过滤 MKMapView

Posted 2023-03-05

【中文标题】过滤 MKMapView

【英文标题】：Filtering MKMapView

【发布时间】：2016-05-23 17:57:41

【问题描述】：

我有一个 MKMapView，它显示 JSON 文件中的一些注释并显示用户当前位置5 英里..

基本上就像foursquare上的地图过滤，您可以过滤您希望餐厅显示距离您的位置多远

这是我与问题相关的主要当前代码..

@interface ViewController () <MKMapViewDelegate , CLLocationManagerDelegate>

@property (weak, nonatomic) IBOutlet MKMapView *mapView;
@property (weak, nonatomic) CLLocationManager *locationManager;

@end

@implementation ViewController

@synthesize mapView;

/*
 Establish MapView delegate
 Add the Gesture Recogniser to the Map
 */
- (void)viewDidLoad

    [super viewDidLoad];
    [self.mapView setDelegate:self];
    //[self addGestureRecogniserToMapView];

    mapView.showsUserLocation= YES;
    mapView.showsTraffic = YES;
    mapView.showsBuildings = YES;

  __block NSArray *annoations;

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^

    annoations = [self parseJSONCities];

    dispatch_async(dispatch_get_main_queue(), ^(void) 

        [self.mapView addAnnotations:annoations];
        [self.mapView showAnnotations:annoations animated:YES];

    );
);

    if ([CLLocationManager locationServicesEnabled]) 
        self.locationManager.delegate = self;
        self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;
        [self.locationManager startUpdatingLocation];
        [self.locationManager requestWhenInUseAuthorization];
        NSLog(@"Location :)");
     else 
        NSLog(@"-)_");
    


   


- (NSMutableArray *)parseJSONCities

    NSMutableArray *retval = [[NSMutableArray alloc]init];
    NSString *jsonPath = [[NSBundle mainBundle] pathForResource:@"capitals"
                                                         ofType:@"json"];
    NSData *data = [NSData dataWithContentsOfFile:jsonPath];
    NSError *error = nil;
    NSArray *json = [NSJSONSerialization JSONObjectWithData:data
                                                    options:kNilOptions
                                                      error:&error];

    for (JFMapAnnotation *record in json) 

        JFMapAnnotation *temp = [[JFMapAnnotation alloc]init];
        [temp setTitle:[record valueForKey:@"Capital"]];
        [temp setSubtitle:[record valueForKey:@"Country"]];
        [temp setCoordinate:CLLocationCoordinate2DMake([[record valueForKey:@"Latitude"]floatValue], [[record valueForKey:@"Longitude"]floatValue])];
        [retval addObject:temp];

    

    return retval;

【参考方案1】：

使用记录的坐标，用初始化器创建一个CLLocation对象

init(latitude latitude: CLLocationDegrees, longitude longitude: CLLocationDegrees)

从那里，使用实例方法

distanceFromLocation(_:CLLocation)

使用用户位置获取注释与用户之间的距离（以米为单位）。之后，从米到英里的简单转换（除以 1609.34） 应该可以很好地过滤掉哪些注释是可见的。祝你好运！

【讨论】：

@Aryan，我很想知道这个解决方案是如何为你工作的。您需要进一步的帮助吗？请回复。