Basic Sensors in iOS

Writing an Accelerometer Application

Let’s go ahead and implement a simple application to illustrate how to approach the accelerometer. Open Xcode and start a new View-based application for the iPhone, and name the project “Accelerometer” when prompted for a filename.

Warning

The raw accelerometer data can also be accessed using the Core Motion framework, which was new in iOS 4.0. I talk about how to do this in Chapter 6. It is therefore possible, even likely, that the UIAccelerometer class discussed in this chapter my be deprecated in a future iOS release.

Click on the AccelerometerViewController.xib file to open it into Interface Builder. Since you want to both report the raw figures from the accelerometer and also display them using a progress bar, go ahead and drag and drop three UIProgressView controls 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 accelerometer measurements. After you do that, the view should look something a lot like Figure 4-2.

Figure 4-2. The Accelerometer application UI

Go ahead and close the Utilities panel and click to open the Assistant Editor. Then Control-Click and drag from the three UIProgressView elements, and the three UILabel elements to the AcclerometerViewController.h header file. The header file should be displayed in the Assistant Editor ...