iphone - MKMapView で正しいズームを設定する

Question

歩数カウント アプリを作成しました。iPhone の加速度計で歩数をカウントしました。作成したパスを mapView に表示したいと思います。地図を簡単に表示し、iPhone GPS で正しい位置をキャッチできます。始点と終点を表示し、作成したパスを示すポリラインを描画できます。今私の問題は、マップ上で正しいズームを設定する方法ですか? ズームをマップしてViewControllerを開くと、遠すぎて、作成したパスを表示するためにズームする必要があります。だから私の質問は、正しいズームを設定する方法ですか?

ここに、mapView を使用した View Controller のコードを投稿します。

ResultViewController.m

#import "ResultViewController.h"
#import "MapAnnotation.h"

@interface ResultViewController ()
@property (nonatomic, strong)NSMutableArray *mapAnnotation;
@property (nonatomic) BOOL needUpdateRegion;
@end

@implementation ResultViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.labelResult.text = self.totalSteps;
    [self.mapView setDelegate:self];
    self.needUpdateRegion = YES;
    self.mapAnnotation = [[NSMutableArray alloc]initWithCapacity:2];
    CLLocation *startLocation = [self.locationArray objectAtIndex:0];
    CLLocation *stopLocation = [self.locationArray lastObject];
    NSString *startLatitude = [NSString stringWithFormat:@"%f", startLocation.coordinate.latitude];
    NSString *startLongitude = [NSString stringWithFormat:@"%f", startLocation.coordinate.longitude];
    NSString *stopLatitude = [NSString stringWithFormat:@"%f", stopLocation.coordinate.latitude];
    NSString *stopLongitude = [NSString stringWithFormat:@"%f", stopLocation.coordinate.longitude];

    MapAnnotation *startPlace = [[MapAnnotation alloc]initWithCoordinate:startLatitude andLong:startLongitude];
    MapAnnotation *stopPlace = [[MapAnnotation alloc]initWithCoordinate:stopLatitude andLong:stopLongitude];

    [self.mapAnnotation insertObject:startPlace atIndex:0];
    [self.mapAnnotation insertObject:stopPlace atIndex:1];

    if (self.mapAnnotation) {
        [self.mapView removeAnnotations:self.mapView.annotations];
    }

    [self.mapView addAnnotation:self.mapAnnotation[0]];
    [self.mapView addAnnotation:self.mapAnnotation[1]];
    [self updateRegion];
    [self createMKpolylineAnnotation];
}

- (void)updateRegion
{
    self.needUpdateRegion = NO;
    CGRect boundingRect;
    BOOL started = NO;
    for (id <MKAnnotation> annotation in self.mapView.annotations) {
        CGRect annotationRect = CGRectMake(annotation.coordinate.latitude, annotation.coordinate.longitude, 0, 0);
        if (!started) {
            started = YES;
            boundingRect = annotationRect;
        } else {
            boundingRect = CGRectUnion(boundingRect, annotationRect);
        }
    }
    if (started) {
        boundingRect = CGRectInset(boundingRect, -0.2, -0.2);
        if ((boundingRect.size.width < 20) && (boundingRect.size.height < 20)) {
            MKCoordinateRegion region;
            region.center.latitude = boundingRect.origin.x + boundingRect.size.width / 2;
            region.center.longitude = boundingRect.origin.y + boundingRect.size.height / 2;
            region.span.latitudeDelta = boundingRect.size.width;
            region.span.longitudeDelta = boundingRect.size.height;
            [self.mapView setRegion:region animated:YES];
        }
    }
}

- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay {
    MKPolylineView *polylineView = [[MKPolylineView alloc] initWithPolyline:overlay];
    polylineView.strokeColor = [UIColor blueColor];
    polylineView.lineWidth = 5.0;

    return polylineView;
}


- (void)createMKpolylineAnnotation {
    NSInteger numberOfSteps = self.locationArray.count;

    CLLocationCoordinate2D *coords = malloc(sizeof(CLLocationCoordinate2D) * numberOfSteps);
    for (NSInteger index = 0; index < numberOfSteps; index++) {
        CLLocation *location = [self.locationArray objectAtIndex:index];
        CLLocationCoordinate2D coordinate = location.coordinate;
        coords[index] = coordinate;
    }

    MKPolyline *polyLine = [MKPolyline polylineWithCoordinates:coords count:numberOfSteps];
    [self.mapView addOverlay:polyLine];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)restart:(id)sender {
    [self dismissViewControllerAnimated:YES completion:nil];
}
@end

このコードの何が問題になっていますか? 地図を正しくズームするのを手伝ってくれる人はいますか?

ありがとうございました