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我正在尝试plotParkingLots从我的 AppDelegate 调用，因为我希望在应用程序启动时首先调用它（然后每隔 x 秒我将在稍后实现）。

plotParkingLots如果我通过我的 MapViewControllerviewDidLoad调用它可以正常工作，但是当我从 AppDelegate 调用它时，它不起作用。

我知道它被调用了，但是当我切换到我的地图视图时，没有显示注释！

MapViewController.h

#import <UIKit/UIKit.h>
#import <MapKit/MapKit.h>

#define METERS_PER_MILE 1609.344

@interface MapViewController : UIViewController <MKMapViewDelegate>

@property (strong, nonatomic) IBOutlet MKMapView *mapView;

- (void)plotParkingLots;

@end

MapViewController.m

- (void)plotParkingLots {
    NSString *url = [NSString stringWithFormat:@"http:/localhost/testes/parking.json"];
    NSData *jsonData = [NSData dataWithContentsOfURL: [NSURL URLWithString:url]];

    if (jsonData == nil) {
        UIAlertView *alertBox = [[UIAlertView alloc] initWithTitle: @"Erro de conexão" message: @"Não foi possível retornar os dados dos estacionamentos" delegate: self cancelButtonTitle: @"Ok" otherButtonTitles: nil];
        [alertBox show];
    }
    else {
        NSError *error;
        NSDictionary *json = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&error];

        NSArray *parkings = [json objectForKey:@"parkings"];
        for (NSDictionary * p in parkings) {
            Parking *annotation = [[Parking alloc] initWithDictionary:p];
            [_mapView addAnnotation:annotation];
        }
    }
 }

- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation {

    static NSString *identifier = @"Parking";
    if ([annotation isKindOfClass:[Parking class]]) {
        MKPinAnnotationView *annotationView = (MKPinAnnotationView *) [_mapView dequeueReusableAnnotationViewWithIdentifier:identifier];
        if (annotationView == nil) {
            annotationView = [[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:identifier];
        } else {
            annotationView.annotation = annotation;
        }

        annotationView.enabled = YES;
        annotationView.canShowCallout = YES;
        annotationView.image=[UIImage imageNamed:@"car.png"];

        return annotationView;
    }

    return nil;    
}

AppDelegate.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Override point for customization after application launch.
    [[MapViewController alloc] plotParkingLots];

    return YES;
}
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1 回答 1

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您不是在与向用户显示的 MapViewController 交谈。在您的 AppDelegate 中，您暂时分配了一个 MapViewController，绘制停车场，然后放弃该 MapViewController 并且不再使用它。

You'll need to keep a handle to that controller so that when the user presses something to make that viewcontroller get displayed it is the same one that has just plotted the parking lots.

于 2012-09-27T20:57:03.390 回答