当用户移动map时调用以下函数。可以获取视口(viewport)吗？视口(viewport)是北/东和纬度的纬度和经度。和隆。南/西。funcmapView(mapView:MKMapView,regionDidChangeAnimatedanimated:Bool){print("The\(mapView.centerCoordinate)")print("themaprect\(mapView.visibleMapRect.origin)")print("themaprect\(mapView.visibleMapRect.size)")//Ifindjustthisattribu