Android
Sensors

 Modified: 11/14/2014 10:16:27

Resources

http://webhole.net/2011/08/20/android-sdk-accelerometer-example-tutorial/ - Very basic accelerometer example.

http://www.vogella.de/articles/AndroidSensor/article.html - Accelerometer tutorial.

http://www.vogella.de/articles/AndroidLocationAPI/article.html - Location and map example.

http://android-er.blogspot.com/2011/02/get-list-of-available-sensors.html - Sensor list example.

Overview

Android devices have a variety of sensors and timers, including:

Android Timer Example

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Video

System.currentTimeMillis() gives the current wall-clock time in milliseconds.

mHandler.postDelayed(this, 1000) re-executes the mUpdateElapsedTimeTask Runnable object after a 1000 ms. delay.

mHandler.removeCallbacks(mUpdateElapsedTimeTask) removes any existing callbacks for mUpdateElapsedTimeTask.

TimerUpdatingActivity.java 
package edu.ius.rwisman.TimerUpdating;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.TextView;

public class TimerUpdatingActivity extends Activity {
	private Handler mHandler = new Handler();
	long mStartTime;
	TextView mTimeLabel;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		mTimeLabel = (TextView) findViewById(R.id.time);
	}

	private Runnable mUpdateElapsedTimeTask = new Runnable() {
		public void run() {
			final long start = mStartTime;
			long millis = System.currentTimeMillis() - start;

			mTimeLabel.setText("" + millis);
								// Re-execute after 1000 ms.
			mHandler.postDelayed(this, 1000);		
		}
	};

	public void Start(View v) {
		mStartTime = System.currentTimeMillis();
		mHandler.removeCallbacks(mUpdateElapsedTimeTask);
		mHandler.postDelayed(mUpdateElapsedTimeTask, 0);
	}

	public void Stop(View v) {
		mHandler.removeCallbacks(mUpdateElapsedTimeTask);
	}
}

 

Android Sensors

List all sensors

The following list all available sensors on the Xoom device.

SensorList.java 
package edu.ius.rwisman.SensorList;

import java.util.ArrayList;
import java.util.List;
import android.app.ListActivity;
import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.widget.ArrayAdapter;

public class SensorListActivity extends ListActivity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        
        SensorManager sensorManager = (SensorManager)getSystemService(Context.SENSOR_SERVICE);

        List listSensor = sensorManager.getSensorList(Sensor.TYPE_ALL);

        List listSensorType = new ArrayList();
        
        for(int i=0; i<listSensor.size(); i++)
        	listSensorType.add(listSensor.get(i).getName());
        
        setListAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, listSensorType));
        
        getListView().setTextFilterEnabled(true);
    }
}

 

Sensors are accessed in a generic way by implementing SensorEventListener and registering as a listener to a specific Sensor type.

A ServiceManager is acquired via getSystemService(SENSOR_SERVICE) which can register a SensorEventListener.

As a SensorEventListener two methods must be implemented that receive callbacks:

public void onAccuracyChanged(Sensor sensor, int accuracy)

public void onSensorChanged(SensorEvent event)

 

GenericSensorExample.java 
  public class SensorActivity extends Activity implements SensorEventListener {

     private final SensorManager mSensorManager;
     private final Sensor mGenericSensor;

     public SensorActivity() {
         mSensorManager = (SensorManager)getSystemService(SENSOR_SERVICE);

         mGenericSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_GENERIC);
     }

     protected void onResume() {
         super.onResume();
         mSensorManager.registerListener(this, mGenericSensor, SensorManager.SENSOR_DELAY_NORMAL);
     }

     protected void onPause() {
         super.onPause();
         mSensorManager.unregisterListener(this);
     }

     public void onAccuracyChanged(Sensor sensor, int accuracy) {
     }

     public void onSensorChanged(SensorEvent event) {
     }
 }

To avoid the unnecessary usage of battery, register the listener in the onResume method and de-register on the onPause method.

Android Temperature Example

For devices with a temperature sensor, specified by Sensor.TYPE_TEMPERATURE, the following displays the current temperature as changes occur.

