Create a polyline on iOs map with GPS coordinate

Question

In my app I count the footsteps and now I want to know the speed and I want to store the GPS coordinates to draw a polyline in another ViewController. I thought that I can store this coordinate by using the following code:

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

    if (currentLocation != nil) {
        locationArray = [[NSMutableArray alloc]init];
        [locationArray addObject:currentLocation];
        speed = (int) currentLocation.speed * 3.6;
        self.labelSpeed.text = [NSString stringWithFormat:@"%d Km/h",speed];
        NSLog(@"%@", [NSString stringWithFormat:@"%.8f", currentLocation.coordinate.longitude]);
        NSLog(@"%@", [NSString stringWithFormat:@"%.8f", currentLocation.coordinate.latitude]);
    }
}

But it doesn't works, because in my locationArray it stored only the last coordinates received by the GPS sensor. To explain you better what I'm trying to develop I will write here something much specific: In the first ViewController I want to show 2 label in which I calculate the number of steps and the speed. So in this ViewController I've to receive the coordinates data and I thought this data should be inserted in a NSMutableArray. In the second ViewController I show a label in which I will insert the total number of steps (by using a prepareForSegue method) and below a MapView in which I will draw a polyline to display the path I made. For that I need the coordinates that I received in the first ViewController, so I've to pass the data from the first to the second ViewController by using prepareForSegue method. My issue is how I can store all the coordinates to have them in the second ViewController to draw the polyline? Cna anyone help me?

Thank you

score 1 · Accepted Answer · answered Sep 04 '13 at 14:23

You are storing just the last coordinates because you are initializing your array every time you get a new location, move the allocation line to another method (like viewDidLoad) and erase that line in your didUpdateToLocation.

- (void)viewDidLoad
{
    [super viewDidLoad];
    locationArray = [[NSMutableArray alloc]init];
    //.... more code
}

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

    if (currentLocation != nil) {
        //locationArray = [[NSMutableArray alloc]init]; //This line doesn't go here
        [locationArray addObject:currentLocation];
        speed = (int) currentLocation.speed * 3.6;
        self.labelSpeed.text = [NSString stringWithFormat:@"%d Km/h",speed];
        NSLog(@"%@", [NSString stringWithFormat:@"%.8f", currentLocation.coordinate.longitude]);
        NSLog(@"%@", [NSString stringWithFormat:@"%.8f", currentLocation.coordinate.latitude]);
    }
}

Create a polyline on iOs map with GPS coordinate

1 Answers1