
-imageFilename: String
Filename of the image.
-stretched: boolean
True if the image is stretched in the viewer.
-xCoordinate: int
x-Coordinate of the upper left corner of the image in the viewer.
-yCoordinate: int
y-Coordinate of the upper left corner of the image in the viewer.
+ImageViewer()
Constructs an image viewer with no image.
+ImageViewer(image: Image)
Constructs an image viewer with the specified image.
+createImage(imageFilename:
String, object: Object): Image
Creates an image from the specified image file.
+createImageIcon(imageFilename:
String, object: Object): ImageIcon
Creates an image icon from the specified image file.
+createImage(urlString: String):
Image
Creates an image from the specified URL string.
+createImageIcon(urlString:
String): ImageIcon
Creates an image icon from the specified URL string.
ImageViewer
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Six Flag Example
Objective: Use the
ImageViewer class
to display six flags.
SixFlags
Run
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Case Study: Image Animation
 Objective:
Simulate a movie by displaying a sequence
of images in a control loop.
ImageAnimation
Run as an Application
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Creating AudioClip from an Audio File
To play an audio file in an applet, first create an audio clip object for
the audio file. The audio clip is created once and can be played
repeatedly without reloading the file. To create an audio clip, use the
static method newAudioClip() in the java.applet.Applet class:
AudioClip audioClip = Applet.newAudioClip(url);
Audio was originally used with Java applets. For this reason, the
AudioClip interface is in the java.applet package.
The following statements, for example, create an AudioClip for the
beep.au audio file in the same directory with the class you are running.
Class class = this.getClass();
URL url = class.getResource("beep.au");
AudioClip audioClip = Applet.newAudioClip(url);
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Playing Audio
java.applet.AudioClip
+play()
Starts playing this audio clip. Each time this method is called, the clip is
restarted from the beginning.
+loop()
Plays the clip repeatedly.
+stop()
Stops playing the clip.
To manipulate a sound for an audio clip, use the play(), loop(), and
stop() methods in java.applet.AudioClip.
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Playing Anthem Example
Objective: Display
images and playing
audio in applets
and in applications.
FlagAnthem
Run as an Application
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Packaging and Deploying
Java Projects
Optional
What is JAR?
Java archive file can be used to group all the project files in a
compressed file for deployment.
The Java archive file format (JAR) is based on the popular ZIP file
format.
This single file can be deployed on an end-user’s machine as an
application. It also can be downloaded to a browser in a single HTTP
transaction, rather than opening a new connection for each piece. This
greatly simplifies application deployment and improves the speed
with which an applet can be loaded onto a web page and begin
functioning.
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Creating JAR
You can use the JDK jar command to create an
archive file. The following command creates an
archive file named TicTacToe.jar for classes
TicTacToe.class and TicTacToe$Cell.class.
jar -cf TicTacToe.jar TicTacToe.class TicTacToe$Cell.class
The -c option is for creating a new archive file, and
the -f option specifies the archive file’s name.
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Viewing the Contents of a JAR File
You can view the contents of a .jar file using
WinZip.
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Manifest File
A manifest file was created with the path name meta-inf\. The
manifest is a special file that contains information about the files
packaged in a JAR file. For instance, the manifest file in
TicTacToe.jar contains the following information:
Manifest-Version: 1.0
Name: TicTacToe.class
Java-Bean: True
Name: TioTacToe$Cell.class
Java-Bean: True
You can modify the information contained in the manifest file to
enable the JAR file to be used for a variety of purposes. For instance,
you can add information to specify a main class to run an application
using the .jar file.
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Running Archived Projects Standalone
The manifest file must have an entry to contain the main class. For
example, to run TicTacToe, you need to insert the following two lines
in the manifest file:
Main-Class: TicTacToe
Sealed: true
Run the .jar file using the java command from the directory that
contains TicTacToe.jar,
java -jar TicTacToe.jar
TIP: You can write an installation procedure that creates the necessary
directories and subdirectories on the end-user’s computer. The
installation can also create an icon that the end-user can double-click
on to start the program. For information on creating Windows desktop
icon, please see www.prenhall.com/liang/intro5e.html.
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Running Archived Projects As Applet
To run TicTacToe as an applet, modify the <APPLET> tag
in the HTML file to include an ARCHIVE attribute. The
ARCHIVE attribute specifies the archive file in which the
applet is contained. For example, the HTML file for
running TicTacToe can be modified as shown below:
<APPLET
CODE = "TicTacToe.class"
ARCHIVE = "TicTacToe.jar"
WIDTH = 400
HEIGHT = 300
HSPACE = 0
VSPACE = 0
ALIGN = Middle
>
</APPLET>
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Optional
Pluggable Look-and-Feel
The pluggable look-and-feel feature lets you design a single
set of GUI components that automatically has the look-andfeel of any OS platform. The implementation of this feature
is independent of the underlying native GUI, yet it can
imitate the native behavior of the native GUI.
Currently, Java supports the following three look-and-feel
styles:
·
·
·
Metal
Motif
Windows
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Setting Look-And-Feel
The javax.swing.UIManager class manages the look-andfeel of the user interface. You can use one of the following
three methods to set the look-and-feel for Metal, Motif, or
Windows:
UIManager.setLookAndFeel
(UIManager.getCrossPlatformLookAndFeelClassName());
UIManager.setLookAndFeel
(new com.sun.java.swing.plaf.motif.MotifLookAndFeel());
UIManager.setLookAndFeel
(new com.sun.java.swing.plaf.windows.WindowsLookAndFeel());
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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Setting Look-And-Feel in Static
Initialization Block
To ensure that the setting takes effect, the setLookAndFeel method
should be executed before any of the components are instantiated.
Thus, you can put the code in a static block, as shown below:
static {
try {
// Set a look-and-feel, e.g.,
//UIManager.setLookAndFeel
// (UIManager.getCrossPlatformLookAndFeelClassName());
}
catch (UnsupportedLookAndFeelException ex) {}
}
Static initialization blocks are executed when the class is loaded. For
more information on static initialization blocks, please refer to
Section 8.12, “Initialization Block.”
Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All
rights reserved. 0-13-148952-6
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