Rectangle constructor
Implementation
Rectangle(Map<String, dynamic> nativeRect) {
this.x = nativeRect['x'] != null? nativeRect['x']*1.0 : null;
this.y = nativeRect['y'] != null? nativeRect['y']*1.0 : null;
this.width = nativeRect['width'] != null? nativeRect['width']*1.0 : null;
this.height = nativeRect['height'] != null? nativeRect['height']*1.0 : null;
}