iphone - 获取 iPhone 当前位置的最简单方法是什么？

Question

我已经知道如何使用 CLLocationManager，所以我可以用委托(delegate)等困难的方式来完成它。

但我想要一个方便的方法，只需获取当前位置一次，然后阻塞直到获得结果。

Answer 1

我所做的是实现一个单例类来管理来自核心位置的更新。要访问我的当前位置，我执行 CLLocation *myLocation = [[LocationManager sharedInstance] currentLocation]; 如果您想阻止主线程，您可以执行以下操作:

while ([[LocationManager sharedInstance] locationKnown] == NO){
   //blocking here
   //do stuff here, dont forget to have some kind of timeout to get out of this blocked    //state
}

但是，正如已经指出的那样，阻塞主线程可能不是一个好主意，但是当您正在构建某些东西时，这可能是一个很好的起点。您还会注意到，我编写的类会检查位置更新的时间戳并忽略任何旧的时间戳，以防止从核心位置获取过时数据的问题。

这是我写的单例类。请注意，它的边缘有点粗糙:

#import <CoreLocation/CoreLocation.h>
#import <Foundation/Foundation.h>

@interface  LocationController : NSObject <CLLocationManagerDelegate> {
    CLLocationManager *locationManager;
    CLLocation *currentLocation;
}

+ (LocationController *)sharedInstance;

-(void) start;
-(void) stop;
-(BOOL) locationKnown;

@property (nonatomic, retain) CLLocation *currentLocation;

@end
@implementation LocationController

@synthesize currentLocation;

static LocationController *sharedInstance;

+ (LocationController *)sharedInstance {
    @synchronized(self) {
        if (!sharedInstance)
            sharedInstance=[[LocationController alloc] init];       
    }
    return sharedInstance;
}

+(id)alloc {
    @synchronized(self) {
        NSAssert(sharedInstance == nil, @"Attempted to allocate a second instance of a singleton LocationController.");
        sharedInstance = [super alloc];
    }
    return sharedInstance;
}

-(id) init {
    if (self = [super init]) {
        self.currentLocation = [[CLLocation alloc] init];
        locationManager = [[CLLocationManager alloc] init];
        locationManager.delegate = self;
        [self start];
    }
    return self;
}

-(void) start {
    [locationManager startUpdatingLocation];
}

-(void) stop {
    [locationManager stopUpdatingLocation];
}

-(BOOL) locationKnown { 
     if (round(currentLocation.speed) == -1) return NO; else return YES; 
}

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
    //if the time interval returned from core location is more than two minutes we ignore it because it might be from an old session
    if ( abs([newLocation.timestamp timeIntervalSinceDate: [NSDate date]]) < 120) {     
        self.currentLocation = newLocation;
    }
}

- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error {
    UIAlertView *alert;
    alert = [[UIAlertView alloc] initWithTitle:@"Error" message:[error description] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [alert show];
    [alert release];
}

-(void) dealloc {
    [locationManager release];
    [currentLocation release];
    [super dealloc];
}

@end