Using the Media Classes - JavaFX 8: A Definitive Guide to Building Desktop, Mobile, and Embedded Java Clients - page 405

@Override
protected Node initView() {
final GridPane gp = new GridPane();
gp.setPadding(new Insets(10));
gp.setHgap(20);
RowConstraints middle = new RowConstraints();
RowConstraints outside = new RowConstraints();
outside.setVgrow(Priority.ALWAYS);
gp.getRowConstraints().addAll(outside, middle, outside);
return gp;
}
private void createEQInterface() {
final GridPane gp = (GridPane) getViewNode();
final MediaPlayer mp = songModel.getMediaPlayer();
createEQBands(gp, mp);
}
// To be continued...
}
Here we have the first portion of our new view. As with all of our custom AbstractView classes, we need to
override the initView method so that we can create and return the view's “root” node. The equalizer view eventually
shows the live audio spectrum above the equalizer controls. The GridPane is once again the natural choice for
displaying content that consists of several rows of nodes. The top row contains our spectrum display, the middle row
contains a set of labels identifying the center frequency of each EqualizerBand , and the bottom row consists of a
row of sliders to adjust the gain of each EqualizerBand . We therefore create two row constraints to control the sizing
behavior of these rows. Finally, the new GridPane instance is returned so that it can become the view's root node.
Because initView is called from the superclass constructor, it is called before the rest of EqualizerView 's
constructor runs. Therefore, by the time that createEQInterface is called in the constructor, initView will already
have completed. This is why we can call the getViewNode method in createEQInterface to retrieve the GridPane that
was just created in initView . The createEQInterface method also retrieves the current MediaPlayer instance from
songModel and passes them both to the createEQBands method, which creates the EqualizerBand instances and the
Slider controls that are used to manipulate the gain of each band. This method is shown in Listing 9-23.
Listing 9-23. Creating Equalizer Bands
private void createEQBands(GridPane gp, MediaPlayer mp) {
final ObservableList<EqualizerBand> bands =
mp.getAudioEqualizer().getBands();
bands.clear();
double min = EqualizerBand.MIN_GAIN;
double max = EqualizerBand.MAX_GAIN;
double mid = (max - min) / 2;
double freq = START_FREQ;