Devicemotion没有更新值

Question

我不知道为什么当记录时，滚动、俯仰和偏航值为0.0000。我确信这是我错过的一件事，但我想不出。

这是代码：

//ViewController.m

#import "ViewController.h"
@interface ViewController (){

}
@property (nonatomic) CMMotionManager *motionManager;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.motionManager = [[CMMotionManager alloc] init];
    CMDeviceMotion *devMotion = [[CMDeviceMotion alloc]init];

    if ([self.motionManager isDeviceMotionAvailable]) {
        NSLog(@"Device Motion Available");
        [self.motionManager setDeviceMotionUpdateInterval:1.0/30.0];
        // Pull mechanism is used
        [self.motionManager startDeviceMotionUpdates];
    }
    devMotion = self.motionManager.deviceMotion;

    NSLog(@"Roll Pitch and Yaw are %f, %f, %f",devMotion.attitude.roll, devMotion.attitude.pitch, devMotion.attitude.yaw);

}

我已经研究过类似的问题了：SO Question

请帮我理解一下..。

谢谢..

更新代码：

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.motionManager = [[CMMotionManager alloc] init];

    if ([self.motionManager isDeviceMotionAvailable]) {
        NSLog(@"Device Motion Available");
        [self.motionManager setDeviceMotionUpdateInterval:1.0/30.0];
        // Pull mechanism is used
        [self.motionManager startDeviceMotionUpdates];
    }
    CMDeviceMotion *devMotion = self.motionManager.deviceMotion;
    NSLog(@"*Roll,Pitch and Yaw are %f, %f, %f",devMotion.attitude.roll, devMotion.attitude.pitch, devMotion.attitude.yaw);

    self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0/30.0 target:self selector:@selector(updateValues:) userInfo:nil repeats:YES];
}

-(void) updateValues:(NSTimer *)timer{
    CMDeviceMotion *currDeviceMotion = self.motionManager.deviceMotion;

    NSLog(@"Roll Pitch and Yaw are %f, %f, %f",currDeviceMotion.attitude.roll, currDeviceMotion.attitude.pitch, currDeviceMotion.attitude.yaw);


}

此代码的大部分初始值为0.000000。从那以后它开始获得价值..。因此，我想startDeviceMotionUpdates在向deviceMotion提供值方面存在一些延迟。所以看起来我需要弄清楚如何保存第一个非零值。

Answer 1

• 请注意，devMotion变量不会立即保存可用的值(或任何值)，因为CMMotionManager需要一段时间才能在startDeviceMotionUpdates之后更新deviceMotion属性。因此，您应该有某种定期触发并读取该属性的计时器。你的链接文章做了一些类似的事情。
  • 只要陀螺仪启动，deviceMotion属性将为null (您只看到0.0，因为nil的消息返回零)。

​

• 作为一个sidenote:您对[[CMDeviceMotion alloc] init]的调用是无用的，因为您随后用self.motionManager.deviceMotion重写了结果分配给的变量。