当用户步行或沿着道路行驶时，路线不会构建

Question

嗨，我是IOS的初学者，在我的项目中，我试图在用户步行或沿着公路行驶时构建路线

我正在尝试从GPS获取经度和纬度值，但是根不是构造，这意味着多线不在坐标之间构建，当我运行应用程序异常即将到来时请帮助我一些（如果有错误的话）请发布工作代码而不是它）

我的代码如下： -

#import "ViewController.h"
#import "MyAnnotation.h"
#define spanone 0.01f;

@interface ViewController ()
{
    NSMutableArray* MainAnnotations;
    NSString * latitude;
    NSString * longtude;

}

@property (nonatomic, strong) MKPolylineView *lineView;
@property (nonatomic, strong) MKPolyline *polyline;

@end

@implementation ViewController

@synthesize mapobj;

- (void)viewDidLoad {

    [super viewDidLoad];

    locmanager = [[CLLocationManager alloc] init];
    [locmanager setDelegate:self];

    if ([locmanager respondsToSelector:@selector(requestAlwaysAuthorization)])
    {
        [locmanager requestAlwaysAuthorization];
    }

    [locmanager setDistanceFilter:100.0f];
    [locmanager setDesiredAccuracy:kCLLocationAccuracyNearestTenMeters];

    [locmanager startUpdatingLocation];

}

- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
    NSLog(@"didFailWithError: %@", error);
    UIAlertView *errorAlert = [[UIAlertView alloc]
                               initWithTitle:@"Error" message:@"Failed to Get Your Location" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [errorAlert show];
}

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
    NSLog(@"didUpdateToLocation: %@", newLocation);
    CLLocation *currentLocation = newLocation;

    if (currentLocation != nil) {

        latitude = [NSString stringWithFormat:@"%.8f", currentLocation.coordinate.longitude];
        longtude = [NSString stringWithFormat:@"%.8f", currentLocation.coordinate.latitude];

        NSLog(@"latitude value %@",latitude);
        NSLog(@"longtude value %@",longtude);
    }

    [self createAnnotations];
}

- (void)createAnnotations
{
    //Region
    MKCoordinateRegion myRegion;

    //Center
    CLLocationCoordinate2D center;
    center.latitude = [latitude doubleValue];
    center.longitude = [longtude doubleValue];

    //span
    MKCoordinateSpan span;
    span.latitudeDelta = spanone
    span.longitudeDelta = spanone;

    //Myregion
    myRegion.center = center;
    myRegion.span = span;
    [mapobj setRegion:myRegion animated:YES];

    //create annotations
    CLLocationCoordinate2D myannotations;
    myannotations.latitude = [latitude doubleValue];
    myannotations.longitude = [longtude doubleValue];

    MainAnnotations = [[NSMutableArray alloc]init];

    CLLocationCoordinate2D new_coordinate = CLLocationCoordinate2DMake(myannotations.latitude, myannotations.longitude);
    [MainAnnotations addObject:[NSValue valueWithMKCoordinate:new_coordinate]];

    NSLog(@"array list %lu",(unsigned long)MainAnnotations.count);

    MyAnnotation * annotation = [[MyAnnotation alloc]init];
    annotation.coordinate = myannotations;
    annotation.title = @"Hi";
    annotation.subtitle = @"how are you";

    [mapobj addAnnotations:[NSArray arrayWithObjects:annotation,nil]];

    CLLocationCoordinate2D coordinate = [[MainAnnotations objectAtIndex:0] MKCoordinateValue];

    NSLog(@"array values %lu",coordinate);

    NSLog(@"main values is %d",mainValue);

    [self drawPolyline];
}

-(void)drawPolyline
{
    [mapobj removeOverlay:self.polyline];

    // create an array of coordinates from allPins
    CLLocationCoordinate2D coordinates[MainAnnotations.count];
    int i = 0;
    for (MyAnnotation *currentLoc in MainAnnotations) {
        coordinates[i] = currentLoc.coordinate;
        i++;
    }

    // create a polyline with all cooridnates
    MKPolyline *polyline = [MKPolyline polylineWithCoordinates:coordinates count:MainAnnotations.count];
    [mapobj addOverlay:polyline];
    self.polyline = polyline;

}

- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay
{
    MKOverlayView* overlayView = nil;

    if(overlay == self.polyline)
    {
        //if we have not yet created an overlay view for this overlay, create it now.
        if (self.lineView) {
            [self.lineView removeFromSuperview];
        }

        self.lineView = [[MKPolylineView alloc] initWithPolyline:self.polyline];
        self.lineView.fillColor = [UIColor redColor];
        self.lineView.strokeColor = [UIColor greenColor];
        self.lineView.lineWidth = 10;

        overlayView = self.lineView;
    }

    return overlayView;
}


@end