ThinhPhan/ZoomToFitMapAnnotations.md

## ZoomToFitMapAnnotations.md

      
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              ZoomToFitMapAnnotations.md
            
          
    I search a lot of questions and answers in SO. This is what i figure out.
The result I want is map can zoom out to fit all/some annotations INCLUDE user's location.
The basic steps are:

Calculate the min lat/long
Calculate the max lat/long
Create CLLocation objects for these two points
Calculate distance between points
Create region using center point between points and distance converted to degrees
Pass region into MapView to adjust
Use adjusted region to set MapView region

Approach 1: Use system functions - It's only fit annotations NOT INCLUDE user's location
For iOS 7 and above (Referring MKMapView.h):
// Position the map such that the provided array of annotations are all visible to the fullest extent possible. 
- (void)showAnnotations:(NSArray *)annotations animated:(BOOL)animated NS_AVAILABLE(10_9, 7_0);

Approach 2: This is the most answer on SO
- (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(id<MKAnnotation> 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;
    
    // Add a little extra space on the sides
    region.span.latitudeDelta = fabs(topLeftCoord.latitude - bottomRightCoord.latitude) * 1.1;
    region.span.longitudeDelta = fabs(bottomRightCoord.longitude - topLeftCoord.longitude) * 1.1;
    
    region = [mapView regionThatFits:region];
    [mapView setRegion:region animated:YES];
}

Approach 3:
And can modify it like this:
- (void)fitMapViewToAnnotationList {
    MKMapRect zoomRect = MKMapRectNull;
    for (id <MKAnnotation> annotation in _mapView.annotations) {
        MKMapPoint annotationPoint = MKMapPointForCoordinate(annotation.coordinate);
        MKMapRect pointRect = MKMapRectMake(annotationPoint.x, annotationPoint.y, 0.1, 0.1);
        if (MKMapRectIsNull(zoomRect)) {
            zoomRect = pointRect;
        } else {
            zoomRect = MKMapRectUnion(zoomRect, pointRect);
        }
    }
    [_mapView setVisibleMapRect:zoomRect edgePadding:UIEdgeInsetsMake(10, 10, 10, 10) animated:YES];
}