How to find your current location with CoreLocatio

问题:

I need to find my current location with CoreLocation, I tried multiple methods but so far my CLLocationManager has only returned 0's.. (0.000.00.000).

Here's my code (updated to work):

Imports:

#import <CoreLocation/CoreLocation.h>

Declared:

IBOutlet CLLocationManager *locationManager;
IBOutlet UILabel *latLabel;
IBOutlet UILabel *longLabel;

Functions:

- (void)getLocation { //Called when needed
    latLabel.text  = [NSString stringWithFormat:@"%f", locationManager.location.coordinate.latitude]; 
    longLabel.text = [NSString stringWithFormat:@"%f", locationManager.location.coordinate.longitude];
}

- (void)viewDidLoad {
    locationManager = [[CLLocationManager alloc] init];
    locationManager.distanceFilter = kCLDistanceFilterNone; // whenever we move
    locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters; // 100 m
    [locationManager startUpdatingLocation];
}

回答1:

You can find your location using CoreLocation like this:

import CoreLocation:

#import <CoreLocation/CoreLocation.h>

Declare CLLocationManager:

CLLocationManager *locationManager;

Initialize the locationManager in viewDidLoad and create a function that can return the current location as an NSString:

- (NSString *)deviceLocation {
    return [NSString stringWithFormat:@"latitude: %f longitude: %f", locationManager.location.coordinate.latitude, locationManager.location.coordinate.longitude];
}

- (void)viewDidLoad
{
    locationManager = [[CLLocationManager alloc] init];
    locationManager.distanceFilter = kCLDistanceFilterNone; // whenever we move
    locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters; // 100 m
    [locationManager startUpdatingLocation];
}

And calling the deviceLocation function will return the location as expected:

NSLog(@"%@", [self deviceLocation]);

This is just an example. Initializing CLLocationManager without the user being ready for it isn't a good idea. And, of course, locationManager.location.coordinate can be used to get latitude and longitude at will after CLLocationManager has been initialized.

Don't forget to add the CoreLocation.framework in your project settings under the Build Phases tab (Targets->Build Phases->Link Binary).

回答2:

With CLLocationManager you don't necessary get the location information immediately. The GPS and other devices that obtain location information might not be initialized. They can take a while before they have any information. Instead you need to create a delegate object that responds to locationManager:didUpdateToLocation:fromLocation: and then set it as the delegate of the location manager.

see here

回答3:

Here you can show current location with annotation details

in ViewController.h

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


//My
#import <MapKit/MapKit.h>
#import <MessageUI/MFMailComposeViewController.h>

@interface ViewController : UIViewController<CLLocationManagerDelegate,MKMapViewDelegate,MFMailComposeViewControllerDelegate>
{
    IBOutlet UILabel *lblLatitiude;
    IBOutlet UILabel *lblLongitude;
    IBOutlet UILabel *lblAdress;
}
//My
@property (nonatomic, strong) IBOutlet MKMapView *mapView;


-(IBAction)getMyLocation:(id)sender;

@end

in ViewController.m

#import "ViewController.h"


@interface ViewController ()

@end

@implementation ViewController{
    CLLocationManager *locationManager;
    CLGeocoder *geocoder;
    CLPlacemark *placemark;
}

@synthesize mapView;

- (void)viewDidLoad
{
    [super viewDidLoad];
    locationManager = [[CLLocationManager alloc] init];
     geocoder = [[CLGeocoder alloc] init];

    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    NSMutableDictionary *defaultsDictionary = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"[e-mail]", @"fromEmail",
                                               @"[e-mail]", @"toEmail",
                                               @"smtp.gmail.com", @"relayHost",
                                               @"[e-mail]", @"login",
                                               @"mobile@123", @"pass",
                                               [NSNumber numberWithBool:YES], @"requiresAuth",
                                               [NSNumber numberWithBool:YES], @"wantsSecure", nil];

    [userDefaults registerDefaults:defaultsDictionary];


    self.mapView.delegate=self;

