16.3. Retrieving Accelerometer Data

Problem

You want to ask iOS to send accelerometer data to your application.

Solution

Use the startAccelerometerUpdatesToQueue:withHandler: instance method of CMMotionManager. Here is the header file of a view controller that utilizes CMMotionManager to get accelerometer updates:

#import <UIKit/UIKit.h>
#import <CoreMotion/CoreMotion.h>

@interface Retrieving_Accelerometer_DataViewController : UIViewController

@property (nonatomic, strong) CMMotionManager *motionManager;

@end

We will now implement our view controller and take advantage of the startAccelerometerUpdatesToQueue:withHandler: method of the CMMotionManager class:

#import "Retrieving_Accelerometer_DataViewController.h" @implementation Retrieving_Accelerometer_DataViewController @synthesize motionManager; - (void)viewDidLoad{ [super viewDidLoad]; self.motionManager = [[CMMotionManager alloc] init]; if ([self.motionManager isAccelerometerAvailable]){ NSOperationQueue *queue = [[NSOperationQueue alloc] init]; [self.motionManager startAccelerometerUpdatesToQueue:queue withHandler:^(CMAccelerometerData *accelerometerData, NSError *error) { NSLog(@"X = %.04f, Y = %.04f, Z = %.04f", accelerometerData.acceleration.x, accelerometerData.acceleration.y, accelerometerData.acceleration.z); }]; } else { NSLog(@"Accelerometer is not available."); } } - (void)viewDidUnload{ [super viewDidUnload]; self.motionManager = nil; } - (BOOL)shouldAutorotateToInterfaceOrientation :(UIInterfaceOrientation)interfaceOrientation{ ...

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