Using orientation sensors: simple compass sample

In this post we will show how to get the sensor informatió N of the device to do a simple compass application.

Getting the magnetic orientation with the type_orientation sensor is deprecated, And now you must subscribe to type_accelerometer and type_magnetic_field to get the correct orientation. this way is a little tricky, but with this sample you will get it very
Easy.

This is the code for an activity that shows in a canvas a simple compass:

package com.samplecompass;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 CompassActivity extends Activity implements SensorEventListener {   Float azimut;  // View to draw a compass   public class CustomDrawableView extends View {    Paint paint = new Paint();    public CustomDrawableView(Context context) {      super(context);      paint.setColor(0xff00ff00);      paint.setStyle(Style.STROKE);      paint.setStrokeWidth(2);      paint.setAntiAlias(true);    };     protected void onDraw(Canvas canvas) {      int width = getWidth();      int height = getHeight();      int centerx = width/2;      int centery = height/2;      canvas.drawLine(centerx, 0, centerx, height, paint);      canvas.drawLine(0, centery, width, centery, paint);      // Rotate the canvas with the azimut           if (azimut != null)        canvas.rotate(-azimut*360/(2*3.14159f), centerx, centery);      paint.setColor(0xff0000ff);      canvas.drawLine(centerx, -1000, centerx, +1000, paint);      canvas.drawLine(-1000, centery, 1000, centery, paint);      canvas.drawText("N", centerx+5, centery-10, paint);      canvas.drawText("S", centerx-10, centery+15, paint);      paint.setColor(0xff00ff00);    }  }   CustomDrawableView mCustomDrawableView;  private SensorManager mSensorManager;  Sensor accelerometer;  Sensor magnetometer;   protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    mCustomDrawableView = new CustomDrawableView(this);    setContentView(mCustomDrawableView);    // Register the sensor listeners    mSensorManager = (SensorManager)getSystemService(SENSOR_SERVICE);      accelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);    magnetometer = mSensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);  }   protected void onResume() {    super.onResume();    mSensorManager.registerListener(this, accelerometer, SensorManager.SENSOR_DELAY_UI);    mSensorManager.registerListener(this, magnetometer, SensorManager.SENSOR_DELAY_UI);  }   protected void onPause() {    super.onPause();    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];      boolean success = SensorManager.getRotationMatrix(R, I, mGravity, mGeomagnetic);      if (success) {        float orientation[] = new float[3];        SensorManager.getOrientation(R, orientation);        azimut = orientation[0]; // orientation contains: azimut, pitch and roll      }    }    mCustomDrawableView.invalidate();  }}