如何使用MapKit关注用户位置

Question

I'm using MapKit to display the user's location relative to pins around them. I'd like to be able to mimic the functionality that Maps provides via the crosshair button in the lower left-hand corner of the screen. I'm already aware that MapKit provides a CLLocation object with the user's location via MKUserLocation, I just wanted to seek advice on how I should keep focus on that location. My initial inclination was to use an NSTimer to center the map on that coordinate every 500ms or so.

Is there a better way to do this? Is there something built in to MapKit that I'm missing that will accomplish this?

Thanks so much, Brendan

Answer 1

If you're on IOS5+ this is VERY easy. Just change the "userTrackingMode" using code such as:

[_mapView setUserTrackingMode:MKUserTrackingModeFollow animated:YES];

This will smoothly follow the users current location. If you drag the map it will even set the tracking mode back to MKUserTrackingModeNone which is usually the behaviour you want.

Answer 2

It's really simple to have the map update the user location automatically just like the google maps. Simply set showsUserLocation to YES

self.mapView.showsUserLocation = YES

...and then implement the MKMapViewDelegate to re-center the map when the location is updated.

-(void)               mapView:(MKMapView *)mapView 
        didUpdateUserLocation:(MKUserLocation *)userLocation
{
    if( isTracking )
    {
        pendingRegionChange = YES;
        [self.mapView setCenterCoordinate: userLocation.location.coordinate
                                 animated: YES];
    }
}

And to allow the user to zoom & pan without stealing the view back to the current location...

-(void) mapView:(MKMapView *)mapView regionWillChangeAnimated:(BOOL)animated
{
    if( isTracking && ! pendingRegionChange )
    {
         isTracking = NO;
         [trackingButton setImage: [UIImage imageNamed: @"Location.png"] 
                         forState: UIControlStateNormal];
    }

    pendingRegionChange = NO;
}

-(IBAction) trackingPressed
{
    pendingRegionChange = YES;
    isTracking = YES;
    [mapView setCenterCoordinate: mapView.userLocation.coordinate 
                        animated: YES];

    [trackingButton setImage: [UIImage imageNamed: @"Location-Tracking.png"] 
                    forState: UIControlStateNormal];
}

Answer 3

I think that I would actually use the CoreLocation CLLocationManager and use its delegate method locationManager:didUpdateToLocation:fromLocation: .

This way, you don't have the overhead of an NSTimer , and it only updates when there's a new location available.

You can pull the longitude and latitude from the CLLocation object sent to the locationManager:didUpdateToLocation:fromLocation: method and pass it to the map view.

Answer 4

I go with Jacob Relkin's answer. This tutorial provides a step-by-step procedure of using CoreLocation in an iPhone app. Hope this helps you.

All the Best.