JLabel labelLength, JLabel labelDuration) {
super(positionsModel);
this.labelLength = labelLength;
this.labelDuration = labelDuration;
lengthCalculator.addLengthCalculatorListener(new LengthCalculatorListener() {
public void calculatedDistance(final int meters, final int seconds) {
invokeLater(new Runnable() {
public void run() {
updateLabel(meters, seconds);
}