Java Reference
In-Depth Information
public function isPlaying():Boolean{
return soundHelper.isPlaying();
}
}
In Listing 9-4 we can see the class
SoundPlayer
. The class
SoundPlayer
is intended to wrap a
SoundHelper
and provide a JavaFX-style interface to any application that requires the feature of
SoundHelper
. We can see
SoundPlayer
implements the interface
Observer
and thus has an
update
function. It is very simple for JavaFX classes to extend Java interfaces; the only real difference is in the
syntax of declaring the function. In the
init
function, we can see that
SoundPlayer
creates a new
SoundHelper
and then registers itself as an observer. Now any time the levels change in the
SoundHelper
,
the update function of
SoundPlayer
will be called.
Looking at the update function of
SoundPlayer
, we can see that the levels in
SoundHelper
are copied
into the sequence
levels
of class
SoundPlayer
. But notice that the
for
loop that does the copying is
actually performed in a function that is passed the static function
FX.deferAction
. The function
FX.deferAction
is a utility function that causes any function passed into it to be called by the JavaFX
event thread. This is important because this allows other JavaFX objects to bind to the sequence
levels
in a reliable way.
In fact,
SoundPlayer
has a number of other variables, which are bound to
levels
such as
hiChannels
,
midChannels
, and
lowChannels
. These variables are simply aggregates of the values in
levels
and will be
used later to allow audio visualization to bind to just the high, middle, or low parts of the song.
SoundPlayer
also has a number of functions that simply wrap methods on the
soundHelper
; this is
done to make
SoundPlayer
a complete package and prevents developers who use
SoundPlayer
from
needing to know anything about
SoundHelper
and the whole Java side of things.
One last thing to note is how simple it is for JavaFX classes to make calls to Java objects. On the
JavaFX side, the Java object is created as normal, and method calls are made just like they were native
JavaFX objects. Calling JavaFX functions from Java is a bit trickier; there are particulars with the
differences in JavaFX primitive types and Java's primitive types that can confound any developer. The
trick here was to have the JavaFX class implement a Java interface that ensures that the types used in the
function calls are going to be familiar from the Java perspective.
Audio Visualizations
Now that we have a nice JavaFX interface for our sound processing code, we can start using
SoundPlayer
in an example application that will illustrate how easy it is to create compelling audio visualizations in
JavaFX. Figure 9-1 shows the sample application we will be talking about.
In Figure 9-1 we can see scene composed of a control for starting and pausing the music, as well as a
control bar where we can change which part of the song is playing. There are also three check boxes that
control which three of our example effects are displayed. In this screenshot, all three are displayed. Let's
start by looking at
Main.fx
and how this example was set up (Listing 9-5).
Listing 9-5.
Main.fx
var soundPlayer = SoundPlayer{
url: "{__DIR__}media/01 One Sound.mp3";
}
var bars = Bars{
translateX: 50
