如何根据加速度计让 UIImageView 始终面朝上？

Question

我想做到这一点，以便当用户旋转设备（到任何角度，而不仅仅是横向/纵向）时， UIImageView 将始终朝上。我该怎么做？

提前致谢

Answer 1

@interface FirstViewController : UIViewController <UIAccelerometerDelegate> {
    IBOutlet UIImageView *imageView;
    CGPoint delta;
    CGPoint translation;
    float ballRadius;  
}

//implementation

- (void)viewDidLoad
{    
    [super viewDidLoad];

    // for the line in the middle of the camera
    UIAccelerometer *accel = [UIAccelerometer sharedAccelerometer];
    accel.delegate = self;
    accel.updateInterval = 1.0f/60.0f;        
}

- (void)accelerometer:(UIAccelerometer *)acel
        didAccelerate:(UIAcceleration *)acceleration {

    // Get the current device angle
    float xx = -[acceleration x]; 
    float yy = [acceleration y]; 
    float angle = atan2(yy, xx); 

    // Add 1.5 to the angle to keep the image constantly horizontal to the viewer.
    [imageView setTransform:CGAffineTransformMakeRotation(angle+1.5)]; 

}