TemperatureActivity.java 
package edu.ius.rwisman.Temperature;

import android.app.Activity;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.widget.TextView;

public class TemperatureActivity extends Activity implements SensorEventListener {

    private SensorManager mSensorManager;
    private Sensor mTemperature;
    private TextView mTemperatureLabel;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mTemperatureLabel = (TextView) findViewById(R.id.temperature);

       mSensorManager = (SensorManager)getSystemService(SENSOR_SERVICE);

       mTemperature = mSensorManager.getDefaultSensor(Sensor.TYPE_TEMPERATURE);
    }

    protected void onResume() {
        super.onResume();
        mSensorManager.registerListener(this, mTemperature, SensorManager.SENSOR_DELAY_NORMAL);
    }

    protected void onPause() {					// Turn off sensor when not in use.
        super.onPause();
        mSensorManager.unregisterListener(this);
    }

    public void onAccuracyChanged(Sensor sensor, int accuracy) {}

    public void onSensorChanged(SensorEvent event) {	// Check for temperature sensor callback
           if (event.sensor.getType() != Sensor.TYPE_TEMPERATURE) return;

    	mTemperatureLabel.setText(""+mTemperature.getPower());
    }
}

 

Android Accelerometer Example

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The accelerometer values are represented in SI units (m/s2). The device at right has the bottom of the device screen pointing toward the center of gravity.  Gravity on Earth is 9.80665 m/s2.

AccelerometerSimpleExample.java 
package edu.ius.rwisman.AccelerometerSimpleExample;

import android.app.Activity;
import android.graphics.Color;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.widget.TextView;
import android.widget.Toast;

public class AccelerometerSimpleExampleActivity extends Activity implements SensorEventListener {
	private SensorManager sensorManager;
	private boolean color = false; 
	private View view;
	private long lastUpdate;
	TextView xCoor; 
	TextView yCoor;
	TextView zCoor;

	@Override
	public void onCreate(Bundle savedInstanceState){
		requestWindowFeature(Window.FEATURE_NO_TITLE);
		getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
	                                             WindowManager.LayoutParams.FLAG_FULLSCREEN);
	  
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		view = findViewById(R.id.textView);
		view.setBackgroundColor(Color.GREEN);

		xCoor=(TextView)findViewById(R.id.xcoor);
		yCoor=(TextView)findViewById(R.id.ycoor);
		zCoor=(TextView)findViewById(R.id.zcoor);
		
		sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);

		sensorManager.registerListener( this,
				sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),
				SensorManager.SENSOR_DELAY_NORMAL);
		lastUpdate = System.currentTimeMillis();
	}

	@Override
	public void onSensorChanged(SensorEvent event) {
		if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
			float[] values = event.values;

			float x = values[0];
			float y = values[1];
			float z = values[2];
			
			xCoor.setText("X: "+x);
			yCoor.setText("Y: "+y);
			zCoor.setText("Z: "+z);

			float accelerationSquareRoot = (x * x + y * y + z * z) / 
                                                   (SensorManager.GRAVITY_EARTH * SensorManager.GRAVITY_EARTH);
			long actualTime = System.currentTimeMillis();
			
			if (accelerationSquareRoot >= 2)  {
				if (actualTime - lastUpdate < 200)  return;

				lastUpdate = actualTime;
				Toast.makeText(this, "Device was shaken", Toast.LENGTH_SHORT).show();
				if (color)  view.setBackgroundColor(Color.GREEN);
				else view.setBackgroundColor(Color.RED);
				color = !color;
			}
		}
	}

	@Override
	public void onAccuracyChanged(Sensor sensor, int accuracy) { }

	@Override
	protected void onResume() {
		super.onResume();
									// register as a listener for orientation and
									// accelerometer sensors
		sensorManager.registerListener( this,
				sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),
				SensorManager.SENSOR_DELAY_NORMAL);
	}

	@Override
	protected void onPause() {					// unregister listener
		sensorManager.unregisterListener( this );
		super.onStop();
	}
}

main.xml supplies the plot area parameters.

main.xml 
<?xml version="1.0" encoding="utf-8"?>
<TableLayout
	xmlns:android="http://schemas.android.com/apk/res/android"
	android:layout_width="fill_parent"
	android:layout_height="fill_parent">

	<TableRow>
	<TextView android:id="@+id/textView" android:layout_width="match_parent"
		android:layout_height="match_parent" android:text="Shake to get a toast message and to switch color" />
	</TableRow>
    <TableRow>
	<TextView
		android:id="@+id/xcoor"
		android:text="X Coordinate: "
		android:layout_width="wrap_content"
		android:layout_height="wrap_content"
	/>
	</TableRow>
	<TableRow>
	<TextView
		android:id="@+id/ycoor"
		android:text="Y Coordinate: "
		android:layout_width="wrap_content"
		android:layout_height="wrap_content"
	/>
	</TableRow>
	<TableRow>
	<TextView
		android:id="@+id/zcoor"
		android:text="Z Coordinate: "
		android:layout_width="wrap_content"
		android:layout_height="wrap_content"
	/>
	</TableRow>
</TableLayout>

 

Location

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A LocationManager is acquired via getSystemService(Context.LOCATION_SERVICE) to access location.

