简单磁力计实现（指南针）

- (void)viewDidLoad

{

    [superviewDidLoad];

    

    

    UIImageView * ima = [[UIImageViewalloc]initWithImage:[UIImageimageNamed:@"2.png"]];

    ima.frame =CGRectMake(0,0, 200, 200);

    ima.center =self.view.center;

    [self.viewaddSubview:ima];

    

    _imageView = [[UIImageViewalloc]initWithImage:[UIImageimageNamed:@"3.png"]];

    _imageView.backgroundColor = [UIColorclearColor];

    _imageView.frame =CGRectMake(0,0, 35, 200);

    _imageView.center = ima.center;

    [self.viewaddSubview:_imageView];

    [_imageViewrelease];

    

    self.locatioManager = [[CLLocationManageralloc]init];

    self.locatioManager.delegate =self;

    

   //判断传感器是否可用

    if ([CLLocationManagerheadingAvailable]) {

        //设置精度

       self.locatioManager.desiredAccuracy =kCLLocationAccuracyBest;

       //设置滤波器不工作

       self.locatioManager.headingFilter =kCLHeadingFilterNone;

        //开始更新

        [self.locatioManagerstartUpdatingHeading];

        

    }

    

    

    

    

    

  

  

    

    // Do any additional setup after loading the view.

}

- (void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading{

   //每次要重置view的位置,才能保证图片每次偏转量正常,而不是叠加,指针方向正确

    _imageView.transform =CGAffineTransformIdentity;

    CGAffineTransform transform = CGAffineTransformMakeRotation(-1 *M_PI * newHeading.magneticHeading/180.0);

    

      // CGAffineTransform transform = CGAffineTransformMakeTranslation(10, 50);

    _imageView.transform = transform;

}