Resize MKMapView - objective-c

Question

Looks like simple task. But when I try to resize using setFrame method I got glitches. There are some other UIViews resized using setFrame method and it works perfectly. I made custom application with slider bar and map view. SlideBar changes X position for MKMapView, but keeps width equals to screen width. This approach works fine for all Views. But MKMapView resizes with smooth troubles. Can anyone please give a clue why it's happening and how to solve it?

Answer 1

I had the same problem, which seems to occur only on iOS 6 (Apple Maps) and not on iOS 5 (Google Maps).
My solution was to take a "screenshot" of the map when the user start dragging the divider handle, replace the map with this screenshot during the drag, and put the map back when the finger is released.
I used the code from How to capture UIView to UIImage without loss of quality on retina display for UIView screenshot and Nikolai Ruhe's answer at How do I release a CGImageRef in iOS for a nice background color.
My UIPanGestureRecognizer action is something like this (the (MKMapView)self.map is a subview of (UIView)self.mapContainer with autoresizing set on Interface Builder):
- (IBAction)handleMapPullup:(UIPanGestureRecognizer *)sender
{
CGPoint translation = [sender translationInView:self.mapContainer];
// save current map center
static CLLocationCoordinate2D centerCoordinate;
switch (sender.state) {
case UIGestureRecognizerStateBegan: {
// Save map center coordinate
centerCoordinate = self.map.centerCoordinate;
// Take a "screenshot" of the map and set the size adjustments
UIImage *mapScreenshot = [UIImage imageWithView:self.map];
self.mapImage = [[UIImageView alloc] initWithImage:mapScreenshot];
self.mapImage.autoresizingMask = self.map.autoresizingMask;
self.mapImage.contentMode = UIViewContentModeCenter;
self.mapImage.clipsToBounds = YES;
self.mapImage.backgroundColor = [mapScreenshot mergedColor];
// Replace the map with a screenshot
[self.map removeFromSuperview];
[self.mapContainer insertSubview:self.mapImage atIndex:0];
} break;
case UIGestureRecognizerStateChanged:
break;
default:
// Resize the map to the new dimension
self.map.frame = self.mapImage.frame;
// Replace the screenshot with the resized map
[self.mapImage removeFromSuperview];
[self.mapContainer insertSubview:self.map atIndex:0];
// Empty screenshot memory
self.mapImage = nil;
break;
}
// resize map container according do the translation value
CGRect mapFrame = self.mapContainer.frame;
mapFrame.size.height += translation.y;
// reset translation to make a relative read on next event
[sender setTranslation:CGPointZero inView:self.mapContainer];
self.mapContainer.frame = mapFrame;
self.map.centerCoordinate = centerCoordinate; // keep center
}