لطفا منتظر باشید ...
17.3 Playing Sounds with AudioClip
The sound capabilities of modern computer hardware are usually much
more advanced than the dumb terminals of yesterday, and typical users
expect their computers to make sounds that are prettier than the
coarse console bell. Java programs can do this by loading and playing
a file of audio data with the
java.applet.AudioClip interface. As the package name
implies, the AudioClip interface was originally
intended only for applets. Since Java 1.0, applets have been able to
call their getAudioClip( ) instance method to read
an audio file over the network. In Java 1.2, however, the static
java.applet.Applet.newAudioClip( ) method was
added to allow any application to read audio data from any URL
(including local file: URLs). This method and the
AudioClip interface make it very easy to play
arbitrary sounds from your programs, as demonstrated by Example 17-2.Invoke PlaySound with the URL of a sound file as
its sole argument. If you are using a local file, be sure to prefix
the filename with the file: protocol. The types of
sound files supported depend on the Java implementation.
Sun's default implementation supports
.wav, .aiff, and
.au files for sampled sound,
.mid files for MIDI, and even
.rmf files for the MIDI-related, proprietary
"Rich Music Format" defined by
Beatnik.[1]
[1] There is no guarantee that the
RMF format will
continue to be supported.
When you run the PlaySound class of Example 17-2, you may notice that the program never exits.
Like AWT applications, programs that use Java's
sound capabilities start a background thread and do not automatically
exit when the main( ) method returns.[2] To
make PlaySound better behaved, we need to
explicitly call System.exit( ) when the
AudioClip has finished playing. But this
highlights one of the shortcomings of the
AudioClip interface: it allows you to
play( ), stop( ), or
loop( ) a sound, but it provides no way to track
the progress of the sound or find out when it has finished playing.
To achieve that level of control over the playback of sound, we need
to use the JavaSound API, which we'll consider in
the next section.
[2] This is reported to be fixed in Java 1.5.
Example 17-2. PlaySound.java
package je3.sound;
/**
* Play a sound file from the network using the java.applet.Applet API.
*/
public class PlaySound {
public static void main(String[ ] args)
throws java.net.MalformedURLException
{
java.applet.AudioClip clip =
java.applet.Applet.newAudioClip(new java.net.URL(args[0]));
clip.play( );
}
}
17.3.1 Finding Music Files
Before you can test PlaySound,
you'll need some sound files to play. You probably
have lots of sampled audio files sitting around on your computer:
they are often bundled with operating systems and applications. Look
for files with .wav, .au,
or .aif extensions. You may not have MIDI files
on your computer, but many MIDI hobbyists make files available for
download on the Internet; a quick Internet search will locate many
samples you can use.The JavaSound web page is also worth a visit
(http://java.sun.com/products/java-media/sound/).
This page includes links to an interesting JavaSound demo application
that includes source code and its own set of sampled audio and
MIDI files. Also
of interest here are free downloadable MIDI soundbank files, which
may give you richer MIDI sound.
