Question

based on the volume knob from this example, http://fxexperience.com/2012/01/fun-javafx-2-0-audio-player/

How would you make a volume knob that snaps to particular angle value, every 15 or 30 degree for example ? Thanks for any hint.
What i did is redefine rotateKnob in subclass and set the angle in this manner for the slider to snap at values 180, 120, 60, 0, -180, -160, -120, -60 :

Slider s = getSkinnable();
    double zeroOneValue = (s.getValue() - s.getMin()) / (s.getMax() - s.getMin());
    double angle = minAngle + ((maxAngle - minAngle) * zeroOneValue);

    int angleMod = (int) (angle % 60);
    double val;
    if (angleMod == 0) {
        val = (int) angle;
    } else if (angleMod > (60 / 2)) {
        val = (int) angle - angleMod;
    } else {
        val = (int) angle - angleMod + 60;
    }

Answer 1

You don’t need to do anything special. Just make use of the “snapToTicks” property. In the main class, after the volume knob is defined, put this code:

    volumeKnob.setMinorTickCount(0);
    volumeKnob.setMajorTickUnit(1.0/14.0);
    volumeKnob.snapToTicksProperty().set(true);

The numbers here are based on the fact that there are 14 “dots” around the volume knob. This code will make sure that you can only set the volume to one of those dots.