ios MKMapView 添加遮盖层

项目中涉及到运动轨迹，不希望别人看到自己的运动轨迹时可以隐藏地图的底图。

使用MKPolygon可以在MKMapView上添加遮盖层，尝试添加一个覆盖全世界的polygon失败，猜想可能是因为东经180度和西经180度在地球上是同一条线所以添加失败，因此使用两个polygon来覆盖全球。

funccreatePolygon1() ->MKPolygon{

// render whole map view for map hidden

letpoint1 =CLLocationCoordinate2D(latitude:-90, longitude:0)

letpoint2 =CLLocationCoordinate2D(latitude:-90, longitude:180)

letpoint3 =CLLocationCoordinate2D(latitude:90, longitude:180)

letpoint4 =CLLocationCoordinate2D(latitude:90, longitude:0)

letpoints = [point1, point2, point3, point4]

returnMKPolygon(coordinates: points, count: points.count)

}

funccreatePolygon2() ->MKPolygon{

// render whole map view for map hidden

letpoint1 =CLLocationCoordinate2D(latitude:-90, longitude:-180)

letpoint2 =CLLocationCoordinate2D(latitude:-90, longitude:0)

letpoint3 =CLLocationCoordinate2D(latitude:90, longitude:0)

letpoint4 =CLLocationCoordinate2D(latitude:90, longitude:-180)

letpoints = [point1, point2, point3, point4]

returnMKPolygon(coordinates: points, count: points.count)

}