Turning user location annotation with heading

问题

I'm trying to change the User Annotation in my app so that it shows the usual blue dot, but with a triangle coming off of it to show which direction the user is facing (I'd rather rotate the user annotation than the entire map, which is what MKUserTrackingModeFollowWithHeading does). I've got a rudimentary version working, but it has some weird behavior.

First, some code:

-(MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id<MKAnnotation>)annotation {
     if ([annotation isKindOfClass:[MKUserLocation class]]) {
          _userLocationView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:@"userLocationIdentifier"];
          //use a custom image for the user annotation
          _userLocationView.image = [UIImage imageNamed:@"userLocationCompass.png"];

          return _userLocationView;

     } else {
          return nil;
     }

}

-(void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading {

     //rotate user location annotation based on heading from location manager.
     if (!_locatorButton.hidden) {
          CLLocationDirection direction = newHeading.magneticHeading;

          CGAffineTransform transform = CGAffineTransformMakeRotation(degreesToRadians(direction));
          _userLocationView.transform = transform;
     }

}

-(void)GPSButtonPressed:(id)sender {
    if (self.GPSEnabled) {
        //if GPS is already on, disable it.
        _mapview.showsUserLocation = NO;
        [_mapview removeAnnotation:_mapview.userLocation];
        self.GPSEnabled = NO;

        [_locationManager stopUpdatingHeading];

    } else {
        //enable GPS.
        _mapview.showsUserLocation = YES;
        self.GPSEnabled = YES;

        if ([CLLocationManager headingAvailable]) {
            [_locationManager startUpdatingHeading];
        }


    }
}

The user location annotation image shows up fine, and rotates based on the heading, but here are the funny behaviors:

1- The annotation does not follow my location-- it only stays in one place, but rotates with the correct heading. If I turn off the GPS with the "GPS Button", then turn it back on, the annotation shows up in the correct place, but still won't follow as I walk.

2- If I scroll the map, the annotation pops back to due north, then quickly rotates to the correct heading, causing an annoying flickering effect.

3- If I turn off the GPS and remove the user location, the annotation is removed as intended, but if I then scroll the map, the annotation pops back to the screen rather than staying hidden.

What am I doing wrong? Thanks for any helpful hints!

回答1:

Even if it is likely that you already fixed your 2. problem I still want to share the solution, which helped me with a similar problem.

I came across same problem: my custom user location arrow rotation was always popping back to north when the user scrolled or panned the map. I found the fix here: https://stackoverflow.com/a/12753320/2030629

according to the author it is a but in ios6 and can be fixed by adding

if(is6orMore) {
        [annView setTransform:CGAffineTransformMakeRotation(.001)]; //iOS6 BUG WORKAROUND !!!!!!!
 }

to mapView:viewForAnnotation.

I also set the transform in - mapView:regionDidChangeAnimated: again. Hope this will make someone else as happy as it made me :)

来源：https://stackoverflow.com/questions/14158812/turning-user-location-annotation-with-heading

标签

ios

mapkit

cllocationmanager

mkannotationview