iOS开发手记－iOS8中使用定位服务解决方案

问题描述：

在iOS8之前，app第一次开始定位服务时，系统会弹出一个提示框来让用户选择是否允许使用定位信息。但iOS8后，app将不会出现这个弹窗。第一次运行之后，在设置->隐私->定位服务中，你的app没有任何设置，既不是“永不”，也不是“始终”。

代码如下：

#import "XYZFirstViewController.h"

@interface XYZFirstViewController ()
- (IBAction)LocateButtonClick:(id)sender;
@end

@implementation XYZFirstViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(startLocate) name:@"startLocateNotification" object:nil];
    _locationManager=[[CLLocationManager alloc] init];
    _locationManager.delegate=self;
    _locationManager.desiredAccuracy=kCLLocationAccuracyBest;
    _locationManager.distanceFilter=1000.0f;
    _mapView.mapType=MKMapTypeStandard;
    _mapView.delegate=self;
    
}

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

-(void) viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];
    [_locationManager startUpdatingLocation];
}

-(void) viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    [_locationManager stopUpdatingLocation];
}


-(void) locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
    CLLocation *currentLocation=[locations lastObject];
    _currentLocation=currentLocation;
    self.currentLocationLabel.text=[NSString stringWithFormat:@"%3.5f,%3.5f,%3.5f", currentLocation.coordinate.longitude,currentLocation.coordinate.latitude,currentLocation.altitude];
    MKCoordinateRegion region=MKCoordinateRegionMakeWithDistance(currentLocation.coordinate, 1000, 1000);
    [_mapView setRegion:region animated:YES];
    MKPointAnnotation *point=[[MKPointAnnotation alloc] init];
    point.coordinate=_currentLocation.coordinate;
    point.title=@"my location";
    [_mapView addAnnotation:point];
}

-(void) locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
    NSLog(@"error:%@",error);
}

/*
#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/

- (IBAction)LocateButtonClick:(id)sender {
    [[NSNotificationCenter defaultCenter] postNotificationName:@"startLocateNotification" object:self ];
}

-(void) startLocate
{
    CLGeocoder *geocoder=[[CLGeocoder alloc]init];
    [geocoder reverseGeocodeLocation:_currentLocation completionHandler:^(NSArray *placeMarks, NSError *error)
     {
        if([placeMarks count]>0)
        {
            NSLog(@"%@",placeMarks);
            CLPlacemark *placeMark=placeMarks[0];
            NSDictionary *addressDictonary=placeMark.addressDictionary;
            _currentAddressLabel.text=[NSString stringWithFormat:@"%@,%@,%@",[addressDictonary objectForKey:(NSString *)kABPersonAddressStateKey],[addressDictonary objectForKey:(NSString *)kABPersonAddressCityKey],[addressDictonary objectForKey:(NSString *) kABPersonAddressStreetKey] ];
        }
     }];
    
    
    
}
@end

解决方案：

以上代码在iOS8之后需要手动调用CLLocationManager对象的requestAlwaysAuthorization／

requestWhenInUseAuthorization方法。调用该方法需要在Info.plist中设置NSLocationAlwaysUsageDescription/NSLocationWhenInUseUsageDescription的值，这个值会显示在系统提示框中。

代码如下：

-(void) viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];
    [_locationManager requestWhenInUseAuthorization];
    [_locationManager startUpdatingLocation];
}

info.plist设置如下：