ios - CMMotionManager deviceMotion 姿态值过多 "flickering"

Question

我正在记录从 CMMotionManager deviceMotion 获得的“态度”值在 CADisplayLink 回调中(我需要根据设备旋转执行动画)。

这些值似乎每隔几毫秒就会有很大程度的“抽动”(高达 30%)。这看起来很不稳定，让我想知道是我做错了什么还是设备出了问题。

请在下面找到日志。打印出来的“角度”是“姿态”的“滚动”分量，换算成度数:


<br/>2013-04-10 00:07:12.683 MyApp[450:707] Angle: -92.91
<br/>2013-04-10 00:07:12.712 MyApp[450:707] Angle: -70.52
<br/>2013-04-10 00:07:12.714 MyApp[450:707] Angle: -92.25
<br/>2013-04-10 00:07:12.745 MyApp[450:707] Angle: -70.03
<br/>2013-04-10 00:07:12.747 MyApp[450:707] Angle: -91.74
<br/>2013-04-10 00:07:12.779 MyApp[450:707] Angle: -69.67
<br/>2013-04-10 00:07:12.784 MyApp[450:707] Angle: -91.23
<br/>2013-04-10 00:07:12.812 MyApp[450:707] Angle: -69.43
<br/>2013-04-10 00:07:12.815 MyApp[450:707] Angle: -91.19
<br/>2013-04-10 00:07:12.846 MyApp[450:707] Angle: -69.53
<br/>2013-04-10 00:07:12.849 MyApp[450:707] Angle: -91.33
<br/>2013-04-10 00:07:12.879 MyApp[450:707] Angle: -69.74
<br/>2013-04-10 00:07:12.881 MyApp[450:707] Angle: -91.57
<br/>2013-04-10 00:07:12.912 MyApp[450:707] Angle: -70.01
<br/>2013-04-10 00:07:12.915 MyApp[450:707] Angle: -91.85
<br/>2013-04-10 00:07:12.945 MyApp[450:707] Angle: -70.13
<br/>2013-04-10 00:07:12.949 MyApp[450:707] Angle: -91.99
<br/>2013-04-10 00:07:12.979 MyApp[450:707] Angle: -70.03
<br/>2013-04-10 00:07:12.983 MyApp[450:707] Angle: -91.93
<br/>2013-04-10 00:07:13.012 MyApp[450:707] Angle: -69.76
<br/>2013-04-10 00:07:13.016 MyApp[450:707] Angle: -91.71
<br/>2013-04-10 00:07:13.046 MyApp[450:707] Angle: -69.34
<br/>2013-04-10 00:07:13.051 MyApp[450:707] Angle: -91.19
<br/>2013-04-10 00:07:13.079 MyApp[450:707] Angle: -68.89
<br/>2013-04-10 00:07:13.082 MyApp[450:707] Angle: -90.94
<br/>2013-04-10 00:07:13.112 MyApp[450:707] Angle: -68.52
<br/>2013-04-10 00:07:13.114 MyApp[450:707] Angle: -90.66
<br/>2013-04-10 00:07:13.151 MyApp[450:707] Angle: -67.85
<br/>2013-04-10 00:07:13.156 MyApp[450:707] Angle: -89.47
<br/>2013-04-10 00:07:13.179 MyApp[450:707] Angle: -65.66
<br/>2013-04-10 00:07:13.181 MyApp[450:707] Angle: -88.10
<br/>2013-04-10 00:07:13.212 MyApp[450:707] Angle: -63.81
<br/>2013-04-10 00:07:13.216 MyApp[450:707] Angle: -86.33
<br/>2013-04-10 00:07:13.245 MyApp[450:707] Angle: -61.07
<br/>2013-04-10 00:07:13.248 MyApp[450:707] Angle: -83.63
<br/>2013-04-10 00:07:13.279 MyApp[450:707] Angle: -58.95
<br/>2013-04-10 00:07:13.282 MyApp[450:707] Angle: -81.46
<br/>2013-04-10 00:07:13.312 MyApp[450:707] Angle: -56.71
<br/>2013-04-10 00:07:13.314 MyApp[450:707] Angle: -79.06
<br/>2013-04-10 00:07:13.346 MyApp[450:707] Angle: -53.29
<br/>2013-04-10 00:07:13.350 MyApp[450:707] Angle: -75.23
<br/>2013-04-10 00:07:13.380 MyApp[450:707] Angle: -51.63
<br/>2013-04-10 00:07:13.383 MyApp[450:707] Angle: -73.37
<br/>2013-04-10 00:07:13.414 MyApp[450:707] Angle: -50.35
<br/>2013-04-10 00:07:13.418 MyApp[450:707] Angle: -72.11
<br/>2013-04-10 00:07:13.446 MyApp[450:707] Angle: -50.08
<br/>2013-04-10 00:07:13.450 MyApp[450:707] Angle: -72.01
<br/>2013-04-10 00:07:13.479 MyApp[450:707] Angle: -50.50
<br/>2013-04-10 00:07:13.488 MyApp[450:707] Angle: -73.51
<br/>2013-04-10 00:07:13.512 MyApp[450:707] Angle: -51.25
<br/>2013-04-10 00:07:13.514 MyApp[450:707] Angle: -74.14
<br/>2013-04-10 00:07:13.545 MyApp[450:707] Angle: -49.98
<br/>2013-04-10 00:07:13.547 MyApp[450:707] Angle: -72.96
<br/>2013-04-10 00:07:13.579 MyApp[450:707] Angle: -46.99
<br/>2013-04-10 00:07:13.582 MyApp[450:707] Angle: -68.58
<br/>2013-04-10 00:07:13.612 MyApp[450:707] Angle: -43.01
<br/>2013-04-10 00:07:13.616 MyApp[450:707] Angle: -65.32
<br/>2013-04-10 00:07:13.645 MyApp[450:707] Angle: -40.92
<br/>2013-04-10 00:07:13.647 MyApp[450:707] Angle: -62.80
<br/>2013-04-10 00:07:13.680 MyApp[450:707] Angle: -39.70
<br/>2013-04-10 00:07:13.683 MyApp[450:707] Angle: -61.30
<br/>2013-04-10 00:07:13.712 MyApp[450:707] Angle: -40.74
<br/>2013-04-10 00:07:13.714 MyApp[450:707] Angle: -63.06
<br/>2013-04-10 00:07:13.745 MyApp[450:707] Angle: -42.29
<br/>2013-04-10 00:07:13.747 MyApp[450:707] Angle: -65.68
<br/>2013-04-10 00:07:13.779 MyApp[450:707] Angle: -43.18
<br/>2013-04-10 00:07:13.780 MyApp[450:707] Angle: -67.58
<br/>2013-04-10 00:07:13.812 MyApp[450:707] Angle: -42.13
<br/>2013-04-10 00:07:13.815 MyApp[450:707] Angle: -66.35
<br/>2013-04-10 00:07:13.845 MyApp[450:707] Angle: -40.95
<br/>2013-04-10 00:07:13.848 MyApp[450:707] Angle: -64.67
<br/>2013-04-10 00:07:13.879 MyApp[450:707] Angle: -39.73
<br/>2013-04-10 00:07:13.881 MyApp[450:707] Angle: -62.90
<br/>2013-04-10 00:07:13.913 MyApp[450:707] Angle: -40.06
<br/>2013-04-10 00:07:13.916 MyApp[450:707] Angle: -63.12
<br/>2013-04-10 00:07:13.947 MyApp[450:707] Angle: -40.78
<br/>2013-04-10 00:07:13.949 MyApp[450:707] Angle: -63.39
<br/>2013-04-10 00:07:13.979 MyApp[450:707] Angle: -41.51
<br/>2013-04-10 00:07:13.981 MyApp[450:707] Angle: -62.78
<br/>2013-04-10 00:07:14.012 MyApp[450:707] Angle: -42.06
<br/>2013-04-10 00:07:14.014 MyApp[450:707] Angle: -61.77
<br/>2013-04-10 00:07:14.045 MyApp[450:707] Angle: -43.89
<br/>2013-04-10 00:07:14.047 MyApp[450:707] Angle: -61.02
<br/>2013-04-10 00:07:14.079 MyApp[450:707] Angle: -45.41
<br/>2013-04-10 00:07:14.080 MyApp[450:707] Angle: -61.20
<br/>2013-04-10 00:07:14.112 MyApp[450:707] Angle: -46.93
<br/>2013-04-10 00:07:14.114 MyApp[450:707] Angle: -61.53
<br/>2013-04-10 00:07:14.146 MyApp[450:707] Angle: -49.21
<br/>2013-04-10 00:07:14.147 MyApp[450:707] Angle: -62.76
<br/>2013-04-10 00:07:14.179 MyApp[450:707] Angle: -51.34
<br/>2013-04-10 00:07:14.182 MyApp[450:707] Angle: -64.51
<br/>2013-04-10 00:07:14.212 MyApp[450:707] Angle: -53.39
<br/>2013-04-10 00:07:14.214 MyApp[450:707] Angle: -66.41
<br/>2013-04-10 00:07:14.245 MyApp[450:707] Angle: -56.29
<br/>2013-04-10 00:07:14.248 MyApp[450:707] Angle: -69.30
<br/>2013-04-10 00:07:14.279 MyApp[450:707] Angle: -57.85
<br/>2013-04-10 00:07:14.280 MyApp[450:707] Angle: -70.88
<br/>2013-04-10 00:07:14.312 MyApp[450:707] Angle: -60.23


