Basic Sensors in iOS

Measuring Device Motion

Let’s go ahead and build a similar application to the one above, but this time reporting the data exposed by the CMDeviceMotion object:

CMAttitude *attitude = motionData.attitude;
CMAcceleration gravity = motionData.gravity;
CMAcceleration userAcceleration = motionData.userAcceleration;
CMRotationRate rotate = motionData.rotationRate;

Open Xcode and start a new iPhone project, select a View-based Application template, and name the project “Motion” when prompted for a filename. As before, import the Core Motion framework into the project and then click on the MotionViewController.xib file to open it in Interface Builder, and then proceed to drag-and-drop UIProgressBar and UILabel elements into your View in a similar manner as you did for the Gyroscope application earlier in the chapter. You’ll need labels for the yaw, pitch and roll values, along with progress bars and labels for the user acceleration, gravity and rotation values.

Once you’ve done this, go ahead and connect the various bars and labels as IBOutlet using the Assistant Editor into the MotionViewController.h interface file as in Figure 6-5.

Figure 6-5. The Motion application UI with the IBOutlet connected in Interface Builder to the MotionViewController.h interface file

Once you’ve done this, save your changes and open up the MotionViewController.h interface file in the Standard Editor. Go ahead and ...