feature.getGeometry().on(
            'propertychange',
            function(propEvt) {
                console.log('I'm here');
                var extent = feature.getGeometry().getExtent();
                var centerOfFeature = getCenterOfExtent(extent);
                popup.setPosition(centerOfFeature);
            },
            feature.getGeometry());

feature.on('change',function(e){
 console.log('Im here');
 var extent = feature.getGeometry().getExtent();
 var centerOfFeature = getCenterOfExtent(extent);
 popup.setPosition(centerOfFeature);
});