如何在 Objective-C 中实现 MKClusterAnnotations？

Question

我正在尝试为我的 Apple 地图上彼此非常接近的注释创建集群视图。我知道 Apple 在 iOS 11 中推出了原生集群视图套件，但我在网上找到的所有教程都是用 Swift 编写的。我希望有人可以教我或推荐我任何我可以阅读的教程，以了解如何在 Objective-C 中实现集群注释。

我的想法是创建一个ClusterView类，它继承MKAnnotationView类，然后在mapView控制器中创建ClusterView的实例。

我已经阅读了苹果的文档，它只为您提供了我可能需要调用的函数，但没有解释如何使用它们，这是苹果文档的链接： https: //developer.apple.com/文档/mapkit/mkclusterannotation?language=objc

任何帮助，将不胜感激！

Answer 1

以下是基本步骤：

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1. 定义注释视图，指定clusteringIdentifier和collisionMode：

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   //  CustomAnnotationView.h\n\n@import MapKit;\n\n@interface CustomAnnotationView : MKMarkerAnnotationView\n\n@end\n

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   和

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   //  CustomAnnotationView.m\n\n#import "CustomAnnotationView.h"\n\nstatic NSString *identifier = @"com.domain.clusteringIdentifier";\n\n@implementation CustomAnnotationView\n\n- (instancetype)initWithAnnotation:(id<MKAnnotation>)annotation reuseIdentifier:(NSString *)reuseIdentifier {\n    if ((self = [super initWithAnnotation:annotation reuseIdentifier:reuseIdentifier])) {\n        self.clusteringIdentifier = identifier;\n        self.collisionMode = MKAnnotationViewCollisionModeCircle;\n    }\n\n    return self;\n}\n\n- (void)setAnnotation:(id<MKAnnotation>)annotation {\n    [super setAnnotation:annotation];\n\n    self.clusteringIdentifier = identifier;\n}\n\n@end\n

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2. 或者，如果需要，您可以定义自己的集群注释视图，指定displayPriority和collisionMode。这还更新了集群的图像以指示有多少注释被集群：

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   //  ClusterAnnotationView.h\n\n@import MapKit;\n\n@interface ClusterAnnotationView : MKAnnotationView\n\n@end\n

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   和

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   //  ClusterAnnotationView.m\n\n#import "ClusterAnnotationView.h"\n\n@implementation ClusterAnnotationView\n\n- (instancetype)initWithAnnotation:(id<MKAnnotation>)annotation reuseIdentifier:(NSString *)reuseIdentifier {\n    if ((self = [super initWithAnnotation:annotation reuseIdentifier:reuseIdentifier])) {\n        self.displayPriority = MKFeatureDisplayPriorityDefaultHigh;\n        self.collisionMode = MKAnnotationViewCollisionModeCircle;\n    }\n\n    return self;\n}\n\n- (void)setAnnotation:(id<MKAnnotation>)annotation {\n    super.annotation = annotation;\n    [self updateImage:annotation];\n}\n\n- (void)updateImage:(MKClusterAnnotation *)cluster {\n    if (!cluster) {\n        self.image = nil;\n        return;\n    }\n\n    CGRect rect = CGRectMake(0, 0, 40, 40);\n    UIGraphicsImageRenderer *renderer = [[UIGraphicsImageRenderer alloc] initWithSize:rect.size];\n    self.image = [renderer imageWithActions:^(UIGraphicsImageRendererContext * _Nonnull rendererContext) {\n        // circle\n\n        [[UIColor blueColor] setFill];\n        [[UIColor whiteColor] setStroke];\n\n        UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:rect];\n        path.lineWidth = 0.5;\n        [path fill];\n        [path stroke];\n\n        // count\n\n        NSString *text = [NSString stringWithFormat:@"%ld", (long) cluster.memberAnnotations.count];\n        NSDictionary<NSAttributedStringKey, id> *attributes = @{\n            NSFontAttributeName: [UIFont preferredFontForTextStyle: UIFontTextStyleBody],\n            NSForegroundColorAttributeName: [UIColor whiteColor]\n                                                                };\n        CGSize size = [text sizeWithAttributes:attributes];\n        CGRect textRect = CGRectMake(rect.origin.x + (rect.size.width  - size.width)  / 2,\n                                     rect.origin.y + (rect.size.height - size.height) / 2,\n                                     size.width,\n                                     size.height);\n        [text drawInRect:textRect withAttributes:attributes];\n    }];\n}\n\n@end\n

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   如果您不想，则不必为集群创建自己的子类。但这只是说明了如何完全控制集群的外观（如果您选择这样做）。

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3. 然后你的视图控制器只需要注册适当的类，你\xe2\x80\x99就完成了（不需要地图视图委托）：

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   [self.mapView registerClass:[CustomAnnotationView class] forAnnotationViewWithReuseIdentifier:MKMapViewDefaultAnnotationViewReuseIdentifier];\n

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   如果您想使用自定义集群视图，您也可以注册它：

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   [self.mapView registerClass:[ClusterAnnotationView class] forAnnotationViewWithReuseIdentifier:MKMapViewDefaultClusterAnnotationViewReuseIdentifier];\n

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   例如：

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   //  ViewController.m\n\n#import \xe2\x80\x9cViewController.h"\n\n@import MapKit;\n\n#import "CustomAnnotationView.h"\n#import "ClusterAnnotationView.h"\n\n@interface ViewController ()\n@property (weak, nonatomic) IBOutlet MKMapView *mapView;\n@end\n\n@implementation ViewController\n\n- (void)viewDidLoad {\n    [super viewDidLoad];\n\n    [self configureMapView];\n}\n\n- (void)configureMapView {\n    self.mapView.userTrackingMode = MKUserTrackingModeFollow;\n\n    [self.mapView registerClass:[CustomAnnotationView class] forAnnotationViewWithReuseIdentifier:MKMapViewDefaultAnnotationViewReuseIdentifier];\n    [self.mapView registerClass:[ClusterAnnotationView class] forAnnotationViewWithReuseIdentifier:MKMapViewDefaultClusterAnnotationViewReuseIdentifier];\n}\n\n// I\xe2\x80\x99m going to search for restaurants and add annotations for those,\n// but do whatever you want\n\n- (void)performSearch {\n    MKLocalSearchRequest *request = [[MKLocalSearchRequest alloc] init];\n    request.naturalLanguageQuery = @"restaurant";\n    request.region = self.mapView.region;\n\n    MKLocalSearch *search = [[MKLocalSearch alloc] initWithRequest:request];\n    [search startWithCompletionHandler:^(MKLocalSearchResponse * _Nullable response, NSError * _Nullable error) {\n        if (error) {\n            NSLog(@"%@", error);\n            return;\n        }\n\n        for (MKMapItem *mapItem in response.mapItems) {\n            MKPointAnnotation *annotation = [[MKPointAnnotation alloc] init];\n            annotation.coordinate = mapItem.placemark.coordinate;\n            annotation.title = mapItem.name;\n            annotation.subtitle = mapItem.placemark.thoroughfare;\n            [self.mapView addAnnotation:annotation];\n        }\n    }];\n}\n\n@end\n

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得出：

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