Swing Hacks

Provide Audio Controls During Playback #78

Chapter 10, Audio

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405

HACK

Having provided these two implementations, it should be clear how you

would create an

EnumControlComponent. The EnumControl.getValues( ) method

returns a

String array that you would use as the model of an uneditable

JComboBox. You’d use getValue( ) to set one of these as the initial value, and

then on user events, you could pull out the

JComboBox’s selection and set the

EnumControl with setValue( ).

Check It Out!

The DataLineControlGUI shown in Example 10-15 is a simple JPanel that

contains a

JLabel with the name of the file to be played on the first line of a

GridBagLayout, and then control-name JLabels and factory-generated con-

trol widgets on each successive line. The sound is played by the

PCMFilePlayer, which was introduced as part of playing uncompressed

AIFFs and WAVs of arbitrary lengths

[Hack #76].

private void setSliderFromControl( ) {

// figure out value as percent of range

float offsetValue = control.getValue( ) - min;

float percent = 0.0f;

if (range != 0.0)

percent = offsetValue / range;

// apply that to SLIDER_RANGE

int sliderValue = (int) (percent * SLIDER_RANGE);

slider.setValue (sliderValue);

}

private void setControlFromSlider( ) {

// figure out slider percentage

float sliderPercentage =

(float) slider.getValue( ) / SLIDER_RANGE;

// figure out value for that percentage of range

float rangeOffset = sliderPercentage * range;

float newValue = rangeOffset + min;

control.setValue (newValue);

}

// ChangeListener implementation

public void stateChanged (ChangeEvent e) {

setControlFromSlider( );

}

}

Example 10-14. Swing widget for a JavaSound FloatControl (continued)

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Chapter 10, Audio

#78 Provide Audio Controls During Playback

HACK

Example 10-15. Creating an audio player with GUI controls

import javax.sound.sampled.*;

public class DataLineControlGUI extends JPanel {

PCMFilePlayer player;

JButton startButton;

public DataLineControlGUI (File f) {

super( );

try {

player = new PCMFilePlayer (f);

} catch (Exception ioe) {

add (new JLabel ("Error: " +

ioe.getMessage( )));

return;

}

DataLine line = player.getLine( );

// layout

// line 0: name

setLayout (new GridBagLayout( ));

GridBagConstraints gbc = new GridBagConstraints( );

gbc.gridy = 0;

gbc.fill = GridBagConstraints.HORIZONTAL;

gbc.gridwidth = 2;

gbc.anchor = GridBagConstraints.SOUTH;

add (new JLabel ("File: " +

player.getFile().getName( )), gbc);

// subsequent lines: controls

gbc.gridwidth = 1;

Control[] controls = line.getControls( );

for (int i=0; i<controls.length; i++) {

gbc.gridx = 0;

gbc.gridy++;

gbc.anchor = GridBagConstraints.EAST;

add (new JLabel(controls[i].getType().toString( )), gbc);

JComponent controlComp =

ControlComponentFactory.getComponentFor (controls[i]);

gbc.gridx = 1;

gbc.anchor = GridBagConstraints.WEST;

add (controlComp, gbc);

}

// now start playing

player.start( );

}

Provide Audio Controls During Playback #78

Chapter 10, Audio

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407

HACK

When run with a suitable audio file, the resulting GUI looks like

Figure 10-11. Note that it’s possible you might have other control widgets

(or an unsupported label for

EnumControls and CompoundControls) if Java-

Sound gives you different controls than it did when I wrote and ran this on

Java 1.4.2.

public static void main (String[] args) {

JFileChooser chooser = new JFileChooser( );

chooser.showOpenDialog(null);

File file = chooser.getSelectedFile( );

DataLineControlGUI demo =

new DataLineControlGUI (file);

JFrame f = new JFrame ("JavaSound control");

f.getContentPane( ).add (demo);

f.pack( );

f.setVisible(true);

}

}

Figure 10-11. JavaSound audio player with GUI controls

Example 10-15. Creating an audio player with GUI controls (continued)