Sensing in Android

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# Implementing Sensing

Lauren Bricker

CSE 340 Spring 2022
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# Today's Agenda

- Administrivia
  - Undo due Fri 20-May
- Finish [Sensing and Reacting to the User](/courses/cse340/22sp/slides/wk08/ml.html#45)
- Sensing in practice
  - Review sensing and location
  - Implement sensing
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## Types of Sensors - Review

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<br><br>
![:img Picture of different sensors, 70%, width](img/ml/android-sensors.png)
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# Sensing: Categories of Sensors

* Motion Sensors
  * Measure acceleration forces and rotational forces along three axes
  * Includes accelerometers, gravity sensors, gyroscopes, and rotational vector sensor
  * Accelerometers and gyroscope are generally HW based, Gravity, linear acceleration, rotation
  vector, significant motion, step counter, and step detector may be HW or SW based
* Environmental Sensors
  * Measures relative ambient humidity, illuminance, ambient pressure, and ambient temperature
  * All four sensors are HW based
* Position Sensors
  * Determine the physical position of the device.
  * Includes orientation, magnetometers, and proximity sensors
  * Geomagnetic field sensor and proximity sensor are HW based

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# Sensing: Android Sensor Framework

`SensorManager` - Provides methods for accessing and listing sensors, registering and unregistering
sensor event listeners.

`Sensor` - A class to create an instance of a specific sensor. Can also be used to find a sensors abilities

`SensorEvent` - Contains information about a specific event from a sensor. Includes  the following
information: the raw sensor data, the type of sensor that generated the event, the accuracy of the
data, and the timestamp for the event.

`SensorEventListener` - Used to create callback methods to receive notifications about sensor events.

.footnote[[Sensor Framework](https://developer.android.com/guide/topics/sensors/sensors_overview#sensor-framework)]

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# Sensor Activity

The following slides are related to the
[Sensing and Location Activity](https://gitlab.cs.washington.edu/cse340/exercises/cse340-sensing-and-location)
that was introduced in Week 8 Lab

Clone this repo if you have not already.

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# Sensor Activity: SensorManager

Getting the `SensorManager`

```java
SensorManager mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
```

Getting the list of all `Sensor`s from the manager

```java
mSensorManager.getSensorList(Sensor.TYPE_ALL);
```

Getting a `Sensor` from the `SensorManager`. The `Sensor` type is a
[class constant](https://developer.android.com/guide/topics/sensors/sensors_overview#sensors-intro) in `Sensor`

```java
Sensor sensor = mSensorManager.getDefaultSensor(/* type of sensor */);
```

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# Sensor Activity: Sensor listeners

Create a `SensorEventListener` for use with the callback. For example:

```java
public class SensorActivity extends AbstractMainActivity implements SensorEventListener {
  public void onSensorChanged(SensorEvent event) {
    ...
    switch (event.sensor.getType()) {
      case Sensor.TYPE_AMBIENT_TEMPERATURE:
        ...
      case Sensor.TYPE_LINEAR_ACCELERATION:
      ...
    }
  }
  public void onAccuracyChanged(Sensor sensor, int accuracy) {
    // if Used
  }
}
```

You could use any of the ways to create a callback discussed earlier in this class.

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Registering the sensor. Done in `onResume` generally

```java
  Sensor sensor = mSensorManager.getDefaultSensor(/* type of sensor */);
  mSensorManager.registerListener(this, sensor, DELAY);
```

Make sure to unregister the listener in `onPause` so you're not working in the
background (unless that's the expected behavior)

```java
  mSensorManager.unregisterListener(this);
```

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# End of Deck