Continuous zooming with MKMapView?

Question

I am working with a MKMapView thats visible area (zoom level) is set with a slider. I set the visible area with a MKCoordinateRegion and setRegion:animated:.

The problem is that I don't seem to be able to get extremely precise control over the visible area. It's as if the latitude\longitude deltas snap to the default ~21 zoom levels provided by Google.

What I really want is similar to the behavior of the Map.app when pinching to zoom. It scales the view until the threshold for a new zoom level is reached, and then it renders the new map level.

Is there a simple way to access\emulate this behavior? How does it work?

Code I'm using:

MKCoordinateRegion region;
MKCoordinateSpan span;
CLLocationCoordinate2D center = {45.475969,-73.64095};
region.center = center;
span.latitudeDelta = 0.01;
span.longitudeDelta = 0.01;
region.span = span;

[mapView setRegion:region animated:TRUE];

If I use a delta of 0.01 or 0.013, I get the exact same map.

Yeah, overall setting the region like this works fine. I just can't seem to get high precision. It's like the deltas ceil\floor to the different "map levels". — Mike A, Jun 21 '11 at 21:47
Well the deltas have a threshold, so I'm not sure it's possible to 'force' a zoom level for a specific delta. — Pier-Olivier Thibault, Jun 21 '11 at 21:53
[This question](http://stackoverflow.com/questions/4724176/slight-zoom-on-mkcoordinateregion) and its answers may explain what's happening. — , Jun 21 '11 at 21:54
That's a great post. Still doesn't help solve this problem though. — Mike A, Jun 21 '11 at 22:37

score 2 · Accepted Answer · answered Jul 13 '11 at 06:57

2

The simple answer is that MapKit does not allow you to programatically set a zoom level other than the default 21 levels supplied by google. The region span you set will always "snap" to the closest one.

answered Jul 13 '11 at 06:57

Mike A

2,501
2
23
30

score 0 · Answer 2 · answered Feb 27 '16 at 13:21

You can set mapview's visibleMapRect to achieve continuous zooming. Following code shows how to zoom in 1 level (it's a subclass of a MKMapView so self is an instance of MKMapView).

MKMapRect visibleRect = self.visibleMapRect;
MKMapSize size = visibleRect.size;
CGFloat aspectRatio = size.width / size.height;
CGPoint center = CGPointMake(visibleRect.origin.x + size.width/2, visibleRect.origin.y + size.height/2);
CGFloat zoomedHeight = size.height / 2;  // By divide by 2, will zoom in exact 1 level
CGFloat zoomedWidth = zoomedHeight * aspectRatio;
visibleRect = MKMapRectMake(center.x - zoomedWidth/2, center.y - zoomedHeight/2, zoomedWidth, zoomedHeight);
self.visibleMapRect = visibleRect;

score 0 · Answer 3 · answered Jun 21 '11 at 14:08

0

Are you using setRegion:animated: ? http://developer.apple.com/library/ios/#documentation/MapKit/Reference/MKMapView_Class/MKMapView/MKMapView.html#//apple_ref/occ/instm/MKMapView/setRegion:animated:

answered Jun 21 '11 at 14:08

devictories

21
4

Of course, which is why I specified my use of `MKCoordinateRegion`. I updated my question to be more clear. – Mike A Jun 21 '11 at 21:27

Continuous zooming with MKMapView?

3 Answers3