xcode 使用 UIButton 的 CLLocationManager startUpdatingLocation

CLLocationManager startUpdatingLocation using a UIButton

提问by Neelesh

This is the first time I am using CLLocationManager. I am not sure if i am doing the right thing. Correct me if i am wrong.

这是我第一次使用CLLocationManager. 我不确定我是否在做正确的事情。如果我错了，请纠正我。

I initialize the locationManager in my viewDidLoadMethod and tell the locationManager to startUpdatingLocation in the same method.

我在我的viewDidLoad方法中初始化 locationManager并告诉 locationManager 在相同的方法中 startUpdatingLocation 。

When the delegate receives

当委托人收到

-(void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation{

    [locationManager stopUpdatingLocation];
    //do stuff with the coordinates
}

to avoid repeated calls to this delegate method.

以避免重复调用此委托方法。

I have a UIButtonwhere users can click to update the location

我有一个UIButton用户可以点击更新位置的地方

//called by user action
-(IBAction)updateLocation{
    //start updating delegate
    locationManager.delegate=self;
    [locationManager startUpdatingLocation];    
}

However when the location changes and when I click the UIbutton, the location coordinates donot change at all. :(

但是，当位置发生变化并且我单击 时UIbutton，位置坐标根本不会发生变化。:(

What am i doing wrong? Is this the right of doing or should i not stop the locationManager at all ?

我究竟做错了什么？这是正确的做法还是我根本不应该停止 locationManager？

Help would be appreciated.

帮助将不胜感激。

回答by GarlicFries

CLLocationManagercaches your last location and returns it as soon as you call -startUpdatingLocation. So, you are starting updates, receiving the old location, and then stopping updates.

CLLocationManager缓存您的最后一个位置并在您调用-startUpdatingLocation. 因此，您开始更新，接收旧位置，然后停止更新。

This isn't how -startUpdatingLocation/-stopUpdatingLocationare meant to be used. As I asked above, what's wrong with calling the delegate method multiple times? If you only want to get the location when the user taps a button, leave the CLLocationManagerupdating, and just check CLLocationManger's locationproperty when the user taps your button.

这不是应该如何-startUpdatingLocation/-stopUpdatingLocation使用。正如我上面所问的，多次调用委托方法有什么问题？如果您只想在用户点击按钮时获取位置，请保留CLLocationManager更新，并在用户点击您的按钮时检查CLLocationManger的location属性。

If the reason you're trying to avoid multiple calls to the delegate method is because you're worried about power consumption, etc., adjust the desiredAccuracyproperty of the CLLocationManagerwith something like: locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters.

如果你想避免多次调用委托方法的原因是因为你担心功耗等，调整desiredAccuracy的性质CLLocationManager的东西，如：locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters。

All told, it might look something like this...

总而言之，它可能看起来像这样......

.h file:

.h 文件：

@interface YourController : NSObject <CLLocationManagerDelegate>

@property (nonatomic, retain) CLLocationManager *locationMgr;
@property (nonatomic, retain) CLLocation *lastLocation;

- (IBAction)getNewLocation:(id)sender;

@end

.m file:

.m 文件：

@interface YourController

@synthesize locationMgr = _locationMgr;
@synthesize lastLocation = _lastLocation;

- (id)init
{
    if (self = [super init]) {
        self.locationMgr = [[CLLocationManager alloc] init];
        self.locationMgr.desiredAccuracy = kCLLocationAccuracyBest;
        self.locationMgr.delegate = self;
    }
    return self;
}

- (void)locationManager:(CLLocationManager *)manager 
    didUpdateToLocation:(CLLocation *)newLocation 
           fromLocation:(CLLocation *)oldLocation
{
    if (!self.lastLocation) {
        self.lastLocation = newLocation;        
    }

    if (newLocation.coordinate.latitude != self.lastLocation.coordinate.latitude &&
        newLocation.coordinate.longitude != self.lastLocation.coordinate.longitude) {        
        self.lastLocation = newLocation;
        NSLog(@"New location: %f, %f",
              self.lastLocation.coordinate.latitude,
              self.lastLocation.coordinate.longitude);
        [self.locationMgr stopUpdatingLocation];
    }
}

- (IBAction)getNewLocation:(id)sender
{
    [self.locationMgr startUpdatingLocation];
    NSLog(@"Old location: %f, %f", 
          self.lastLocation.coordinate.latitude, 
          self.lastLocation.coordinate.longitude);
}

- (void)dealloc
{
    [self.locationMgr release];
    self.locationMgr = nil;
    [self.lastLocation release];
    self.lastLocation = nil;
    [super dealloc];
}

@end

回答by Srikar Appalaraju

Am assuming you have included #import <CoreLocation/CoreLocation.h>framework to being with. This is the way you start getting location updates.

我假设你已经包含了#import <CoreLocation/CoreLocation.h>框架。这是您开始获取位置更新的方式。

CLLocationManager *locationMgr = [[CLLocationManager alloc] init];
locationMgr.desiredAccuracy = kCLLocationAccuracyBest;
locationMgr.delegate = self;

[locationMgr startUpdatingLocation];

You are correct here. After this you start getting location updates, here in this delegate-

你在这里是正确的。在此之后，您开始获取位置更新，在此委托中 -

-(void)locationManager:(CLLocationManager *)manager
   didUpdateToLocation:(CLLocation *)newLocation
   fromLocation:(CLLocation *)oldLocation
{
    // Handle location updates
} 

-(void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
    // Handle error
}