Before going to Tell what is an Android I Want to tell you what is an OS??
OS stands for Operating System which means an software to interface between hardware and software.For Ex Windows Xp ,Windows 7, Windows 8, Ubuntu , Fedora , Mint , Chromium , Debain , IOS , Symbian, Bada OS etc. There are more than hundreds of OS available in the market. Some of which are opensource and some of which are closed source.

Now you will be wondering what is an open-source and closed-source.
Let's than discuss here.
Open source is generally free to use, free to edit and  free to publish. If you have little bit of programming knowledge than you can also learn and modify it. They are published under general public license(GPL).
For example there are many open source OS available Like Ubuntu,Mint etc. all designed on Linux Kernel.

What is than Linux kernel?

Kernel is nothing but an application or software at the lowest level communicating with your hardware. It is also responsible for all the process running on the user mode also for whatever commands user is giving over the GUI(Graphical Interface User). Linux is nothing but an family of Unix type Operating System which is evolved in very earlier ages.

What is Android?

Android is an operating system based on Linux with a Java Programming interface, targeted at mobile hardware such as phones and tablet computers. Android is powerful tool which give an Enormous power to customize your own mobile in your own way.
Why Android?

Today Android powers hundreds of millions of mobile devices in more than 190 countries around the globe. It's the largest installed base of any mobile platform and its growing fast—every day another million users power up their Android devices for the first time and start looking for exciting apps, games, and other digital content. Android has now became the world's most popular mobile platform. With Android we can use all the Google apps we know and use, plus there are more than 600,000 apps and games available on Google Play to keep us entertained, alongside millions of songs and books, and thousands of movies.

What for you?

As Developer android provide you all the stuff you need like a compiler, debugger and a device emulator as well as its own Java Virtual machine.

Its Just A Beginning. Let see How Far I can reach.

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Today Sensor are becoming very prominent in Android Smart phones. Without them an any app look dull and ineffective. Today sensors plays a vital role in android smartphones. Today sensor are used in Application like Gaming, Educational etc. So managing the Sensor has become the most important. So here we are, Android itself supports several types of sensors via the library SensorManager, for example the accelerometer, gyroscope etc. Since Testing your an Android App as developer with an emulator is worthless since it does not support any particular sensor hardware. So we need an real device to test it. Now let’s go little bit technically in the topic how to create and manage your first app with sensors.

So we can access a SensorManager via getSystemService(SENSOR_SERVICE) which an by default code which we will be needing to write. The Sensor class defines several constants for accessing the different types of sensors like:

	TYPE_ACCELEROMETER	describing an accelerometer sensor type.
	TYPE_AMBIENT_TEMPERATURE	describing an ambient temperature sensor type
	TYPE_GRAVITY	describing a gravity sensor type.
	TYPE_GYROSCOPE	describing a gyroscope sensor type
	TYPE_LIGHT	describing a light sensor type.
	TYPE_LINEAR_ACCELERATION	describing a linear acceleration sensor type.
	TYPE_MAGNETIC_FIELD	describing a magnetic field sensor type.
	TYPE_ORIENTATION	describing a orientation sensor type.
	TYPE_PRESSURE	describing a pressure sensor type
	TYPE_PROXIMITY	describing a proximity sensor type.
	TYPE_RELATIVE_HUMIDITY	describing a relative humidity sensor type.
	TYPE_ROTATION_VECTOR	describing a rotation vector sensor type.
	TYPE_TEMPERATURE	describing a temperature sensor type.

We will be discussing about each type of sensor in detail. Just for time being you  just memorize them.

We can access different types of Sensor via the  sensorManager.getDefaultSensor () method, which takes the type of sensor requested and then returns the default sensor matching it. If we need to access the raw sensors we have to use getSensorList.

One more thing for starting any service like we are invoking an Sensor Activity then we have to register that activity with that particular device which can be done with SensorEventListener by registering an object on it. This listener will get informed, if the sensor data changes.

