function PrevNextListener(statusEvent) {
      this.statusEvent = statusEvent;
      this.statusEvent.updateStatus.subscribe(this.onStatusChange, this);
}

PrevNextListener.prototype.onStatusChange = function(type, args, me) {
	if (args[0].prevButtonEnabled) {
		prevButton.enable();
		var es = getEl('inputPrevButton').getChildrenByClassName('prevButton');
		if (es[0]) es[0].removeClass('prevButtonDisable');
	} else {
		prevButton.disable();
		var es = getEl('inputPrevButton').getChildrenByClassName('prevButton');
		if (es[0]) es[0].addClass('prevButtonDisable');
	}
	if (args[0].nextButtonEnabled) {
		nextButton.enable();
		var es = getEl('inputNextButton').getChildrenByClassName('nextButton');
		if (es[0]) es[0].removeClass('nextButtonDisable');
	} else {
		nextButton.disable();
		var es = getEl('inputNextButton').getChildrenByClassName('nextButton');
		if (es[0]) es[0].addClass('nextButtonDisable');
	}
}