Android Compass App

/* V0.13
 *
 * 6/10/11 - 1725
 *
 */

package com.saltapps.compass;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.graphics.drawable.BitmapDrawable;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.util.Log;
import android.view.Display;
import android.view.WindowManager;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

public class Compass extends Activity implements SensorEventListener {

  static final String TAG = "Compass";

  SensorManager sensorManager;  // SensorManager lets you access the device's sensors
  Sensor sOrientation;          // needed for determining the sensor's orientation

  WindowManager mWindowManager; // The interface that apps use to talk to the window manager
  Display mDisplay;             // needed for getRotation, determining the handset's display orientation


  ImageView img;                                    // allows us to manipulate (rotate) the compass arrow
  TextView tvAzimuth, tvDirection, tvRotation;      // for displaying degrees, direction and screen rotation

  int vAzi, iRotation;  // degrees wrt mag north, screen rotation value

  Toast tstAcc;         // a toast message to indicate accuracy has changed


  @Override
  public void onCreate(Bundle savedInstanceState) { // carried out when activity launched
    super.onCreate(savedInstanceState);
    setContentView(R.layout.compass);   // lays the activity out according to the main.xml file in the res/layout folder

      sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);                     // get sensor service
      sOrientation = sensorManager.getDefaultSensor(Sensor.TYPE_ORIENTATION);               // sets sensor to orientation
      mWindowManager = (WindowManager) getSystemService(WINDOW_SERVICE);                    // get window service (for screen orientation purposes)
      mDisplay = ((WindowManager) getSystemService(WINDOW_SERVICE)).getDefaultDisplay();    // Returns default Display object

    tvAzimuth = (TextView) findViewById(R.id.tvAzimuth);        // for displaying degrees
    tvDirection = (TextView) findViewById(R.id.tvDirection);    // for displaying direction
    tvRotation = (TextView) findViewById(R.id.tvRotation);      // for displaying screen rotation

    img = (ImageView) findViewById(R.id.ivCompass);         // allows us to manipulate (rotate) the compass arrow

  } // onCreate


  @Override
  public void onResume() {  // actions to carry out upon returning to this activity
    super.onResume();
    sensorManager.registerListener(this, sOrientation, SensorManager.SENSOR_DELAY_NORMAL); // register to listen to sensors
  } // onResume


  @Override
  public void onPause() {   // actions to carry out when activity isn't in focus
    super.onPause();
    sensorManager.unregisterListener(this, sOrientation);  // unregister on pause to conserve battery power
  } // onPause




  public void onSensorChanged(SensorEvent event) {           // Listens to sensor and provides output

       /* event.values[0] : yaw, rotation around z axis - Azimuth
        * event.values[1] : pitch, rotation around x axis
        * event.values[2] : roll, rotation around y axis */


    iRotation = mDisplay.getRotation();

    switch(mDisplay.getRotation()) {    // determines angle to correct arrow by

        case 0: iRotation = 0;      // screen is in standard portrait mode, no rotation necessary
        break;
        case 1: iRotation = 90;     // screen rotated left from portrait, 90 degree rotation necessary
        break;
        case 2: iRotation = -180;   // screen upside down, 180 rotation necessary
        break;
        case 3: iRotation = -90;    // screen rotated right from portrait, -90 degree rotation necessary
        break;

    }   // switch

    tvRotation.setText("Screen Orientation: " + iRotation + "°");  // displays Orientation info

    vAzi = (int) event.values[0] + iRotation;   // changed from math.round, + iRotation to compensate for landscape mode. Makes camera view compass needle

    if (vAzi >= 360)        // 0 <= vAzi < 360
        vAzi -= 360;
    else if (vAzi < 0)
        vAzi += 360;

    if (vAzi < 22)
        tvDirection.setText("(N)");                 // determines which direction we're looking towards
     else if (vAzi >= 22 && vAzi < 67)
        tvDirection.setText("(NE)");
     else if (vAzi >= 67 && vAzi < 112)
        tvDirection.setText("(E)");
     else if (vAzi >= 112 && vAzi < 157)
        tvDirection.setText("(SE)");
     else if (vAzi >= 157 && vAzi < 202)
        tvDirection.setText("(S)");
     else if (vAzi >= 202 && vAzi < 247)
        tvDirection.setText("(SW)");
     else if (vAzi >= 247 && vAzi < 292)
        tvDirection.setText("(W)");
     else if (vAzi >= 292 && vAzi < 337)
        tvDirection.setText("(NW)");
     else if (vAzi >= 337)
        tvDirection.setText("(N)");
       else
          tvDirection.setText("Null");

    tvAzimuth.setText("Direction: " + vAzi +"°    ");  // outputs values to TextView


    drawArrow(vAzi);    // sends vAzi value to drawArrow method


  } // onSensorChanged


  public void drawArrow(int vAzi) { // draws arrow on screen, according to vAzi value


        img=(ImageView)findViewById(R.id.ivCompass);                    // sets our manipulatable image up using our compass imageView, which uses compass1.png
        Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.compass1); // encodes our png file as a bitmap, for manipulation using BitmapFactory

        int w = bmp.getWidth(); // Getting width & height of the given image
        int h = bmp.getHeight();

        Matrix mtx = new Matrix();
        mtx.postRotate(-vAzi);  // Setting post rotate angle according to the value obtained from handset's digital compass. Negative to rotate back towards North


        Bitmap rotatedBMP = Bitmap.createBitmap(bmp, 0, 0, w, h, mtx, true);        // Rotating Bitmap around  point we defined using half the .png file's width & height
        BitmapDrawable bmd = new BitmapDrawable(rotatedBMP);                        // sets Bitmap as drawable

        img.setImageDrawable(bmd);                                                  // finally, draws bitmap


  } // drawArrow



public void onAccuracyChanged(Sensor sensor, int accuracy) {

    if(sensor.getType()==Sensor.TYPE_ACCELEROMETER){
        Log.d(TAG, "Accuracy has changed: "+ accuracy); // logcats that acc has changed

        switch(accuracy) {                              // displays toast message when accuracy changes
        case 0: tstAcc.setText("Accuracy Unreliable");
                tstAcc.show();
        break;
        case 1: tstAcc.setText("Accuracy Low");
                tstAcc.show();
        break;
        case 2: tstAcc.setText("Accuracy Medium");
                tstAcc.show();
        break;
        case 3: tstAcc.setText("Accuracy High");
                tstAcc.show();
        break;
        }   // switch


    } // if


}   // onAccuracyChanged



}   // class