我可以使用此代码依赖此“默认”更新间隔（加速度计）吗？

Question

-(void)play
{
    CMMotionManager *motionManager = [[CMMotionManager alloc] init];
    [motionManager startDeviceMotionUpdates];

    while(!self.stopButtonPressed)
    {
        NSLog(@"Y-Axis acceleration is %f", motionManager.deviceMotion.userAcceleration.y);
    }
}

控制台：

2012-08-03 13:06:10.798 MyProject[8896:3a03] Y-Axis acceleration is 0.000000
2012-08-03 13:06:10.803 MyProject[8896:3a03] Y-Axis acceleration is 0.000000
2012-08-03 13:06:10.805 MyProject[8896:3a03] Y-Axis acceleration is 0.000000
2012-08-03 13:06:10.807 MyProject[8896:3a03] Y-Axis acceleration is 0.000000
2012-08-03 13:06:10.808 MyProject[8896:3a03] Y-Axis acceleration is 0.000000
2012-08-03 13:06:10.810 MyProject[8896:3a03] Y-Axis acceleration is 0.000000
2012-08-03 13:06:10.812 MyProject[8896:3a03] Y-Axis acceleration is 0.000000
2012-08-03 13:06:10.814 MyProject[8896:3a03] Y-Axis acceleration is 0.000000
2012-08-03 13:06:10.817 MyProject[8896:3a03] Y-Axis acceleration is 0.013498
2012-08-03 13:06:10.820 MyProject[8896:3a03] Y-Axis acceleration is 0.013498
2012-08-03 13:06:10.822 MyProject[8896:3a03] Y-Axis acceleration is 0.013498
2012-08-03 13:06:10.824 MyProject[8896:3a03] Y-Axis acceleration is 0.013498
2012-08-03 13:06:10.826 MyProject[8896:3a03] Y-Axis acceleration is 0.013498
2012-08-03 13:06:10.828 MyProject[8896:3a03] Y-Axis acceleration is 0.013498
2012-08-03 13:06:10.831 MyProject[8896:3a03] Y-Axis acceleration is -0.082339
2012-08-03 13:06:10.833 MyProject[8896:3a03] Y-Axis acceleration is -0.082339
2012-08-03 13:06:10.835 MyProject[8896:3a03] Y-Axis acceleration is -0.082339
2012-08-03 13:06:10.837 MyProject[8896:3a03] Y-Axis acceleration is -0.082339
2012-08-03 13:06:10.840 MyProject[8896:3a03] Y-Axis acceleration is -0.082339
2012-08-03 13:06:10.842 MyProject[8896:3a03] Y-Axis acceleration is -0.082339
2012-08-03 13:06:10.846 MyProject[8896:3a03] Y-Axis acceleration is -0.099570
2012-08-03 13:06:10.848 MyProject[8896:3a03] Y-Axis acceleration is -0.099570
2012-08-03 13:06:10.850 MyProject[8896:3a03] Y-Axis acceleration is -0.099570
2012-08-03 13:06:10.852 MyProject[8896:3a03] Y-Axis acceleration is -0.099570
2012-08-03 13:06:10.855 MyProject[8896:3a03] Y-Axis acceleration is -0.099570
2012-08-03 13:06:10.857 MyProject[8896:3a03] Y-Axis acceleration is -0.099570
2012-08-03 13:06:10.859 MyProject[8896:3a03] Y-Axis acceleration is -0.120698
2012-08-03 13:06:10.862 MyProject[8896:3a03] Y-Axis acceleration is -0.120698
2012-08-03 13:06:10.864 MyProject[8896:3a03] Y-Axis acceleration is -0.120698
2012-08-03 13:06:10.866 MyProject[8896:3a03] Y-Axis acceleration is -0.120698
2012-08-03 13:06:10.868 MyProject[8896:3a03] Y-Axis acceleration is -0.120698
2012-08-03 13:06:10.870 MyProject[8896:3a03] Y-Axis acceleration is -0.120698
2012-08-03 13:06:10.873 MyProject[8896:3a03] Y-Axis acceleration is -0.125984
2012-08-03 13:06:10.875 MyProject[8896:3a03] Y-Axis acceleration is -0.125984
2012-08-03 13:06:10.877 MyProject[8896:3a03] Y-Axis acceleration is -0.125984
2012-08-03 13:06:10.879 MyProject[8896:3a03] Y-Axis acceleration is -0.125984
2012-08-03 13:06:10.881 MyProject[8896:3a03] Y-Axis acceleration is -0.125984
2012-08-03 13:06:10.882 MyProject[8896:3a03] Y-Axis acceleration is -0.125984
2012-08-03 13:06:10.884 MyProject[8896:3a03] Y-Axis acceleration is -0.125984
2012-08-03 13:06:10.888 MyProject[8896:3a03] Y-Axis acceleration is -0.083223
....etc.

根据控制台，加速度值平均每 14 微秒更新一次

我没有明确使用具有更新间隔的队列，所以我是否应该假设默认更新间隔约为 14 微秒（当我在这段代码中专门从 while 循环中请求新值时）？

或者这是“意外”，我不应该依赖它？我的意思是我已经测试了几次，更新间隔总是在 13-14 毫秒之间，但是如果处理器在以后的一些测试中更新间隔有可能（如果我没有明确设置更新间隔）会发生显着变化当时出于某种原因碰巧“更忙”（比平时..）..？

感谢您的帮助

Answer 1

你不应该依赖这个间隔，因为来自UIAccelerometer 类参考 - 最大更新间隔基于可用的硬件，所以当苹果在未来的设备中更新加速度计芯片时，频率可能会改变（它也可以不同当前的 iPad 和 iPhone）