用户位置的Objective-C的MKMapView中心

问题描述：

我试图放大到用户位置为画面中心的参考。我有这个code：

I'm trying to zoom into the user location as the center reference for the screen. I have this code:

MainViewController.h

#import <UIKit/UIKit.h>
#import "FlipsideViewController.h"
#import <MapKit/MapKit.h>
#import <CoreLocation/CoreLocation.h>

IBOutlet MKMapView *mapView;

@interface MainViewController : UIViewController <FlipsideViewControllerDelegate, MKMapViewDelegate> {
   MKMapView *mapView;
}
@property (nonatomic, retain) IBOutlet MKMapView *mapView;

MainViewController.m

@implementation MainViewController
@synthesize mapView;

 - (void)viewDidLoad {
    [super viewDidLoad];
    mapView = [[MKMapView alloc]
           initWithFrame:self.view.bounds
           ];
    mapView.showsUserLocation = YES;
    mapView.mapType = MKMapTypeHybrid;
    mapView.delegate = self;
    [self.view addSubview:mapView];
}

- (void)mapView:(MKMapView *)mapView didUpdateUserLocation:(MKUserLocation *)userLocation {
    MKCoordinateRegion region;
    MKCoordinateSpan span;
    span.latitudeDelta = 0.005;
    span.longitudeDelta = 0.005;
    CLLocationCoordinate2D location;
    location.latitude = userLocation.coordinate.latitude;
    location.longitude = userLocation.coordinate.longitude;
    region.span = span;
    region.center = location;
    [mapView setRegion:region animated:YES];
 }

现在我只得到一个建立在最后一行警告 [图形页面setRegion：地区动画：是] 指出：图形页面'的局部声明隐藏了实例变量

Now I'm only getting a build warning on the last line [mapView setRegion:region animated:YES] stating: 'local declaration of 'mapView' hides instance variable'

答

当你做 mapView.showsUserLocation = YES; ，你问它来获取用户的位置。这不会即刻发生。由于需要时间，地图视图通知其委托该用户的位置通过委托方法mapView:didUpdateUserLocation$c$c>.所以，你应该采用 MKMapViewDelegate 的协议和实施方法。您应该所有的移近code移动到这个方法。

When you do mapView.showsUserLocation = YES;, you ask it to retrieve the user location. This doesn't happen instantly. As it takes time, the map view notifies its delegate that a user location is available via the delegate method mapView:didUpdateUserLocation. So you should adopt the MKMapViewDelegate protocol and implement that method. You should move all your zooming-in code to this method.

设置委托

- (void)viewDidLoad {
    [super viewDidLoad];
    mapView = [[MKMapView alloc]
           initWithFrame:CGRectMake(0, 
                                    0,
                                    self.view.bounds.size.width, 
                                    self.view.bounds.size.height)
           ];
    mapView.showsUserLocation = YES;
    mapView.mapType = MKMapTypeHybrid;
    mapView.delegate = self;
    [self.view addSubview:mapView];
}

更新的委托方法

- (void)mapView:(MKMapView *)aMapView didUpdateUserLocation:(MKUserLocation *)aUserLocation {
    MKCoordinateRegion region;
    MKCoordinateSpan span;
    span.latitudeDelta = 0.005;
    span.longitudeDelta = 0.005;
    CLLocationCoordinate2D location;
    location.latitude = aUserLocation.coordinate.latitude;
    location.longitude = aUserLocation.coordinate.longitude;
    region.span = span;
    region.center = location;
    [aMapView setRegion:region animated:YES];
}

用户位置的Objective-C的MKMapView中心

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