IOS 特定于设备的开发:Core Motion基础

@property (nonatomic , strong)CMMotionManager *motionManager;


 _motionManager = [[CMMotionManager alloc]init];
    //监测陀螺仪
    if(_motionManager.gyroAvailable)
    {
        [_motionManager startGyroUpdates];
    }
    
    //监测磁力计
    if(_motionManager.magnetometerAvailable)
    {
        [_motionManager startMagnetometerUpdates];
    }
    
    //监测重力感应器
    if(_motionManager.accelerometerAvailable)
    {
        [_motionManager startAccelerometerUpdates];
    }
    
    //监测Device Motion
    if(_motionManager.deviceMotionAvailable)
    {
        [_motionManager startDeviceMotionUpdates];
    }

@implementation TestBedViewController
{
    UIImageView *butterfly;
    
    float xaccel;
    float xvelocity;
    float yaccel;
    float yvelocity;
    
    float mostRecentAngle;
    
    CMMotionManager *motionManager;
    NSTimer *timer;
}

- (void) tick
{
    butterfly.transform = CGAffineTransformIdentity;
    
    // Move the butterfly according to the current velocity vector
    CGRect rect = CGRectOffset(butterfly.frame, xvelocity, 0.0f);
    if (CGRectContainsRect(self.view.bounds, rect))
        butterfly.frame = rect;
    
    rect = CGRectOffset(butterfly.frame, 0.0f, yvelocity);
    if (CGRectContainsRect(self.view.bounds, rect))
        butterfly.frame = rect;
    
    butterfly.transform = CGAffineTransformMakeRotation(mostRecentAngle + M_PI_2);
}

- (void) shutDownMotionManager
{
    NSLog(@"Shutting down motion manager");
    [motionManager stopAccelerometerUpdates];
    motionManager = nil;
    
    [timer invalidate];
    timer = nil;
}

- (void) establishMotionManager
{
    if (motionManager)
        [self shutDownMotionManager];
    
    NSLog(@"Establishing motion manager");
    
    // Establish the motion manager
    motionManager = [[CMMotionManager alloc] init];
    if (motionManager.accelerometerAvailable)
        [motionManager
         startAccelerometerUpdatesToQueue:[[NSOperationQueue alloc] init]
         withHandler:^(CMAccelerometerData *data, NSError *error)
         {
             // extract the acceleration components
             float xx = -data.acceleration.x;
             float yy = data.acceleration.y;
             mostRecentAngle = atan2(yy, xx);
             
             // Has the direction changed?
             float accelDirX = SIGN(xvelocity) * -1.0f;
             float newDirX = SIGN(xx);
             float accelDirY = SIGN(yvelocity) * -1.0f;
             float newDirY = SIGN(yy);
             
             // Accelerate. To increase viscosity lower the additive value
             if (accelDirX == newDirX) xaccel = (abs(xaccel) + 0.85f) * SIGN(xaccel);
             if (accelDirY == newDirY) yaccel = (abs(yaccel) + 0.85f) * SIGN(yaccel);
             
             // Apply acceleration changes to the current velocity
             xvelocity = -xaccel * xx;
             yvelocity = -yaccel * yy;
         }];
    
    
    // Start the physics timer
    timer = [NSTimer scheduledTimerWithTimeInterval: 0.03f target: self selector: @selector(tick) userInfo: nil repeats: YES];
}

- (void) initButterfly
{
    CGSize size;
    
    // Load the animation cells
    NSMutableArray *butterflies = [NSMutableArray array];
    for (int i = 1; i <= 17; i++)
    {
        NSString *fileName = [NSString stringWithFormat:@"bf_%d.png", i];
        UIImage *image = [UIImage imageNamed:fileName];
        size = image.size;
        [butterflies addObject:image];
    }
    
    // Begin the animation
    butterfly = [[UIImageView alloc] initWithFrame:(CGRect){.size=size}];
    [butterfly setAnimationImages:butterflies];
    butterfly.animationDuration = 0.75f;
    [butterfly startAnimating];
    
    // Set the butterfly‘s initial speed and acceleration
    xaccel = 2.0f;
    yaccel = 2.0f;
    xvelocity = 0.0f;
    yvelocity = 0.0f;
    
    // Add the butterfly
    butterfly.center = RECTCENTER(self.view.bounds);
    [self.view addSubview:butterfly];
}

- (void) loadView
{
    [super loadView];
    self.view.backgroundColor = [UIColor whiteColor];
    [self initButterfly];
}