Since during invoke of an Sensor Activity lot of battery is required which will be using if an activity is idle which can cause to degrade your battery life. So to avoid

 An unnecessary usage of battery we have to register our listener in the onResume() method and de-register it in theonPause() method. These are the part of activity-life cycle which we don’t have bother about. I will be discussing it in my further articles. 

Here basically I will be going to discuss mainly about Accelerometer.So now let see how to make it. Here are some snaps for each steps which will be helpful for you to make your application. 

I think you  are familiar about how to install configure an android environment in your pc.If not I will be posting it soon then. So just start an eclipse go to file à new à android project.Give the required project name, package name etc. Than go to src folder open your main .java file to edit the code.

Also open the main.xml file from res à layout àmain.xml

Make the following Change in your layout main.xml as given below

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical" >

    <TextView

        android:id="@+id/textView"

        android:layout_width="match_parent"

        android:layout_height="match_parent"

        android:text="Shake to change color and to get toast" />

</LinearLayout>

This layout file is to display the first screen to be visible when user logins.

Change the code in your  Activity to the following.

package sensor.accelero;

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.Toast;

These are the libraries which will be used while developing our simple app.I will explain each of it one by one.

Android.app.activity à

The Activity class is an important part of an application's overall lifecycle, and the way activities are launched and put together is a fundamental part of the platform's application model.

Activity Lifecycle

Activities in the system are managed as an activity stack. When a new activity is started, it is placed on the top of the stack and becomes the running activity -- the previous activity always remains below it in the stack, and will not come to the foreground again until the new activity exits.
The following diagram shows the important state paths of an Activity. The square rectangles represent callback methods we can implement to perform operations when the Activity moves between states. The colored ovals are major states the Activity can be in.

android.graphics.Color à

   The Color class defines methods for creating and converting color ints. Colors are represented as packed ints, made up of 4 bytes: alpha, red, green, blue. The values are unpremultiplied, meaning any transparency is stored solely in the alpha component, and not in the color components.

android.hardware.Sensor à Class representing a sensor which I have described above.

android.hardware.SensorEventListener à

This class represents a Sensor event and holds informations such as the sensor's type, the time-stamp, accuracy and of course the sensor's data.

Definition of the coordinate system used by the SensorEvent API.

The coordinate-system is defined relative to the screen of the phone in its default orientation.

 

axes are not swapped when the device's screen orientation changes.

The X axis is horizontal and points to the right, the Y axis is vertical and points up and the Z axis points towards the outside of the front face of the screen. In this system, coordinates behind the screen have negative Z values.

This coordinate system is different from the one used in the Android 2D APIs where the origin is in the top-left corner.

android.hardware.SensorManager à

SensorManager lets us access the device's sensors. To get  an instance of this class by calling Context.getSystemService() with the argument SENSOR_SERVICE.
Also we have to care that we should switch off the sensors when they are not used, failing so it will drain our battry and also reduce the battery life.

I think you are familiar with these libraries

android.os.Bundle à A mapping from String values to various Parcelable types.

android.view.View  à Visual indicator of progress in some operation. For ex TextView, SurfaceView

android.widget.Toast à When the view is shown to the user, appears as a floating view over the application. The idea is to be as unobtrusive as possible, while still showing the user the information you want them to see.


android.view.Window à
This is an abstract base class for a top-level window look and behaviors. An instance of this class must be used as the top-level view added to the window manager. It provides standard UI facilities such as a background, title area, default key processing, etc.


android.view.WindowManager. à

The interface that apps use to talk to the window manager.To use this we have to use Context.getSystemService(Context.WINDOW_SERVICE) to get one of these.

Now in class Main write the following code

     public class Main extends Activity implements SensorEventListener {

//Here extends and implements means inheritance. Here class Main is Inheriting the features of class activity and SensorEventListener.

  private SensorManager sensorManager;

// This is creating an instance of SensorManager.

// Note: It is Case sensitive. So be careful with that.

