Android Sensor (Magnetic Field and Accelerometer sensor to create Compas)

Compas

Create new Android ProjectProject Name: Compas//tested from 2.3.3 to current android sdk
Build Target: Android 2.3.3 //or greater than thatApplication Name: CompasPackage Name: com.shaikhhamadali.blogspot.compasCreate activity file: Compas

1.code of activity:

package com.shaikhhamadali.blogspot.compass;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.view.View;

public class Compas extends Activity implements SensorEventListener {
 //declare Variables
 Float azimut;  
 CustomDrawableView mCustomDrawableView;// View to draw a compass
 //SensorManager lets you access the device's sensors
 private SensorManager mSensorManager;
 Sensor accelerometer;
 Sensor magnetometer;

 public class CustomDrawableView extends View {
  Paint paint = new Paint();
  public CustomDrawableView(Context context) {
   super(context);
   //color
   paint.setColor(0xff00ff00);
   //style 
   paint.setStyle(Style.STROKE);
   //stroke width
   paint.setStrokeWidth(2);
   //antiAlias
   paint.setAntiAlias(true);
   //text size
   paint.setTextSize(30);
  };

  protected void onDraw(Canvas canvas) {
   //declare Local Variables     
   int width = getWidth();
   int height = getHeight();
   int centerx = width/2;
   int centery = height/2;
   // Rotate the canvas with the azimut      
   if (azimut != null)
    //Preconcat the current matrix with the specified rotation.
    canvas.rotate(-azimut*360/(2*3.14159f), centerx, centery);
   //set color
   paint.setColor(0xff0000ff);
   //draw two lines
   canvas.drawLine(centerx, -1000, centerx, +1000, paint);
   canvas.drawLine(-1000, centery, 1000, centery, paint);
   //E,W,N,S directions
   canvas.drawText("N", centerx+15, centery-220, paint);
   canvas.drawText("S", centerx-30, centery+225, paint);
   canvas.drawText("E", centerx+215, centery-20, paint);
   canvas.drawText("W", centerx-220, centery+35, paint);
  }
 }



 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  mCustomDrawableView = new CustomDrawableView(this);
  setContentView(mCustomDrawableView);    
  //create instance of sensor manager and get system service to interact with Sensor

  mSensorManager = (SensorManager)getSystemService(SENSOR_SERVICE);
  accelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
  magnetometer = mSensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
 }

 protected void onResume() {
  super.onResume();
  // Register the sensor listeners
  mSensorManager.registerListener(this, accelerometer, SensorManager.SENSOR_DELAY_UI);
  mSensorManager.registerListener(this, magnetometer, SensorManager.SENSOR_DELAY_UI);
 }

 protected void onPause() {
  super.onPause();
  // unRegister the sensor listeners
  mSensorManager.unregisterListener(this);
 }

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

 float[] mGravity;
 float[] mGeomagnetic;
 public void onSensorChanged(SensorEvent event) {
  if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER)
   mGravity = event.values;
  if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD)
   mGeomagnetic = event.values;
  if (mGravity != null && mGeomagnetic != null) {
   float R[] = new float[9];
   float I[] = new float[9];
   /*Computes the inclination matrix I as well as the rotation matrix R transforming a vector from the device coordinate
    *  system to the world's coordinate system which is defined as a direct orthonormal basis*/
   boolean success = SensorManager.getRotationMatrix(R, I, mGravity, mGeomagnetic);
   if (success) {
    float orientation[] = new float[3];
    /*Computes the device's orientation based on the rotation matrix*/
    SensorManager.getOrientation(R, orientation);
    azimut = orientation[0]; // orientation contains: azimut, pitch and roll
   }
  }
  mCustomDrawableView.invalidate();
 }
}

3. note that:

• you can use TYPE_MAGNETIC and TYPE_ACCELEROMETER sensor to create compass and for anything  etc
• must unregister Sensor on pause and register on resume.
• Learn More About Barometer
• Learn more about Sensors and multiple types of sensors.
• Learn about how to get device Sensor List.
• Learn about use Of Type Accelerometer Sensor.
• Learn about use of Type Proximity Sensor.

4. conclusion:

• Some information about how to use TYPE_MAGNETIC and TYPE_ACCELEROMETER.
• know what are Sensors and how to use Sensors.

5. About the post:

• The code seems to explain itself due to comments, but if you have any questions you can freely ask too!

•  Don’t mind to write a comment whatever you like to ask, to know,to suggest or recommend.

•  Hope you enjoy it!

6. Source Code:

        you can download the source code GoogleDrive, Github

Cheers,

Hamad Ali Shaikh