To follow this recipe, create a new project called Accelerometer. Similar to the previous recipe, you'll have to deploy your code on a physical phone as the emulator doesn't support the accelerometer.

Now, we will see how to use the accelerometer and other sensors:

Each sensor's data can be accessed through background services. In order for our application to be fed by the data of a sensor, we need to create a reference to the SensorManager instance. Finally, we can register our application via a Listener instance, so the OnSensorChanged()method will be triggered every time the sensor changes its value.

To acquire a reference to the SensorManager instance, we simply use the GetSystemService() helper as follows:

mySensorManager = (SensorManager) GetSystemService(SensorService);

Then, we register our application to receive the data from the accelerometer as follows:

mySensorManager.RegisterListener(this, mySensorManager.GetDefaultSensor(SensorType.Accelerometer),
SensorDelay.Ui);

In the OnSensorChanged() method, we implemented a C# thread-safe lock as this method can be retriggered before it finishes its execution:

lock (myLock)

Then, we retrieve the values of the acceleration for the three axes and compare them with the previous values. If the division results is more than two (value of accelerometer) on one of the three axes, it likely means that the phone is falling:

float currentX = e.Values [0];
float currentY = e.Values [1];
float currentZ = e.Values [2];

// First time
if (z == 0 && y == 0 && z == 0) {

  z = currentZ;
  y = currentY;
  x = currentX;

}
else if (Math.Abs (currentX / x) > 2 || Math.Abs (currentY / y) > 2 || Math.Abs (currentZ / z) > 2) {
  z = currentZ;
  y = currentY;
  x = currentX;

  text.Append ("Is Probably Falling");
}

Android phones can be equipped with a very large range of sensors that can be used in the same way as the accelerator. They are categorized in three categories: motion, position, and environment. For each of them, you'll have to register your activity as follows:

mySensorManager.RegisterListener(this, mySensorManager.GetDefaultSensor(SensorType.MY_TYPE),
SensorDelay.MY_FREQ);

Here SensorType.MY_TYPE and SensorType.MY_FREQ have to be adapted to your needs.

While we can easily discover the different sensors using the Intellisense of Xamarin, the data they return is only float. In what follows, I report what those floats represent.

protected override void OnResume() {
  base.OnResume();
  mySensorManager.RegisterListener(this, mySensorManager.GetDefaultSensor(SensorType.Accelerometer),
  SensorDelay.Ui);
}

protected override void OnPause() {
  base.OnPause();
  mySensorManager.UnregisterListener(this);
}

You can also visit the following links to learn how the values of these sensors are computed: