Basic Sensors in iOS

Accessing the Gyroscope

Let’s go ahead and implement a simple view-based application to illustrate how to use the gyroscope on its own before looking again at Core Motion and CMDeviceMotion. Open Xcode and start a new View-based Application iPhone project and name it “Gyroscope” when prompted for a filename.

Since we’ll be making use of the Core Motion framework, the first thing we need to do is add it to our new project. Click on the project file at the top of the Project navigator window on the right in Xcode, select the Target and click on the Build Phases tab, click on the Link with Libraries drop down and click on the + button to open the file pop-up window. Select CoreMotion.framework from the list of available frameworks and click the Add button.

Now go ahead and click on the GyroscopeViewController.xib file to open it in Interface Builder. As you did for the accelerometer back in Chapter 4, you’re going to build a simple interface to report the raw gyroscope readings. Go ahead and drag and drop three UIProgressView from the Object Library into the View window, then add two UILabel elements for each progress bar: one to hold the X, Y, or Z label and the other to hold the rotation measurements. After you do that, the view should look something a lot like Figure 6-1.

Figure 6-1. The Gyroscope UI

Go ahead and close the Utilities panel and click to open the Assistant Editor. Then Control-Click ...