在MKMapView上重新加载时切换的自定义注释

Question

我已经有这个问题好几个星期了，但我仍然没有找到答案。在我的MapView上，我有自定义注释，当我点击"重新加载按钮"时，所有信息都是正确的，就像注释"标题，副标题"中一样。但是注释已经改变了。注释在NSMutableArray中，我确信我的问题围绕着这个。这是我用来重新加载注释的代码。

因此，为了防止混淆，当我第一次加载mapView时，我的自定义注释工作得很好。但一旦我点击重载按钮，所有注释的信息，如"位置、标题、副标题"，都是正确的，只是实际的注释发生了变化。就像所有的注释都被切换了一样。如果有人能帮忙，我们将不胜感激！谢谢

- (IBAction)refreshMap:(id)sender {
NSArray *annotationsOnMap = myMapView.annotations;
[myMapView removeAnnotations:annotationsOnMap];
[locations removeAllObjects];
[citiesArray removeAllObjects];
[self retrieveData];
}

-(void) retrieveData {
userLAT = [NSString stringWithFormat:@"%f", myMapView.userLocation.coordinate.latitude];
userLNG = [NSString stringWithFormat:@"%f", myMapView.userLocation.coordinate.longitude];
NSString *fullPath = [mainUrl stringByAppendingFormat:@"map_json.php?userID=%@&lat=%@&lng=%@",theUserID,userLAT,userLNG];
NSURL * url =[NSURL URLWithString:fullPath];
NSData *data = [NSData dataWithContentsOfURL:url];
json =[NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil];

citiesArray =[[NSMutableArray alloc]init];
for (int i = 0; i < json.count; i++)
{
    //create city object
    NSString * eID =[[json objectAtIndex:i] objectForKey:@"userid"];
    NSString * eAddress =[[json objectAtIndex:i] objectForKey:@"full_address"];
    NSString * eHost =[[json objectAtIndex:i] objectForKey:@"username"];
    NSString * eLat =[[json objectAtIndex:i] objectForKey:@"lat"];
    NSString * eLong =[[json objectAtIndex:i] objectForKey:@"lng"];
    NSString * eName =[[json objectAtIndex:i] objectForKey:@"Restaurant_name"];
    NSString * eState = [[json objectAtIndex:i] objectForKey:@"type"];
    NSString * annotationPic = [[json objectAtIndex:i] objectForKey:@"Annotation"];
    NSString * eventID = [[json objectAtIndex:i] objectForKey:@"id"];
    //convert lat and long from strings
    float floatLat = [eLat floatValue];
    float floatLONG = [eLong floatValue];
    City * myCity =[[City alloc] initWithRestaurantID: (NSString *) eID andRestaurantName: (NSString *) eName andRestaurantState: (NSString *) eState andRestaurantAddress: (NSString *) eAddress andRestaurantHost: eHost andRestaurantLat: (NSString *) eLat andRestaurantLong: (NSString *) eLong];
    //Add our city object to our cities array
    // Do any additional setup after loading the view.
    [citiesArray addObject:myCity];
    //Annotation
    locations =[[NSMutableArray alloc]init];
    CLLocationCoordinate2D location;
    Annotation * myAnn;
    //event1 annotation
    myAnn =[[Annotation alloc]init];
    location.latitude = floatLat;
    location.longitude = floatLONG;
    myAnn.coordinate = location;
    myAnn.title = eName;
    myAnn.subtitle = eHost;
    myAnn.type = eState;
    myAnn.AnnotationPicture = annotationPic;
    myAnn.passEventID = eventID;
    myAnn.hotZoneLevel = hotZone;
    [locations addObject:myAnn];
    [self.myMapView addAnnotations:locations];
}
}

 - (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation
{
if([annotation isKindOfClass:[MKUserLocation class]])
    return nil;
static NSString *annotationIdentifier = @"AnnotationIdentifier";
MKAnnotationView *annotationView = (MKAnnotationView *) [self.myMapView
                                                         dequeueReusableAnnotationViewWithIdentifier:annotationIdentifier];
if (!annotationView)
{
    annotationView = [[MKAnnotationView alloc]
                      initWithAnnotation:annotation
                      reuseIdentifier:annotationIdentifier];
    NSString *restaurant_Icon = ((Annotation *)annotation).AnnotationPicture;
    NSString *restaurant_Callout = [NSString stringWithFormat:@"mini.%@",restaurant_Icon];
    UIImage *oldImage = [UIImage imageNamed:restaurant_Icon];
    UIImage *newImage;
    CGSize newSize = CGSizeMake(75, 75);
    newImage = [oldImage imageScaledToFitSize:newSize]; // uses MGImageResizeScale

    annotationView.image= newImage;
    annotationView.canShowCallout = YES;
    UIImage *Mini_oldImage = [UIImage imageNamed:event_Callout];
    UIImage *Mini_newImage;
    CGSize Mini_newSize = CGSizeMake(30,30);
    Mini_newImage = [Mini_oldImage imageScaledToFitSize:Mini_newSize]; // uses MGImageResizeScale
    UIImageView *finalMini_callOut = [[UIImageView alloc] initWithImage:Mini_newImage];
    annotationView.leftCalloutAccessoryView = finalMini_callOut;

    UIButton* rightButton = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];

    annotationView.rightCalloutAccessoryView = rightButton;
}
else
{
    annotationView.annotation = annotation;
}
return annotationView;
}

Answer 1

如果没有其他内容，则根据注释设置图标和标注，但仅在注释未出列的情况下在viewForAnnotation中进行设置。您确实希望在if块之外执行任何特定于注释的自定义，以防重用注释视图。

---

与您报告的问题无关，还有一些其他观察结果：

1. 您可能应该异步执行retrieveData，这样就不会将主线程与数据检索/解析联系在一起。继续执行将条目添加到数组的调度，并将注释添加到主队列中的映射，但网络方面的工作肯定应该异步完成。

2. 您可能应该检查以确保data不是nil（例如，没有网络连接或其他网络错误），因为如果您传递nil值，JSONObjectWithData将崩溃。

3. 您似乎没有必要使用locations，因为您要为JSON中的每个条目重置它。您可以（a）完全撤销locations，只需将myAnn对象添加到地图的注释中；或者（b）在CCD_ 12循环之前初始化CCD_。但是，维护这个ivar，但只使用最后一个注释填充它，可能会产生误导。