Swing Hacks

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Chapter 10, Audio

#73 Play a Sound with QuickTime for Java

HACK

example, if the media could play in both directions and you wanted to be

notified when it reached the beginning of the movie too, you’d pass

StdQTConstants.triggerAtStop | StdQTConstants.triggerAtStart

.

Next, you have to use

callMeWhen( )

to register the callback. This signs you

up for one callback—if you’re called and are still interested in future events,

you have to reregister with another

callMeWhen( )

.

When the sound finishes, the callback calls

execute( ). This is when you shut

everything down, as in the other hacks. Notice that you close down Quick-

Time with

QTSession.close( ), the obvious counterpart to QTSession.open( ).

There are some issues about how well it works on Windows: it sometimes

hangs for me, and you may want to use the safer

QTSession.exitMovies( ),

which only closes down some of QTJ, but the rest seems to get taken care of

by QTJ itself, as I’ve never had a problem.

And one more bit of arcane QTJ lore: the code makes a call to

TaskAllMovies.addMovieAndStart( ). This helps deal with the fact that mov-

ies have to explicitly be given CPU time, with calls to a

task( ) method, in

order to work.

TaskAllMovies is a convenience Thread that can periodically

make this tasking call for all your movies. If you’ve read Chris’ book on

QTJ, you would think that this isn’t necessary, as having the AWT event-

dispatch thread usually provides tasking calls. The problem is that the dia-

log box that’s showing while the audio plays is modal; thus, it blocks the

event loop, which in turn blocks the tasking you usually get for free with

AWT. So, you have to set it up yourself.

QTJ is full of weird gotchas like this. What do you expect

when it’s largely a port from C?

Compiling QuickTime Code

Yep, this hack has special compile instructions. First, you have to be sure

that your machine even has QuickTime for Java on it. It’s installed by

default with Mac OS X, so this is only an issue for Windows-based develop-

ers. On Windows, if you don’t have QuickTime at all, get it from http://

www.apple.com/quicktime/ and do a custom install: QuickTime for Java will

be one of the non-default optional pieces, and you just need to checkmark it

to include it in your install. If you do have QuickTime, run the QuickTime

Updater from your Start menu or your tray to do a “custom” update, which

will show the same list of optional pieces as the main installer.

Play a Sound with QuickTime for Java #73

Chapter 10, Audio

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375

HACK

The install or update will put QTJava.zip into the lib/ext of any Java home

folders it finds. It should also put a copy in C:\windows\system32 and add a

system-wide environment variable

QTJAVA

pointing to one of these files, with

the path in quotes (which may or may not be good for you, depending on

what else you do with environment variables).

Here’s the fun part about compiling: you must explicitly point your compile-

time classpath to one of these QTJava.zip files for

javac (or jikes, or what-

ever) to find the QTJ classes. If you don’t, you’ll get a bunch of compile-

time errors like:

QTJSound.java:4: package quicktime.std does not exist

import quicktime.std.*;

^

QTJSound.java:5: package quicktime.std.clocks does not exist

import quicktime.std.clocks.*;

^

QTJSound.java:6: package quicktime.std.movies does not exist

import quicktime.std.movies.*;

So, assuming you want to work with a copy of Java installed in Program

Files\Java\j2re1.4.2_06 (which is my current path…yours may vary), you

compile this demo with the following command:

C:\>javac

-classpath "c:\Program Files\Java\j2re1.4.2_06\lib\ext\QTJava.zip"

QTJSound.java

This should be typed as one line—I’ve word-wrapped to

accommodate the book’s margins.

You can substitute any other path to a QTJava.zip file for the classpath if

you find it more convenient, or just write an Ant build file to automate

everything for you.

On Mac OS X, the location of QTJava.zip is never a mystery because the sys-

tem installer puts it in /System/Library/Java/Extensions.QTJava.zip. So, you

compile with:

[aeris:HacksBook/Media/52] cadamson% javac -classpath

/System/Library/Java/Extensions/QTJava.zip

QTJSound.java

In either case, you’ll probably be relieved to know that you don’t have to

specify the classpath when running a QTJ application.