}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark - Custom Methods


-(IBAction)getMyLocation:(id)sender{
    locationManager.delegate = self;
    locationManager.desiredAccuracy = kCLLocationAccuracyBest;

    [locationManager startUpdatingLocation];
}


#pragma mark - CLLocationManagerDelegate

- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
    NSLog(@"didFailWithError: %@", error);
    UIAlertView *errorAlert = [[UIAlertView alloc]
                               initWithTitle:@"Error" message:@"Failed to Get Your Location" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [errorAlert show];
}

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
    NSLog(@"didUpdateToLocation: %@", newLocation);
    CLLocation *currentLocation = newLocation;

    if (currentLocation != nil) {
        lblLongitude.text = [NSString stringWithFormat:@"%.8f", currentLocation.coordinate.longitude];
        lblLatitiude.text = [NSString stringWithFormat:@"%.8f", currentLocation.coordinate.latitude];
    }

    // Stop Location Manager
    [locationManager stopUpdatingLocation];

    // Reverse Geocoding
    NSLog(@"Resolving the Address");
    [geocoder reverseGeocodeLocation:currentLocation completionHandler:^(NSArray *placemarks, NSError *error) {
        NSLog(@"Found placemarks: %@, error: %@", placemarks, error);
        if (error == nil && [placemarks count] > 0) {
            placemark = [placemarks lastObject];

            lblAdress.text = [NSString stringWithFormat:@"%@ %@\n%@ %@\n%@\n%@",
                                 placemark.subThoroughfare, placemark.thoroughfare,
                                 placemark.postalCode, placemark.locality,
                                 placemark.administrativeArea,
                                 placemark.country];



            MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance(currentLocation.coordinate, 800, 800);
            [self.mapView setRegion:[self.mapView regionThatFits:region] animated:YES];

            // Add an annotation
            MKPointAnnotation *point = [[MKPointAnnotation alloc] init];
            point.coordinate = currentLocation.coordinate;
            point.title = @"Where am I?";
            point.subtitle = [NSString stringWithFormat:@"%@ %@\n%@ %@\n%@\n%@",
                              placemark.subThoroughfare, placemark.thoroughfare,
                              placemark.postalCode, placemark.locality,
                              placemark.administrativeArea,
                              placemark.country];


            [self.mapView addAnnotation:point];


        } else {
            NSLog(@"%@", error.debugDescription);
        }
    } ];


}

//My
- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation
{
    MKAnnotationView *annotationView = [[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:@"loc"];
    annotationView.canShowCallout = YES;
    annotationView.rightCalloutAccessoryView = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];

    return annotationView;
}

- (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:(UIControl *)control
{

    [self getSignScreenShot];

    MFMailComposeViewController* controller = [[MFMailComposeViewController alloc] init];
    controller.mailComposeDelegate = self;
    [controller setSubject:@"My Subject"];
    [controller setMessageBody:@"Hello there." isHTML:NO];
    if (controller) [self presentModalViewController:controller animated:YES];
}

- (void)mailComposeController:(MFMailComposeViewController*)controller
          didFinishWithResult:(MFMailComposeResult)result
                        error:(NSError*)error;
{
    if (result == MFMailComposeResultSent) {
        NSLog(@"It's away!");
    }
    [self dismissModalViewControllerAnimated:YES];
}

//-----------------------------------------------------------------------------------
//This methos is to take screenshot of map
//-----------------------------------------------------------------------------------
-(UIImage *)getSignScreenShot
{
    CGRect rect = CGRectMake(self.mapView.frame.origin.x,self.mapView.frame.origin.y-50,self.mapView.frame.size.width+60,self.mapView.frame.size.height+15);
    UIGraphicsBeginImageContextWithOptions(self.mapView.frame.size, NO, 1.0);
    [self.mapView.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();
    CGImageRef imageRef = CGImageCreateWithImageInRect([screenshot CGImage], rect);
    UIImage *newImage = [UIImage imageWithCGImage:imageRef];

    return newImage;
}