Fitting all map annotations for display iOS

If you support iOS4+, use the method of creating a MKMapRect to display

MKMapRect zoomRect = MKMapRectNull;

if ([mView.annotations count] == 0) return;

NSInteger count=0;

for (id <MKAnnotation> annotation in mapView.annotations){

if( [annotation isKindOfClass:[MapViewAnnotation class]] && annotation.coordinate.latitude != 0 && annotation.coordinate.longitude != 0 ){

MKMapPoint annotationPoint = MKMapPointForCoordinate(annotation.coordinate);

MKMapRect pointRect = MKMapRectMake(annotationPoint.x, annotationPoint.y, 0, 0);

if (MKMapRectIsNull(zoomRect)) {

zoomRect = pointRect;

}

else {

zoomRect = MKMapRectUnion(zoomRect, pointRect);

}

count++;

}

}

MKCoordinateRegion region = MKCoordinateRegionForMapRect(zoomRect);

[mapView setRegion:region];

If you need to support iOS3, loop through the annotations to find the top left and bottom most right annotation to figure out largest region to display:

CLLocationCoordinate2D topLeftCoord; 

    topLeftCoord.latitude = -90; 

    topLeftCoord.longitude = 180; 

    CLLocationCoordinate2D bottomRightCoord; 

    bottomRightCoord.latitude = 90; 

    bottomRightCoord.longitude = -180; 

NSInteger i=0;

    for(MapViewAnnotation *annotation in mView.annotations) { 

if(

  ([annotation isKindOfClass:[MapViewAnnotation class]] || [annotation isKindOfClass:[MKPointAnnotation class]] == includeKml) 

  && (![annotation isKindOfClass:[MKUserLocation class]])

  ){

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); 

i++;

}

    } 

    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 = [mView regionThatFits:region]; 

    [mView setRegion:region animated:YES];