有沒有辦法讓mkmapview放大顯示所有註釋？

Question

有沒有辦法讓mkmapview放大顯示所有註釋？我在北美有94個註釋，我不希望用戶必須縮小很多。以下是我的代碼片段：

- (void)viewDidLoad { 
    [super viewDidLoad]; 

    [mapView setMapType:MKMapTypeStandard]; 
    [mapView setZoomEnabled:YES]; 
    [mapView setScrollEnabled:YES]; 




    // Central Alabama Chapter 

    MKCoordinateRegion region = { {0.0, 0.0 }, { 0.0, 0.0 } }; 
    region.center.latitude = 33.45606; 
    region.center.longitude = -86.83078; 
    region.span.longitudeDelta = 0.01f; 
    region.span.latitudeDelta = 0.01f; 

    [mapView setRegion:region animated:YES]; 

    [mapView setDelegate:self]; 

    DisplayMap *ann = [[DisplayMap alloc] init]; 
    ann.title = @"Central Alabama Chapter"; 
    ann.subtitle = @"721 Hillmoor Lane Homewood, Alabama 35209"; 
    ann.coordinate = region.center; 
    [mapView addAnnotation:ann]; 


    // Walnut Ridge Fire Department 

    MKCoordinateRegion region1 = { {0.0, 0.0 }, { 0.0, 0.0 } }; 
    region1.center.latitude = 36.11493; 
    region1.center.longitude = -90.95695; 
    region1.span.longitudeDelta = 0.01f; 
    region1.span.latitudeDelta = 0.01f; 



    DisplayMap *ann1 = [[DisplayMap alloc] init]; 
    ann1.title = @"Walnut Ridge Fire Department"; 
    ann1.subtitle = @"3217 Highway 67 # B, Walnut Ridge, AR"; 
    ann1.coordinate = region1.center; 
    [mapView addAnnotation:ann1]; 

Answer 1

double minLat=360.0f,minLon=360.0f; 
double maxLat=-360.0f,maxLon=-360.0f; 

for (<MKAnnotation> vu in [theMapView annotations]) { 
    if (vu.coordinate.latitude < minLat) minLat = vu.coordinate.latitude; 
    if (vu.coordinate.latitude > maxLat) maxLat = vu.coordinate.latitude; 
    if (vu.coordinate.longitude < minLon) minLon = vu.coordinate.longitude; 
    if (vu.coordinate.longitude > maxLon) maxLon = vu.coordinate.longitude; 
} 
CLLocation *newCenter = [[CLLocation alloc] initWithLatitude: (maxLat+minLat)/2.0 
                longitude: (maxLon+minLon)/2.0]; 
theMapView.region = MKCoordinateRegionMake (newCenter.coordinate, 
         MKCoordinateSpanMake(fabs(maxLat-minLat), fabs(maxLon-minLon)));