iOS使用CoreLocation实现指南针

#import 

@interface ViewController ()

@property (nonatomic ,strong) CLLocationManager *mgr;
// 指南针图片
@property (nonatomic, strong) UIImageView *compassView;

@end

@implementation ViewController

#pragma mark - 
- (CLLocationManager *)mgr
{
    if (!_mgr) {
        _mgr = [[CLLocationManager alloc] init];
    }
    return _mgr;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    
    _compassView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"compass.png"]];
    _compassView.center = CGPointMake(self.view.frame.size.width/2, self.view.frame.size.height/2);
    [self.view addSubview: _compassView];
    
    // 设置代理监听获取到的位置
    self.mgr.delegate = self;
    
    // 开始获取用户位置（获取用户的方向信息不需要用户授权）
    [self.mgr startUpdatingHeading];
}

// 当获取到用户方向时就会调用
- (void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading
{
    // 将获取到的角度转为弧度 (角度 * π) / 180;
    CGFloat angle = newHeading.magneticHeading * M_PI / 180;
    
    NSLog(@"angle = %f",angle);
    // 旋转图片
    self.compasspointer.transform = CGAffineTransformMakeRotation(-angle);
}