高仿系统指南针，方向数据是地磁航向数据，有定位地理位置信息和地磁方向信息，可以和系统的指南针对比看一看。
一、运行效果
二、实现过程
1.继承于UIView创建一个带刻度标注的视图ScaleView，利用UIBezierPath和CAShapeLayer、UILabel，默认0刻度(北)在最上方。
//化刻度表- (void)paintingScale{ CGFloat perAngle = M_PI/(90); NSArray *array = @[@"北",@"东",@"南",@"西"]; //画圆环，每隔2°画一个弧线，总共180条 for (int i = 0; i < 180; i++) { CGFloat startAngle = (-(M_PI_2+M_PI/180/2)+perAngle*i); CGFloat endAngle = startAngle+perAngle/2; UIBezierPath *bezPath = [UIBezierPath bezierPathWithArcCenter:CGPointMake(self.frame.size.width/2, self.frame.size.height/2) radius:(self.frame.size.width/2 - 50) startAngle:startAngle endAngle:endAngle clockwise:YES]; CAShapeLayer *shapeLayer = [CAShapeLayer layer]; //每隔30°画一个白条刻度 if (i%15 == 0) { shapeLayer.strokeColor = [[UIColor whiteColor] CGColor]; shapeLayer.lineWidth = 20; }else{ shapeLayer.strokeColor = [[UIColor grayColor] CGColor]; shapeLayer.lineWidth = 10; } shapeLayer.path = bezPath.CGPath; shapeLayer.fillColor = [UIColor clearColor].CGColor; [_backgroundView.layer addSublayer:shapeLayer]; //每隔30°画一个刻度的标注 0 30 60... if (i % 15 == 0){ NSString *tickText = [NSString stringWithFormat:@"%d",i * 2]; CGFloat textAngel = startAngle+(endAngle-startAngle)/2; CGPoint point = [self calculateTextPositonWithArcCenter:CGPointMake(self.frame.size.width/2, self.frame.size.height/2) Angle:textAngel andScale:1.2]; UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(point.x, point.y, 30, 15)]; label.center = point; label.text = tickText; label.textColor = [UIColor whiteColor]; label.font = [UIFont systemFontOfSize:15]; label.textAlignment = NSTextAlignmentCenter; [_backgroundView addSubview:label]; //标注 北 东 南 西 if (i%45 == 0){ tickText = array[i/45]; CGPoint point2 = [self calculateTextPositonWithArcCenter:CGPointMake(self.frame.size.width/2, self.frame.size.height/2) Angle:textAngel andScale:0.8]; UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(point2.x, point2.y, 30, 20)]; label.center = point2; label.text = tickText; label.textColor = [UIColor whiteColor]; label.font = [UIFont systemFontOfSize:20]; label.textAlignment = NSTextAlignmentCenter; if ([tickText isEqualToString:@"北"]) { UILabel * markLabel = [[UILabel alloc]initWithFrame:CGRectMake(point.x, point.y, 8, 8)]; markLabel.center = CGPointMake(point.x, point.y + 12); markLabel.clipsToBounds = YES; markLabel.layer.cornerRadius = 4; markLabel.backgroundColor = [UIColor redColor]; [_backgroundView addSubview:markLabel]; } [_backgroundView addSubview:label]; } } } //画十字线，参照线 UIView * levelView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.frame.size.width/2/2, 1)]; levelView.center = CGPointMake(self.frame.size.width/2, self.frame.size.height/2); levelView.backgroundColor = [UIColor whiteColor]; [self addSubview:levelView]; UIView * verticalView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 1, self.frame.size.width/2/2)]; verticalView.center = CGPointMake(self.frame.size.width/2, self.frame.size.height/2); verticalView.backgroundColor = [UIColor whiteColor]; [self addSubview:verticalView]; UIView * lineView = [[UIView alloc] initWithFrame:CGRectMake(self.frame.size.width/2 -1.5, self.frame.size.height/2 - (self.frame.size.width/2 - 50) - 50, 3, 30 + 30)]; lineView.backgroundColor = [UIColor whiteColor]; [self addSubview:lineView];}复制代码 2、利用CLLocationManager初始化定位装置，并设置代理 ，记得在info.plist中加入隐私定位权限关键字 Privacy - Location When In Use Usage Description
