What is Multimedia?

1Liang, Introduction to Java Programming, Fifth Edition, (c) 2005 Pearson Education, Inc. All rights reserved. 0-13-148952-6

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.

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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) {}

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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.


Creating a URL from a Class ReferenceWhenever 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");


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.

Creating ImageIcon Using Absolute File Names


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);

Creating ImageIcon Using Class Reference


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);

Creating Image From ImageIcon


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.

Drawing Images in Graphics

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.


Displaying Image

Write a program that displays an image from /image/us.gif in the class directory on a panel.

DisplayImageDisplayImage RunRun


Case Study: ImageViewer Component

ImageViewerImageViewer

ImageViewer

-image: Image

-imageFilename: String

-stretched: boolean

-xCoordinate: int

-yCoordinate: int

+ImageViewer()

+ImageViewer(image: Image)

+createImage(imageFilename: String, object: Object): Image

+createImageIcon(imageFilename: String, object: Object): ImageIcon

+createImage(urlString: String): Image

+createImageIcon(urlString: String): ImageIcon

javax.swing.JPanel

Image in the image viewer.

Filename of the image.

True if the image is stretched in the viewer.

x-Coordinate of the upper left corner of the image in the viewer.

y-Coordinate of the upper left corner of the image in the viewer.

Constructs an image viewer with no image.

Constructs an image viewer with the specified image.

Creates an image from the specified image file. Creates an image icon from the specified image file.

Creates an image from the specified URL string.

Creates an image icon from the specified URL string.


Six Flag Example

Objective: Use the ImageViewer class to display six flags.

SixFlagsSixFlags RunRun


Case Study: Image Animation

Objective: Simulate a movie by displaying a sequence of images in a control loop.

ImageAnimationImageAnimation Run as an ApplicationRun as an Application


Creating AudioClip from an Audio FileTo 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);


Playing Audio

java.applet.AudioClip

+play()

+loop()

+stop()

Starts playing this audio clip. Each time this method is called, the clip is restarted from the beginning.

Plays the clip repeatedly.

Stops playing the clip.

To manipulate a sound for an audio clip, use the play(), loop(), and stop() methods in java.applet.AudioClip.


Playing Anthem Example

Objective: Display images and playing audio in applets and in applications.

FlagAnthemFlagAnthem

Run as an ApplicationRun as an Application


Packaging and Deploying Java Projects

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.

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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.


Viewing the Contents of a JAR FileYou can view the contents of a .jar file using

WinZip.


Manifest FileA 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.classJava-Bean: True Name: TioTacToe$Cell.classJava-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.


Running Archived Projects StandaloneThe 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: TicTacToeSealed: 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.


Running Archived Projects As AppletTo 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>


Pluggable Look-and-FeelThe pluggable look-and-feel feature lets you design a single set of GUI components that automatically has the look-and-feel 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

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Setting Look-And-FeelThe javax.swing.UIManager class manages the look-and-feel 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());


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.”

What is Multimedia?

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