Professional Android Sensor Programming

Chapter 8

Detecting Movement

What's in this chapter?

Explaining the difference between the accelerometer and the linear acceleration sensor

Introducing some of the issues involved with using acceleration data in Android

Providing a method to smooth acceleration data

Providing a functional example of acceleration data being collected and processed to detect device movement

Chapter 7 discussed ways to determine the current orientation of a device using the gravity sensor and SensorManager.getOrientation(). This chapter discusses methods to detect device movement using the accelerometer and the linear acceleration sensor. Although both sensors provide acceleration data, the data has differences that may make one sensor preferable over the other in certain situations. This chapter illustrates the differences in how the acceleration data is represented for each sensor.

To aid in illustrating the use of these sensors, this chapter provides an example in the form of a motion detector that uses Text-To-Speech to indicate when device movement is detected. The example app in this chapter will be provided sensor information in a similar manner to the way sensor data was read in Chapter 7. The main difference is the actual sensors that are used in this chapter—the accelerometer and the linear acceleration sensor. As explained in Chapter 5, the accelerometer provides raw acceleration data for the X, Y, and Z axes, and the linear acceleration is a synthetic sensor that performs processing on ...