IPhone - MKReverseGeocoder -如何确保我得到结果

Question

我想达到的是显示带有城市名称的注释。

所以我有一个类MapPoint：

@interface MapPoint : NSObject<MKAnnotation,MKReverseGeocoderDelegate> {

    NSString* title;
    NSString* cityName;
    CLLocationCoordinate2D coordinate;
    MKReverseGeocoder* reverseGeo;
}

@property (nonatomic,readonly) CLLocationCoordinate2D coordinate;
@property (nonatomic,copy) NSString* title;
@property (nonatomic,copy) NSString* cityName;

-(id) initWithCoordinate:(CLLocationCoordinate2D)c tilte:(NSString*)t;

@end

我是这样实现的：

@implementation MapPoint

@synthesize title,coordinate,cityName;

-(id) initWithCoordinate:(CLLocationCoordinate2D)c tilte:(NSString*)t
{
    [super init];
    coordinate = c;
    reverseGeo = [[MKReverseGeocoder alloc] initWithCoordinate:c];
    reverseGeo.delegate = self;
    [reverseGeo start];
    [self setTitle:t];
    return self;

}

- (void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFindPlacemark:(MKPlacemark *)placemark
{
    NSString* city = [placemark.addressDictionary objectForKey:(NSString*)kABPersonAddressCityKey];
    NSString* newString = [NSString stringWithFormat:@"city-> %@",city];
    [self setTitle:[title stringByAppendingString:newString]];
}

-(void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFailWithError:(NSError *)error{
    NSLog(@"error fetching the placemark");
}

-(void)dealloc
{
    [reverseGeo release];
    [cityName release];
    [title release];
    [super dealloc];
}

@end

然后，在我的CoreLocation委托中，我这样使用MapPoint：

-(void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
  MapPoint* mp = [[MapPoint alloc] initWithCoordinate:[newLocation coordinate] tilte:[locationTitleField text]];
    [mapView addAnnotation:mp];

    [mp release];

}

现在，我有两个我不确定的问题：

1. 是否正确地将reverseGeo作为数据成员，或者更好的选择是将其分配到初始化器中，并在didFindPlacemark/didFailWithError委托中释放它(甚至可以在那里发布它)？
2. 如何确保当我的注释显示时，我知道reverseGeo返回了一个答案(placemark或error -不管它是什么)。也许等待网络响应是错误的，我应该这样做--我只是不确定网络响应何时到达，它将相应地更新MapView中的MapView。

请尽量详细说明。谢谢

Answer 1

1. --把它作为数据成员存储是可以的。
2. 看起来像是在为用户的当前位置留下注释的线索？如果您正在用显示用户所在位置的“面包屑轨迹”来补充常规用户的当前位置注释，那么您需要等待将点添加到地图上，直到得到注释(如果这是您想要的行为)。我要么让管理您的映射的类成为MKReverseGeocoder委托(并让它设置标题属性，然后在reverseGeocoder:didFindPlacemark中将注释添加到映射中)，要么将映射引用添加到MapPoint类，并让它在同一个回调中将自己添加到映射中。

顺便说一下，MKReverseGeocoder的文档包括以下文本：

• When you want to update the location automatically (such as when the user is moving), reissue the reverse-geocoding request only when the user's location has moved a significant distance and after a reasonable amount of time has passed. For example, in a typical situation, you should not send more than one reverse-geocode request per minute.