注释针脚

Question

所以，我在MKMapView上为注释引脚设置位置时遇到了问题。

我只是从NSObject编写一个可遗传的类，名为“Annotation”，它使用协议。

所以，这是代码：

Annotation.h

#import <Foundation/Foundation.h>

@interface Annotation : NSObject <MKAnnotation>
{
    CLLocationCoordinate2D _coordinate;
    NSUInteger _pinID;
}

@property (nonatomic, readonly) CLLocationCoordinate2D coordinate;

- (id)initWithCoordinate:(CLLocationCoordinate2D)coordinate andID:(NSUInteger)pinID;

@end

Annotation.m

#import "Annotation.h"

@implementation Annotation

@synthesize coordinate=_coordinate;

- (id)initWithCoordinate:(CLLocationCoordinate2D)coordinate andID:(NSUInteger)pinID{
    self = [super init];
    if (self != nil) {
        _coordinate = coordinate;
        _pinID = pinID;
    }
    return self;
}

- (NSString *)title {
    return [NSString stringWithFormat:@"Pin %u", _pinID];
}

- (NSString *)subtitle {
    return [NSString stringWithFormat:@"%.4f, %.4f", _coordinate.latitude, _coordinate.longitude];
}

@end

然后，我尝试使用以下代码将其连接到我的地图

MapViewController.m

- (void)viewDidLoad
{
    [super viewDidLoad];
    CLLocationCoordinate2D coordinate;
    coordinate.latitude = 49.2802;
    coordinate.longitude = -123.1182;
    mapView.delegate = self;
    mapView.region = MKCoordinateRegionMakeWithDistance(coordinate, 2000, 2000); 


    CLLocationCoordinate2D newCoord = {2000, 2000};
    Annotation* annotation = [[Annotation alloc] initWithCoordinate:newCoord andID:1];
    [mapView addAnnotation:annotation];
}

但这并没有任何意义，针甚至没有显示。我究竟做错了什么？ 我寻求帮助和教训，但没有工作成果。

Answer 1

注释的坐标无效：

CLLocationCoordinate2D newCoord = {2000, 2000};
Annotation* annotation = [[Annotation alloc] initWithCoordinate:newCoord ...

纬度，经度2000,2000无效。

您可能希望使用coordinate变量（您在viewDidLoad中定义了几行）：

Annotation* annotation = [[Annotation alloc] initWithCoordinate:coordinate andID:1];

Answer 2

试试这个

- (void)viewDidLoad
{
    [super viewDidLoad];
    CLLocationCoordinate2D coordinate;
    coordinate.latitude = 49.2802;
    coordinate.longitude = -123.1182;
    mapView.delegate = self;
    mapView.region = MKCoordinateRegionMakeWithDistance(coordinate, 2000, 2000); 

    Annotation* annotation = [[Annotation alloc] initWithCoordinate:coordinate andID:1];
    [mapView addAnnotation:annotation];
}