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2010-2011

   3D Compass

   3D Accelerometer

   Friction Tester

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Southside High School

Greenville, SC

public void onCreate(Bundle savedInstanceState)

{

      super.onCreate(savedInstanceState);

onCreate() is called at the start of the application. So we begin with some basics:

      //drawing

      draw = new Draw(this);

      draw2 = new Draw2(this);

      draw3 = new Draw3(this);

Creating and defining View objects to be used to later.

      //accel

      sensorManager = (SensorManager)
getSystemService(SENSOR_SERVICE);

      sensor = sensorManager.getDefaultSensor(Sensor.TYPE_ORIENTATION);

Setting up Accelerometer sensor.

      //GPS

      locationManager = (LocationManager)
getSystemService(LOCATION_SERVICE);

      Criteria criteria = new Criteria();

      criteria.setAccuracy(Criteria.ACCURACY_FINE);

      bestProvider = locationManager.getBestProvider(criteria, false);

Setting up GPS sensor (LocationManager).

      //layout

      LinearLayout view = new LinearLayout(this);

      view.setOrientation(LinearLayout.VERTICAL);

      LinearLayout topView = new LinearLayout(this);

      topView.setOrientation(LinearLayout.HORIZONTAL);

      topView.addView(draw3, 160, 185);

      topView.addView(draw2, 160, 185);

      view.addView(topView, 320, 185);

      view.addView(draw, 320, 245);

      setContentView(view);

}

The LinearLayout view encompasses both halves of the screen. The top half is draw and the bottom half is both draw2 and draw3. This is done by embedding another LinearLayout object topView inside view and adding draw2 and draw3 to that. So we have:

public void onPause()

{

      super.onPause();

      sensorManager.unregisterListener(this);

      locationManager.removeUpdates(this);

}

Unregister.

public void onResume()

{

      super.onResume();

      sensorManager.registerListener(this, sensor, rate);

      locationManager.requestLocationUpdates(

            bestProvider, 0, 0, this);

}

Register.

public void onSensorChanged(SensorEvent e)

{

      //update

      Base.accelValues[0] = e.values[0];

      Base.accelValues[1] = (-1*Math.abs(e.values[2])+90)/90;

      Base.accelValues[2] = (-1*Math.abs(e.values[1])+90)/90;

      draw.invalidate();

      draw2.invalidate();

      draw3.invalidate();

}

Update accelerometer values

public void onLocationChanged(Location location)

{

      if(location != null)

      Base.location = new Coordinate(location.getLongitude(), location.getLatitude());

}

Update GPS values.

public class Draw extends ImageView

{

      Paint paint;

      Bitmap compass;

Note that unlike the other classes, ImageView is used here in order to easily incorporate the image to be used for the compass.

      public Draw(Context context)

      {

            super(context);

            paint = new Paint();

            compass = BitmapFactory.
                  decodeResource(
                  context.getResources(),
                  R.drawable.compass);

      }

Accessing the image as a resource. It is stored under Compass (project) -> res -> drawable -> compass.jpg.

      public void onDraw(Canvas g)

      {

            super.onDraw(g);

            g.drawColor(Color.WHITE);

The onDraw() here acts the same as the paint() method from a JPanel. However the paint object acts as a helper here.

            g.scale(Base.accelValues[1], Base.accelValues[2], Base.width/2, Base.height/2);

            g.rotate(-1*Base.accelValues[0], Base.width/2, Base.height/2);

            g.drawBitmap(compass, Base.width/2 - compass.getWidth()/2, Base.height/2 -
compass.getHeight()/2, paint);                

      }

The scale() method reflects the tilt of the phone in the image. Similarly, the rotate() method points the image in the right direction (to the North). Finally the drawBitmap() method draws the image of the compass with the above conditions. Note the use of getWidth() in order to make placement of the image dynamic across different phones.

      public void onSizeChanged(int w, int h, int oldW, int oldH)

      {

            Base.width = w;

            Base.height = h;

      }

}

This ensures that the program uses the most up-to-date dimensions known and that it only reads the dimensions once as opposed to repeatedly updating the same dimensions.

Draw 2

public void onDraw(Canvas g)

{

      g.drawColor(Color.WHITE);

      g.scale((float)1.5, (float)1.5);

      paint.setColor(Color.BLACK);

      g.rotate(-1*Base.accelValues[0], 65, 65);

      g.drawText("X: " + String.format("%.4g%n", Base.accelValues[1]), Base.height/4-20, 55, paint);

      g.drawText("Y: " + String.format("%.4g%n", Base.accelValues[2]), Base.height/4-20, 65, paint);

      g.drawText("Z: " + String.format("%.4g%n", Base.accelValues[0]), Base.height/4-20, 75, paint);

}

Draw 3

public void onDraw(Canvas g)

{

      g.drawColor(Color.WHITE);

      g.scale((float)1.25, (float)1.25);

      paint.setColor(Color.BLACK);

      g.rotate(-1*Base.accelValues[0], 65, 65);

      g.drawText(Base.location.x+",", Base.height/4-20, 60, paint);

      g.drawText(Base.location.y+"", Base.height/4-20, 70, paint);

}

public class Base

{

      //[0] = z, [1] = x, [2] = y

      public static float[] accelValues = new float[3];

      public static Coordinate location = new Coordinate(0, 0);

      public static int width;

      public static int height;

}

static-based class that is accessed from all classes. The main Compass class updates the values from the sensors, and the three Draw classes read from it to get the values.

A screenshot of the emulator. Of course, no values are returned, so everything is at 0.