 

private boolean color = false;

/*** Creating a Boolean variable. Boolean is a variable which accepts two variable true or false. Initially I am giving it as false. Means no color is set initially. ***/

  private View view;

// This is creating an view.

  private long lastUpdate;

/*** This is the update variable which checks for the update.If update is less than 200ms than it will automatically change the background color.***/

 

/** Called when the activity is first created. I think  */

  @Override

  public void onCreate(Bundle savedInstanceState) {

    requestWindowFeature(Window.FEATURE_NO_TITLE);

/*** This line will remove the The Action Bar from the activity screen which we generally see with the title of the app.***/

    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,

        WindowManager.LayoutParams.FLAG_FULLSCREEN);

/*** getWindow() will reterive the initial window screen.It do so by taking flag values. The flag values set will set the initial flag to layout of the screen to the full screen. It is the notification that screen is set to FULL_SCREEN mode***/

    super.onCreate(savedInstanceState);

    setContentView(R.layout.main);

    view = findViewById(R.id.textView);

/*** This is getting an default UI id of an textview defined in the main.xml***/

    view.setBackgroundColor(Color.BLUE);

/***Setting up the Background to Blue initially when activity is started.***/

    sensorManager = (SensorManager)getSystemService(SENSOR_SERVICE);

/*** This is getting a System Service through getSystemService()

As I discussed above.***/

    lastUpdate = System.currentTimeMillis();

/*** lastUpdate variable is set to current system time using System.currentTimeMillis(); ***/

  }

  @Override

  public void onSensorChanged(SensorEvent event)

// TODO AUTO-GENERATED CLASS

/*** They is the Auto generated class. When you implement the sensoreventlistener class it will auto generate some by default functions***/

 {

    if(event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {

      getAccelerometer(event);

/** This is checking if the sensor which the app get is TYPE_ACCELEROMETER or not. ***/

    }

  }

  private void getAccelerometer(SensorEvent event) {

    float[] values = event.values;

    /* Movement of the phone in x ,y, z direction is stored in values of given event in form of arrays.***/

    float x = values[0];

    float y = values[1];

    float z = values[2];

    float accelationSquareRoot = (x * x + y * y + z * z)

        / (SensorManager.GRAVITY_EARTH * SensorManager.GRAVITY_EARTH);

    long actualTime = System.currentTimeMillis();

// Storing the actual time.

    if (accelationSquareRoot >= 1)

/***checking if that value is greater than 1 or not  ***//

    {

      if (actualTime - lastUpdate < 100) {

        return;

      }

      lastUpdate = actualTime;

      Toast.makeText(this, "Device was shaked", Toast.LENGTH_LONG)

          .show();

// Toast is made when device is shaken

/*** And color is changed. Accordingly. We can also Define other Activity in it.***/

      if (color) {

        view.setBackgroundColor(Color.CYAN);

      } else {

        view.setBackgroundColor(Color.RED);

      }

      color = !color;

    }

  }

  @Override

  public void onAccuracyChanged(Sensor sensor, int accuracy) {

  }

  @Override

  protected void onResume() {

    super.onResume();

    // registering this class as a listener for the orientation and

    // accelerometer sensors

    sensorManager.registerListener(this,

        sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),

        SensorManager.SENSOR_DELAY_NORMAL);

// Giving some delay to register.

  }

  @Override

  protected void onPause() {

    // unregister listener

    super.onPause();

    sensorManager.unregisterListener(this);

/*** this à it is showing in which reference you are going to unregister your sensor.***/

  }

}

/*** It’s the unregistering of the service so as to save battery life.

Final Output screen
 When you Run this application.

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You all be wondering why andronomous? Is there a better name than that. Here i have take this name with zeal to provide a platform to the newbeeis as to me to think,create,innovate and mold there ideas in One place. Andronomous is derieved from two words Android and Autonomous which means you are acting independently or having a freedom to do something. So this is the place where we can learn, create and develop new ideas independently and having full freedom to ask whatever you came across of.

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