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I have a view controller which is always in portrait. There is a certain feature which works according to the current orientation of the device itself, not orientation of the view controller.
How could I detect the device's orientation and trigger function on orientation changed in this case?

Vinh Hung Nguyen
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  • Do you mean you want to know which way gravity is, relative to the device? You can try using [`CMMotionManager.startDeviceMotionUpdates`](https://developer.apple.com/documentation/coremotion/cmmotionmanager/1616048-startdevicemotionupdates), and get `gravity` from it, which is a 3D vector. – Sweeper Sep 08 '21 at 08:18
  • you can achieve this by running CMMotionManager. [try this answer](https://stackoverflow.com/questions/49164302/get-current-ios-device-orientation-even-if-devices-orientation-locked) – MemetGhini Sep 08 '21 at 11:49

2 Answers2

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Since iOS 8 they introduced viewWillTransitionToSize that's triggered every time the rotation happens

- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator {
       [coordinator animateAlongsideTransition:^(id<UIViewControllerTransitionCoordinatorContext>  _Nonnull context) {
            UIInterfaceOrientation orientation = [[UIApplication sharedApplication] statusBarOrientation];
            // do what you need with orientation here
        } completion:^(id<UIViewControllerTransitionCoordinatorContext>  _Nonnull context) {
            
    }];
    [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];
}
Alastar
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you can achieve this by running CMMotionManager

#import <CoreMotion/CoreMotion.h>

#define DEGREES(x) (180.0 * x / M_PI)
#define RADIAN(x) (M_PI*x/180.0)
#define UPDATE_INTERVAL 0.3

typedef struct Point3D {
    CGFloat x, y, z;
} Point3D;

@interface DirectionListener()
{
    NSTimer * _motionTimer;
    CMMotionManager *_motionManager;
}
@end

@implementation DirectionListener

- (instancetype)init
{
    self = [super init];
    if (self) 
    {

    }
    return self;
}

- (void)dealloc 
{
    [self stopListenning];
    _motionManager = nil;
    if (_motionTimer) 
    {
        [_motionTimer invalidate];
        _motionTimer = nil;
    }
}

- (void)startListenning 
{
    if (_motionManager.deviceMotionActive) 
    {
        return;
    }
    if (!_motionManager) 
    {
        _motionManager = [[CMMotionManager alloc] init];
        _motionManager.deviceMotionUpdateInterval = UPDATE_INTERVAL;
    }
    [_motionManager startDeviceMotionUpdates];
    if (!_motionTimer) 
    {
        _motionTimer = [NSTimer scheduledTimerWithTimeInterval:UPDATE_INTERVAL target:self selector:@selector(changeWithAttitude) userInfo:nil repeats:YES];
    }
}

- (void)stopListenning {
    if (_motionManager.deviceMotionActive) 
    {
        [_motionManager stopDeviceMotionUpdates];
        [_motionTimer invalidate];
        _motionTimer = nil;
    }
}

-(void)changeWithAttitude 
{
    //get the value from motionManager there
}
MemetGhini
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