Polymorphism - Java Software Solutions: Foundations of Program Design - page 531

LISTING 10.16 continued

//--------------------------------------------------------------
// Gets the value of each slider, then updates the labels and
// the color panel.
//--------------------------------------------------------------
public void stateChanged (ChangeEvent event)
{
red = rSlider.getValue();
green = gSlider.getValue();
blue = bSlider.getValue();

rLabel.setText ("Red: " + red);
gLabel.setText ("Green: " + green);
bLabel.setText ("Blue: " + blue);

colorPanel.setBackground ( new Color (red, green, blue));
}
}
}

constructor specifies the slider's initial value. In our example, the initial value of
each slider is zero, which puts the slider knob to the far left when the program
initially executes.
The panel called colorPanel is used to display the color specified by the sliders
by setting its background color. Initially, the settings of the sliders are all zero,
which correspond to the initial color displayed (black).
The JSlider class has several methods that allow the programmer to tailor
the look of a slider. Major tick marks can be set at specific intervals using the
setMajorTickSpacing method. Intermediate minor tick marks can be set using
the setMinorTickSpacing method. Neither is displayed, however, unless the
setPaintTicks method, with a parameter of true , is invoked as well. Labels
indicating the value of the major tick marks are displayed if indicated by a call to
the setPaintLabels method.
Note that in this example, the major tick spacing is set to 50. Starting at zero,
each increment of 50 is labeled. The last label is therefore 250, even though the
slider value can reach 255.