A location (longitude, latitude) can be entered for the emulator by (at the command line):

telnet localhost 5554

geo fix -85.819 38.343

LocationActivity.java 
package edu.ius.rwisman.Location;
import android.app.Activity;
import android.content.Context;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.widget.TextView;
import android.widget.Toast;

public class LocationActivity extends Activity implements LocationListener {
	private TextView latitudeField;
	private TextView longitudeField;
	private LocationManager locationManager;
	private String provider;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		latitudeField = (TextView) findViewById(R.id.latitude);
		longitudeField = (TextView) findViewById(R.id.longitude);
										// Get the location manager
		locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
										// Criteria to select location provider
		Criteria criteria = new Criteria();
		provider = locationManager.getBestProvider(criteria, false);
		Location location = locationManager.getLastKnownLocation(provider);

		if (location != null) {
			System.out.println("Provider " + provider + " has been selected.");
			latitudeField.setText(location.getLatitude()+"");
			longitudeField.setText(location.getLongitude()+"");
			
		} else {
			latitudeField.setText("Provider not available");
			longitudeField.setText("Provider not available");
		}
	}
										// Request updates at startup
	@Override
	protected void onResume() {
		super.onResume();
		locationManager.requestLocationUpdates(provider, 400, 1, this);
	}
										// Remove LocationListener updates
	@Override
	protected void onPause() {
		super.onPause();
		locationManager.removeUpdates(this);
	}

	@Override
	public void onLocationChanged(Location location) {
		latitudeField.setText(location.getLatitude()+"");
		longitudeField.setText(location.getLongitude()+"");
	}

	@Override
	public void onStatusChanged(String provider, int status, Bundle extras) {	}

	@Override
	public void onProviderEnabled(String provider) {
		Toast.makeText(this, "Enabled provider " + provider, Toast.LENGTH_SHORT).show();
	}

	@Override
	public void onProviderDisabled(String provider) {
		Toast.makeText(this, "Disabled provider " + provider, Toast.LENGTH_SHORT).show();
	}
}
main.xml 
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:orientation="vertical" android:layout_width="fill_parent"
	android:layout_height="fill_parent">
	<LinearLayout android:id="@+id/linearLayout1"
		android:layout_height="wrap_content" android:layout_width="match_parent"
		android:orientation="horizontal" android:layout_marginTop="40dip">
		<TextView android:text="Latitude: " android:layout_height="wrap_content"
			android:layout_width="wrap_content" android:id="@+id/TextView01" 
			android:layout_marginLeft="10dip" android:layout_marginRight="5dip" android:textSize="20dip"></TextView>
		<TextView android:text="unknown" android:layout_height="wrap_content"
			android:layout_width="wrap_content" android:id="@+id/latitude" android:textSize="20dip"></TextView>
	</LinearLayout>
	<LinearLayout android:id="@+id/linearLayout2"
		android:layout_height="wrap_content" android:layout_width="match_parent">
		<TextView android:text="Longitude: " android:layout_height="wrap_content"
			android:layout_width="wrap_content" android:id="@+id/TextView03"
			android:layout_marginLeft="10dip" android:layout_marginRight="5dip" android:textSize="20dip"></TextView>
		<TextView android:text="unknown" android:layout_height="wrap_content"
			android:layout_width="wrap_content" android:id="@+id/longitude" android:textSize="20dip"></TextView>
	</LinearLayout>
</LinearLayout>
AndroidManifest.xml 
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="edu.ius.rwisman.Location"
    android:versionCode="1"
    android:versionName="1.0" >
    <uses-sdk android:minSdkVersion="13" />
    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:label="@string/app_name"
            android:name=".LocationActivity" >
            <intent-filter >
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
	</application>
	<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"></uses-permission>
	<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"></uses-permission>
	<uses-permission android:name="android.permission.INTERNET"></uses-permission>
</manifest>