ios - MapView Pin 注释的问题 - 本地图缩放/平移/区域更改时 Pin 会失去颜色

Question

我有一个显示现金点位置的 map View 。注释将被删除，并且可以单击标注以转到包含有关该位置的更多详细信息的页面。提款机分为免费和付费两类，免费提款机的针脚为绿色，另一种为红色。当别针掉落时，它们的颜色是正确的。一切正常，直到我缩放到用户位置或 map 的其他区域，然后当我返回到图钉时，它们已经丢失了颜色格式并且全部是原始的红色。

我认为这与下载图 block 时 map 重新加载有关，并且没有正确重新加载引脚，尽管我可能是错的。

任何帮助将不胜感激。

这是我的代码:

#import "CashPointMapViewController.h"
#import "PinDrop.h"
#import "CashPointDetailViewController.h"

@implementation CashPointMapViewController
@synthesize app, theCashList, mapview, ann, count, myArray, pinColor;

- (IBAction) getlocation { 

    MKCoordinateRegion region;
    region.center = self.mapview.userLocation.coordinate;
    region.span.longitudeDelta = 0.01f;
    region.span.longitudeDelta = 0.01f;
    [mapview setRegion:region animated:YES];
}

- (void)viewDidLoad {

    [super viewDidLoad];

    mapview.showsUserLocation = YES;

    [mapview setMapType:MKMapTypeStandard];
    [mapview setZoomEnabled:YES];
    [mapview setScrollEnabled:YES];

    MKCoordinateRegion region = { {0.0, 0.0 }, {0.0, 0.0 } };
    region.center.latitude = 53.801279;
    region.center.longitude = -1.548567;
    region.span.longitudeDelta = 0.3f;
    region.span.longitudeDelta = 0.3f;
    [mapview setRegion:region animated:YES];

    app = [[UIApplication sharedApplication]delegate];

    UIImage *locate = [UIImage imageNamed:@"location arrow white.png"];

    UIBarButtonItem *userlocatebutton = [[UIBarButtonItem alloc] initWithImage:locate     style:UIBarButtonItemStylePlain target:self action:@selector(getlocation)];

    self.navigationItem.rightBarButtonItem = userlocatebutton;

    [self performSelectorInBackground:@selector(annloop) withObject:self];

}


-(void) annloop {

    int i;
    for (i=0; i<=count-1; i = i+1) {
    theCashList = [myArray objectAtIndex:i];

    NSString *trimlat = [theCashList.lat stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
    NSString *trimlon = [theCashList.lon stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

    double latdouble = [trimlat doubleValue];
    double londouble = [trimlon doubleValue];

    CLLocationCoordinate2D coord = {(latdouble),(londouble)};

    ann = [[PinDrop alloc] init];

    ann.index = i;

    ann.title = [theCashList.name stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

    NSString *street = [theCashList.street stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
    NSString *town = [theCashList.town stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
    NSString *postcode = [theCashList.postcode stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

    NSString *address = [[NSString alloc] initWithFormat:@"%@, %@, %@", street, town, postcode];

    ann.subtitle = address;
    ann.coordinate = coord;

    NSString *trimprice = [theCashList.price stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

    if ([trimprice isEqualToString:@"Free"])
    {
        ann.price = 1;
    }
    else
    {
        ann.price = 0;
    }
    [mapview performSelectorOnMainThread:@selector(addAnnotation:) withObject:ann waitUntilDone:YES];
    }
}


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

    if ([annotation isKindOfClass:[MKUserLocation class]])
    return nil;

    MKPinAnnotationView *mypin = [[MKPinAnnotationView alloc]initWithAnnotation:ann reuseIdentifier:@"current"];
    mypin.backgroundColor = [UIColor clearColor];
    UIButton *goToDetail = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
    mypin.rightCalloutAccessoryView = goToDetail;
    mypin.draggable = NO;
    mypin.animatesDrop = TRUE;
    mypin.canShowCallout = YES;


    if (ann.price == 1)
    {
        mypin.pinColor = MKPinAnnotationColorGreen;
    }
    else
    {
        mypin.pinColor = MKPinAnnotationColorRed;
    }
    return mypin;
    }


- (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view
calloutAccessoryControlTapped:(UIControl *)control {

   PinDrop *annView = view.annotation;
    CashPointDetailViewController *detailView = [[CashPointDetailViewController alloc]init];
    theCashList = [myArray objectAtIndex:annView.index];
    detailView.theCashList = theCashList;
    [self.navigationController pushViewController:detailView animated:YES];

}


- (void)viewDidUnload {

    [super viewDidUnload];
}

- (BOOL)shouldAutorotateToInterfaceOrientation:   (UIInterfaceOrientation)interfaceOrientation {
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

@end

编辑:这是我的 .h 如果有帮助的话。

#import <UIKit/UIKit.h>
#import "AppDelegate.h"
#import "CashPointList.h"
#import <MapKit/MapKit.h>
#import "PinDrop.h"

@interface CashPointMapViewController : UIViewController  {

    MKMapView *mapview;
    PinDrop *ann;
}

    @property (nonatomic, retain) AppDelegate *app;
    @property (nonatomic, retain) CashPointList *theCashList;
    @property (nonatomic, retain) PinDrop *ann;
    @property (nonatomic, retain) IBOutlet MKMapView *mapview;
    @property (nonatomic, readwrite) int count;
    @property (nonatomic, retain) NSMutableArray *myArray;
    @property (nonatomic) MKPinAnnotationColor pinColor;

    -(IBAction) getlocation;


@end

Answer 1

这不是与 map 重新加载图 block 相关的问题。

问题在于 viewForAnnotation 委托(delegate)中的代码使用 ann 对象，并错误地假设类实例级别 ann > 每当调用委托(delegate)方法时，对象都会同步。

viewForAnnotation 委托(delegate)不一定按照您添加注释的顺序调用，并且如果 map 需要重新显示某个注释，则可以针对同一注释调用多次次当它返回 View 时注释。

当为先前添加的注释再次调用委托(delegate)方法时，ann 和 annotation 不再指向同一对象。 ann 现在可能指向最后添加的注释，因此所有注释都会更改为其颜色。

在该委托(delegate)方法中，您必须使用annotation参数，该参数是对 map View 想要当前调用中的 View 的注释的引用(这可能是与您的外部循环完全无关)。

所以这一行:

MKPinAnnotationView *mypin = [[MKPinAnnotationView alloc] 
    initWithAnnotation:ann reuseIdentifier:@"current"];

应该是:

MKPinAnnotationView *mypin = [[MKPinAnnotationView alloc] 
    initWithAnnotation:annotation reuseIdentifier:@"current"];
                       ^^^^^^^^^^

并且在检查注释的属性时，使用annotation参数(并将其转换为您的自定义类以获取自定义属性):

PinDrop *ann = (PinDrop *)annotation;
//Note that this local "ann" is NOT the same as the class-level "ann".
//May want to use a different name to avoid confusion.
//The compiler may also warn you about this.

if (ann.price == 1)
...

一个单独的、不相关的但强烈推荐的建议是通过使用 dequeueReusableAnnotationViewWithIdentifier 来实现注释 View 的重用。当您有大量注释时，这将提高性能。