Zoom mapview to a region where pins are dropped

Question

If I have 3 pins in a mapview, how will I zoom to these pins, when the map loads. That is, when the map loads I need to have a zoomed view, but the view should accomodate all pins dropped in the map. Its working, when the map has just one pin. But I cant handle zoom with multiple pins. Help needed

Answer 1

I wrote the below code in an App and it is similar to @ElanthiraiyanS Answer

-(void)zoomToFitMapAnnotations:(MKMapView*)mapView insideArray:(NSArray*)anAnnotationArray
{   
    // NSLog(@"%s", __FUNCTION__);
    if([mapView.annotations count] == 0) return;

    CLLocationCoordinate2D topLeftCoord;
    topLeftCoord.latitude = -90;
    topLeftCoord.longitude = 180;

CLLocationCoordinate2D bottomRightCoord;
bottomRightCoord.latitude = 90;
bottomRightCoord.longitude = -180;

for(MKPointAnnotation* annotation in anAnnotationArray)
{
    topLeftCoord.longitude = fmin(topLeftCoord.longitude, annotation.coordinate.longitude);
    topLeftCoord.latitude = fmax(topLeftCoord.latitude, annotation.coordinate.latitude);

    bottomRightCoord.longitude = fmax(bottomRightCoord.longitude, annotation.coordinate.longitude);
    bottomRightCoord.latitude = fmin(bottomRightCoord.latitude, annotation.coordinate.latitude);
}

MKCoordinateRegion region;
region.center.latitude = topLeftCoord.latitude - (topLeftCoord.latitude - bottomRightCoord.latitude) * 0.5;
region.center.longitude = topLeftCoord.longitude + (bottomRightCoord.longitude - topLeftCoord.longitude) * 0.5;
region.span.latitudeDelta = fabs(topLeftCoord.latitude - bottomRightCoord.latitude) * 1.1; // Add a little extra space on the sides
region.span.longitudeDelta = fabs(bottomRightCoord.longitude - topLeftCoord.longitude) * 1.1; // Add a little extra space on the sides

region = [mapView regionThatFits:region];
[mapView setRegion:region animated:YES];

}

Answer 2

The below method will do that,

- (void)zoomToFitMapAnnotations:(MKMapView *)mapView { 
    if ([mapView.annotations count] == 0) return; 

    CLLocationCoordinate2D topLeftCoord; 
    topLeftCoord.latitude = -90; 
    topLeftCoord.longitude = 180; 

    CLLocationCoordinate2D bottomRightCoord; 
    bottomRightCoord.latitude = 90; 
    bottomRightCoord.longitude = -180; 

    for(MapAnnotation *annotation in mapView.annotations) { 
        topLeftCoord.longitude = fmin(topLeftCoord.longitude, annotation.coordinate.longitude); 
        topLeftCoord.latitude = fmax(topLeftCoord.latitude, annotation.coordinate.latitude); 
        bottomRightCoord.longitude = fmax(bottomRightCoord.longitude, annotation.coordinate.longitude); 
        bottomRightCoord.latitude = fmin(bottomRightCoord.latitude, annotation.coordinate.latitude); 
    } 

    MKCoordinateRegion region; 
    region.center.latitude = topLeftCoord.latitude - (topLeftCoord.latitude - bottomRightCoord.latitude) * 0.5; 
    region.center.longitude = topLeftCoord.longitude + (bottomRightCoord.longitude - topLeftCoord.longitude) * 0.5;      
    region.span.latitudeDelta = fabs(topLeftCoord.latitude - bottomRightCoord.latitude) * 1.1; 

    // Add a little extra space on the sides 
    region.span.longitudeDelta = fabs(bottomRightCoord.longitude - topLeftCoord.longitude) * 1.1; 

    // Add a little extra space on the sides 
    region = [mapView regionThatFits:region]; 
    [mapView setRegion:region animated:YES]; 
}

Answer 3

you may calc the center of all pins

- (CLLocationCoordinate2D)centerPointFromAnnotationArray:(NSArray *)array
{
    CLLocationCoordinate2D coorMax = CLLocationCoordinate2DMake(0, 0);
    CLLocationCoordinate2D coorMin = CLLocationCoordinate2DMake(999, 999);

    for ( int i = 0 ; i < [array count] ; ++i )
    {
        LMPoint *a = [array objectAtIndex:i];

        if (  ( a.coordinate.latitude != 0.0f ) || ( a.coordinate.longitude != 0.0f ) )
        {
            if ( a.coordinate.latitude > coorMax.latitude )
            {
                coorMax.latitude = a.coordinate.latitude;
            }
            if ( a.coordinate.longitude > coorMax.longitude )
            {
                coorMax.longitude = a.coordinate.longitude;
            }
            if ( a.coordinate.latitude < coorMin.latitude )
            {
                coorMin.latitude = a.coordinate.latitude;
            }
            if ( a.coordinate.longitude < coorMin.longitude )
            {
                coorMin.longitude = a.coordinate.longitude;
            }
        }
    }

    CLLocationCoordinate2D coorCenter = CLLocationCoordinate2DMake((coorMax.latitude+coorMin.latitude)/2, (coorMax.longitude+coorMin.longitude)/2);

    return coorCenter;
}

then zoom at the point with a proper zoomlevel