测量的角度每隔几毫秒“闪烁”近 20 度。根据我到目前为止所读到的关于 CoreMotion 的内容，我预计会出现错误，但不会在这个范围内。

我是否可能做错了什么 - 我没有测量正确的东西吗？



编辑:下面的代码 - 对格式感到抱歉。 “code”和“blockquote”似乎都不能正常工作。

//I'm letting the user laze around a bit before starting the motion updates.
//At the moment this is in the form of a naive idle timer which is fired after
//the first 9 seconds of launching the app (just cause)


- (void)didFireIdleTimer:(id)theTimer {

[mReferenceAttitude release];
mReferenceAttitude = [[[sSharedMotionManager deviceMotion] attitude] retain];

[self stopIdleTimer];
}

//sSharedMotionManager is an instance of CMMotionManager

//Then, I'm setting up a display link callback wherein the "current" deviceMotion
//is retrieved every time and the difference between the current "attitude"
//and reference "attitude" calculated. It is this difference that is
//converted to degrees and printed

//This is the display link callback, lazily named. :)
- (void)didRefreshScreen:(id)sender {

CMAttitude *thisAttitude = [[sSharedMotionManager deviceMotion] attitude];
[thisAttitude multiplyByInverseOfAttitude:mReferenceAttitude];

NSLog(@"Angle: %0.2f", thisAttitude.roll * 180 / 3.14159);

//Rest of the code
//....
}

Answer 1

几个小时的测试确认问题的出现是因为 deviceMotionUpdateInterval 没有在 CMMotionManager 实例上设置。将其设置为 1.0/60.0(或任何其他有效值)可修复此“闪烁”并导致值平滑变化。