// 注意开启手机的定位服务，隐私那里的 self.locationManager = [[CLLocationManager alloc]init]; self.locationManager.delegate=self; // 定位频率,每隔多少米定位一次 // 距离过滤器，移动了几米之后，才会触发定位的代理函数 self.locationManager.distanceFilter = 0; // 定位的精度，越精确，耗电量越高 self.locationManager.desiredAccuracy = kCLLocationAccuracyBestForNavigation;//导航 //请求允许在前台获取用户位置的授权 [self.locationManager requestWhenInUseAuthorization]; //允许后台定位更新,进入后台后有蓝条闪动 self.locationManager.allowsBackgroundLocationUpdates = YES; //判断定位设备是否能用和能否获得导航数据 if ([CLLocationManager locationServicesEnabled]&&[CLLocationManager headingAvailable]){ [self.locationManager startUpdatingLocation];//开启定位服务 [self.locationManager startUpdatingHeading];//开始获得航向数据 } else{ NSLog(@"不能获得航向数据"); }复制代码 通过实现定位装置的代理方法： -(void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading 来获得地理和地磁航向数据，从而转动地理刻度表以及表上的文字标注； 方法-(BOOL)locationManagerShouldDisplayHeadingCalibration:(CLLocationManager *)manager返回Yes是为了受到外来磁场干扰时，设备会自动进行校验。
#pragma mark - CLLocationManagerDelegate//获得地理和地磁航向数据，从而转动地理刻度表-(void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading{ //获得当前设备 UIDevice *device =[UIDevice currentDevice]; // 判断磁力计是否有效,负数时为无效，越小越精确 if (newHeading.headingAccuracy>0) { //地磁航向数据-》magneticHeading float magneticHeading =[self heading:newHeading.magneticHeading fromOrirntation:device.orientation]; //地理航向数据-》trueHeading float trueHeading =[self heading:newHeading.trueHeading fromOrirntation:device.orientation]; //地磁北方向 float heading = -1.0f *M_PI *newHeading.magneticHeading /180.0f; _angleLabel.text = [NSString stringWithFormat:@"%3.1f°",magneticHeading]; //旋转变换 [_scaView resetDirection:heading]; //返回当前手机（摄像头)朝向方向 [self updateHeading:newHeading]; }}//判断设备是否需要校验，受到外来磁场干扰时-(BOOL)locationManagerShouldDisplayHeadingCalibration:(CLLocationManager *)manager{ return YES;}//旋转重置刻度标志的方向- (void)resetDirection:(CGFloat)heading{ _backgroundView.transform = CGAffineTransformMakeRotation(heading); for (UILabel * label in _backgroundView.subviews) { label.transform = CGAffineTransformMakeRotation(-heading); }}复制代码 3、通过代理方法获得经纬度以及海拔数据，然后利用经纬度进行地理反编码获得地理位置信息。
// 定位成功之后的回调方法，只要位置改变，就会调用这个方法- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations{ self.currLocation = [locations lastObject]; //维纬度 NSString * latitudeStr = [NSString stringWithFormat:@"%3.2f", _currLocation.coordinate.latitude]; //经度 NSString * longitudeStr = [NSString stringWithFormat:@"%3.2f", _currLocation.coordinate.longitude]; //高度 NSString * altitudeStr = [NSString stringWithFormat:@"%3.2f", _currLocation.altitude]; NSLog(@"纬度 %@ 经度 %@ 高度 %@", latitudeStr, longitudeStr, altitudeStr); _latitudlongitudeLabel.text = [NSString stringWithFormat:@"纬度：%@ 经度：%@ 海拔：%@", latitudeStr, longitudeStr, altitudeStr]; CLGeocoder *geocoder = [[CLGeocoder alloc] init]; [geocoder reverseGeocodeLocation:self.currLocation completionHandler:^(NSArray *placemarks, NSError *error) { if ([placemarks count] > 0) { CLPlacemark *placemark = placemarks[0]; NSDictionary *addressDictionary = placemark.addressDictionary; NSString *street = [addressDictionary objectForKey:(NSString *)kABPersonAddressStreetKey]; street = street == nil ? @"": street; NSString *country = placemark.country; NSString * subLocality = placemark.subLocality; NSString *city = [addressDictionary objectForKey:(NSString *)kABPersonAddressCityKey]; city = city == nil ? @"": city; NSLog(@"%@",[NSString stringWithFormat:@"%@ \n%@ \n%@ %@ ",country, city,subLocality ,street]); _positionLabel.text = [NSString stringWithFormat:@" %@\n %@ %@%@ " ,country, city,subLocality ,street]; } }];}复制代码 示例Github：
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