Swing Hacks

Control iTunes Under Windows #83

Chapter 11, Native Integration and Packaging

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423

HACK

Compile this class along with the interfaces in the

test.jtunes

package. You

will also need the com4j.jar in your

CLASSPATH

and com4j.dll files in your

PATH. When you run the program, the com4j library will connect to

iTunes—launching it if necessary—and execute the

playPause( ) method.

com4j only allows you to call methods from the same thread

that you used to create the COM proxy. Typically, you want

to update your Swing components with iTunes information,

which you can do safely from the Swing event thread only.

This means that you should create the COM proxy from the

event thread as well (using the

ClassFactory method). Unfor-

tunately, this may cause your application to block for a few

seconds while iTunes loads (if it’s not already running). To

avoid this delay, you probably want to do all of your iTunes

communication through a custom queue, or use the new

concurrency utilities available in Java 5.0. The com4j devel-

opers are working on a solution to this problem, so it may be

solved by the time you read this.

Get Track Information

As with Apple Events on the Mac [Hack #82], the COM interface gives you a

way to query the currently playing track. You can call

iTunes.currentTrack( )

to get an IITTrack object. This object has methods to query just about any-

thing you could possible want to know about a track, including the artist,

album, playing time, encoding method, and even the import date. Each

method on the

IITTrack object returns information as Strings or Java primi-

tives, so it’s pretty easy to access anything you want and then stuff it into

your Swing interface. The following code shows how to get the track num-

ber, count, name, album, and artist:

IITTrack track;

track = itunes.currentTrack( );

int track_number = track.trackNumber( );

int track_count = track.trackCount( );

IiTunes itunes;

itunes = ClassFactory.createiTunesApp( );

itunes.playPause( );

} catch (Exception ex) {

System.out.println("exception : " + ex.getMessage( ));

ex.printStackTrace( );

}

}

}

Example 11-6. A listener to control iTunes on Windows (continued)