Within a UICollectionViewCell, setRegion has no effect for a MKMapView - ios

Question

I have set up a simple MKMapView (it is intended just to display a location on the map and nothing more) within one cell of a section of a CollectionView and am unable to set its region using setRegion. The MKMapViewDelegate is correctly set to the UICollectionViewCell as shown by breakpoints being hit within all the delegate methods.
I first tried to set the region in the View Controller's cellForItemAtIndexPath but I'm guessing this is too early, i.e. before the map is loaded so nothing happens and it loads a default location in the middle of the ocean.
I have tried passing the CLCoordinateLocation2D from the view controller to a CLCoordinateLocation2D in the cell during cellForItemAtIndexPath to set the region within the cell but where is the appropriate place to set the region? In a ViewController it should be done in ViewDidAppear rather than ViewDidLoad or ViewWillAppear so that the map is loaded but I cannot find an equivalent event for a collectionviewcell. awakeFromNib is clearly too soon. I have tried using various mapView delegates such as:
- (void)mapView:(MKMapView *)mapView1
regionWillChangeAnimated:(BOOL)animated
{
MKCoordinateSpan span = {.latitudeDelta = 0.0025, .longitudeDelta = 0.0025};
MKCoordinateRegion adjustedRegion = [mapView1 regionThatFits:MKCoordinateRegionMakeWithDistance(coords, 200, 200)];
[mapView1 setRegion:adjustedRegion animated:YES];
}
which runs but again does not change the region. I have tried
- (void)mapViewDidFinishLoadingMap:(MKMapView *)mapView and
- (void)mapViewWillStartRenderingMap:(MKMapView *)mapView
which seemed the best bets but a breakpoint before and after the setRegion line shows the region is never updated to the region I'm setting it to. The events all should be at a time that the map is fully loaded so why does setRegion simply have no effect??
Cell h file:
#interface BasicsCollectionViewCell : UICollectionViewCell
#property (strong, nonatomic) IBOutlet MKMapView *mapView;
#property (nonatomic) CLLocationCoordinate2D coords;
#end
Cell m file:
#interface BasicsCollectionViewCell() <MKMapViewDelegate>
#end
#implementation BasicsCollectionViewCell
#synthesize mapView;
#synthesize coords;
- (void)mapView:(MKMapView *)mapView1
regionWillChangeAnimated:(BOOL)animated
{
MKCoordinateSpan span = {.latitudeDelta = 0.0025, .longitudeDelta = 0.0025};
MKCoordinateRegion adjustedRegion = [mapView1 regionThatFits:MKCoordinateRegionMakeWithDistance(coords, 200, 200)];
[mapView1 setRegion:adjustedRegion animated:YES];
}
And the relevant part of cellForItemAtIndexPath:
cell0 = (BasicsCollectionViewCell*)[collectionView dequeueReusableCellWithReuseIdentifier:#"BasicsCell" forIndexPath:indexPath];
CLLocationCoordinate2D coord = {.latitude = self.latitude, .longitude = self.longitude};
[cell0 setCoords:coord];
cell0.mapView.delegate = cell0;
MKCoordinateSpan span = {.latitudeDelta = 0.0025, .longitudeDelta = 0.0025};
MKCoordinateRegion adjustedRegion = [cell0.mapView regionThatFits:MKCoordinateRegionMakeWithDistance(coord, 200, 200)];
[cell0.mapView setRegion:adjustedRegion animated:YES];
return cell0;
EDIT:
If I put breakpoints in the following code before and after the setRegion line at the asterixed points...
- (void)mapViewWillStartRenderingMap:(MKMapView *)mapView
{
MKCoordinateSpan span = {.latitudeDelta = 0.0025, .longitudeDelta = 0.0025};
MKCoordinateRegion adjustedRegion = [mapView regionThatFits:MKCoordinateRegionMakeWithDistance(coords, 200, 200)];
*****[mapView setRegion:adjustedRegion animated:YES];
*****}
then the debugger gives the following at the first breakpoint:
po self.mapView.region
{
(latitude = -41.508575000000008, longitude = 174.19921900000011)
(latitudeDelta = 13.733789001832008, longitudeDelta = 59.305518116231042)
}
And the same at the breakpoint immediately after:
po self.mapView.region
{
(latitude = -41.508575000000008, longitude = 174.19921900000011)
(latitudeDelta = 13.733789001832008, longitudeDelta = 59.305518116231042)
}
While at both breakpoints, the following is the (correct) value of adjustedRegion:
po adjustedRegion
{
(latitude = -0.13506928037132482, longitude = 51.518398284912109)
(latitudeDelta = 0.0018087389042361623, longitudeDelta = 0.0058458603824931288)
}
So it is simply that either setRegion is being ignored for some reason or it’s overridden by something else. Any ideas which?

Answer 1

I have faced similar one, where map region was not changed. So I manually called mapView delegate method
- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated;
in - (void) viewDidAppear:(BOOL)animated of view controller.
- (void) viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
// Manually called delegate method to forcefully set region.
[self mapView:self.mapView regionDidChangeAnimated:YES];
}
In your case call this method right after when you set map region. From your above code for example in cellForItemAtIndexPath method. For example:
cell0 = (BasicsCollectionViewCell*)[collectionView dequeueReusableCellWithReuseIdentifier:#"BasicsCell" forIndexPath:indexPath];
CLLocationCoordinate2D coord = {.latitude = self.latitude, .longitude = self.longitude};
[cell0 setCoords:coord];
cell0.mapView.delegate = cell0;
MKCoordinateSpan span = {.latitudeDelta = 0.0025, .longitudeDelta = 0.0025};
MKCoordinateRegion adjustedRegion = [cell0.mapView regionThatFits:MKCoordinateRegionMakeWithDistance(coord, 200, 200)];
[cell0.mapView setRegion:adjustedRegion animated:YES];
[cell0.mapView setRegion:adjustedRegion animated:YES];
// Force call of delegate method
[self mapView:cell0.mapView regionDidChangeAnimated:YES];
return cell0;
Note:
Don't forgot to override regionDidChangeAnimated method in view controller.
- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated {
}