iphone - 未调用 removeAnnotation 方法

Question

注释方法 removeAnnotation 没有被调用，所以 map 上的图像在更新位置时会被复制。如何调用 removeAnnotation 方法以便我们可以从旧位置删除图像。

<pre>
- (MKAnnotationView *)mapView:(MKMapView *)map viewForAnnotation:(id <MKAnnotation>)annotation
{
    static NSString *AnnotationViewID = @"annotationViewID";

    MKAnnotationView *annotationView = (MKAnnotationView *)[map dequeueReusableAnnotationViewWithIdentifier:AnnotationViewID];

    if (annotationView == nil)
    {
        annotationView = [[[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:AnnotationViewID] autorelease];
    }

    annotationView.image = [UIImage imageNamed:@"Bike.png"];
    annotationView.annotation = annotation;

    return annotationView;
}

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
    // here do
    //UIImage *pinImage = [UIImage imageNamed:@"Bike.png"];
    CLLocation *currentLocation = newLocation;
    if(currentLocation != nil)
    {
        CLLocationCoordinate2D location = CLLocationCoordinate2DMake(currentLocation.coordinate.latitude, currentLocation.coordinate.longitude);
        MyAnnotation *annotation = [[MyAnnotation alloc] initWithCoordinates:location title:@"India" subTitle:@"Sarvopari Mall"];
        if (newLocation)
        {
            [self.myMapView removeAnnotation:annotation];
        }
        [self.myMapView addAnnotation:annotation];
    }
}
</pre>

Answer 1

在将注释添加到 map 时，您应该将注释保留为实例变量或属性。然后在位置更新时，删除以前的注释(存储在实例变量中)并添加新的。

您应该像这样修改您的 UIViewController:

@interface YourViewController : UIViewController
{
    MyAnnotation *annotation;
}

@end

然后像这样修改您的 LocationManager Delegate 方法:

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation{
    // here do
    //UIImage *pinImage = [UIImage imageNamed:@"Bike.png"];
    CLLocation *currentLocation = newLocation;
    if(currentLocation != nil)
    {
        //Removes previous annotation
        if(annotation){
            [self.myMapView removeAnnonation:annotation];
        }
        CLLocationCoordinate2D location = CLLocationCoordinate2DMake(currentLocation.coordinate.latitude, currentLocation.coordinate.longitude);
        //Keeps annotation in an instance variable
        annotation = [[MyAnnotation alloc] initWithCoordinates:location title:@"India" subTitle:@"Sarvopari Mall"];
        [self.myMapView addAnnotation:annotation];
    }
}