实际上非常简单，只需使用参考框架开始生成设备动作更新：

Its quite simple actually, just start generating device motion updates using a reference frame:

- (void)startDeviceMotionUpdatesUsingReferenceFrame:(CMAttitudeReferenceFrame)referenceFrame

根据您想要达到的目的，您可以选择其中一个不同的选项

Depending on what you want to achieve you can select one of the different options

typedef enum {
   CMAttitudeReferenceFrameXArbitraryZVertical = 1 << 0,
   CMAttitudeReferenceFrameXArbitraryCorrectedZVertical = 1 << 1,
   CMAttitudeReferenceFrameXMagneticNorthZVertical = 1 << 2,
   CMAttitudeReferenceFrameXTrueNorthZVertical = 1 << 3
} CMAttitudeReferenceFrame;

例如，通过使用CMAttitudeReferenceFrameXMagneticNorthZVertical，您从加速度获得的读数将是恒定的，无论设备位置（它们与重力对齐前方和北方）。我不记得确切的参考位置，但我相信手机顶部指向北方，而手机屏幕指向up。

For example, by using "CMAttitudeReferenceFrameXMagneticNorthZVertical" the readings you get from the acceleration would be constant regardless of the device position (they get aligned with "gravity" bellow" and "north" in front). I don't remember the exact reference position but i believe the "top of the phone" points north while the "screen of the phone" points up.