Login Screen

                This program is for only for basic Login screen. It just consists of the Login page style how to create using Android studio.

Login Screen Xml Code : http://androidbyteja.blogspot.in/p/login-screen.html 

Android Studio

                     Android Studio is the official IDE for Android application development, based on IntelliJ IDEA. On top of the capabilities you expect from IntelliJ, Android Studio offers:

• Flexible Gradle-based build system

• Build variants and multiple apk file generation

• Code templates to help you build common app features

• Rich layout editor with support for drag and drop theme editing

• Lint tools to catch performance, usability, version compatibility, and other problems

• ProGuard and app-signing capabilities

• Built-in support for Google Cloud Platform, making it easy to integrate Google Cloud Messaging and App Engine

• And much more.

Download Android Studio.

Android Architecture

                                

Linux kernel

At the bottom of the layers is Linux. This provides basic system functionality like process management, memory management, device management like camera, keypad, display etc. Also, the kernel handles all the things that Linux is really good at such as networking and a vast array of device drivers, which take the pain out of interfacing to peripheral hardware.

 Libraries

On top of Linux kernel there is a set of libraries including open-source Web browser engine WebKit, well known library libc, SQLite database which is a useful repository for storage and sharing of application data, libraries to play and record audio and video, SSL libraries responsible for Internet security etc.

Android Runtime

This is the third section of the architecture. This section provides a key component called Dalvik Virtual Machine which is a kind of Java Virtual Machine specially designed and optimized for Android. The Dalvik VM makes use of Linux core features like memory management and multi-threading, which is intrinsic in the Java language. The Dalvik VM enables every Android application to run in its own process, with its own instance of the Dalvik virtual machine. The Android runtime also provides a set of core libraries which enable Android application developers to write Android applications using standard Java programming language.

Application Framework

The Application Framework layer provides many higher-level services to applications in the form of Java classes. Application developers are allowed to make use of these services in their applications.

Applications

You will find all the Android application at the top layer. You will write your application to be installed on this layer only. Examples of such applications are Contacts Books, Browser, Games etc.

Hello Teja Programme

Activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.helloworld.MainActivity" >

    <TextView
        android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_centerHorizontal="true"
 android:layout_centerVertical="true"
 android:text="@string/hello_Teja"
 tools:context=".MainActivity"/>

</RelativeLayout>

MainActivity.java

package com.example.helloworld;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;


public class MainActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

AndroidManifest.xml

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

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

    package="com.example.helloworld"

    android:versionCode="1"

    android:versionName="1.0" >

    <uses-sdk

        android:minSdkVersion="8"

        android:targetSdkVersion="21" />

    <application

        android:allowBackup="true"

        android:icon="@drawable/ic_launcher"

        android:label="@string/app_name"

        android:theme="@style/AppTheme" >

        <activity

            android:name=".MainActivity"

            android:label="@string/app_name" >

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

    </application>

</manifest>

Before Creating A New Application the basic things to be known !

              When you create android application the following folders are created in the package explorer in eclipse which are as follows:

src: Contains the .java source files for your project. You write the code for your application in this file. This file is available under the package name for your project.

gen —This folder contains the R.java file. It is compiler-generated file that references all the resources found in your project. You should not modify this file.

Android 4.0 library: This folder contains android.jar file, which contains all the class libraries needed for an Android application.

assets: This folder contains all the information about HTML file, text files, databases, etc.

bin: It contains the .apk file (Android Package Key) that is generated by the ADT during the build process. An .apk file is the application binary file. It contains everything needed to run an Android application.

res: This folder contains all the resource file that is used by android application. It contains sub-folders as: drawable, menu, layout, and values etc.

AndroidManifest.xmlfile in detail.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.teja" android:versionCode="1" android:versionName="1.0">
<uses-sdk android:minSdkVersion="8" android:targetSdkVersion="18" />
<application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme">
<activity android:name="com.example.teja.MainActivity" android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>

• It contains the package name of the application.

• The version code of the application is 1.This value is used to identify the version number of your application.

• The version name of the application is 1.0

• The android:minSdkVersion attribute of the element defines the minimum version of the OS on which the application will run.

• ic_launcher.png is the default image that located in the drawable folders.

• app_name defines the name of applicationand available in the strings.xml file.

• It also contains the information about the activity. Its name is same as the application name.

     Android Activities :

                Activity provides the user interface. When you create an android application in eclipse through the wizard it asks you the name of the activity. Default name is MainActivity. You can provide any name according to the need. Basically it is a class (MainActivity) that is inherited automatically from Activity class. Mostly, applications have oneor more activities; and the main purpose of an activity is to interact with the user. Activity goes through a number of stages, known as an activity’s life cycle.

                  An activity is implemented as a subclass of Activity class as follows: 

        public class MainActivity extends Activity {

                      } 

 Services :

                    A service is a component that runs in the background to perform long-running operations.    For example, a service might play music in the background while the user is in a different application, or it might fetch data over the network without blocking user interaction with an activity. A service is implemented as a subclass of Service class as follows:

public class MyService extends Service {

                                                               }

Broadcast Receivers:

                   Broadcast Receivers simply respond to broadcast messages from other applications or from the system. For example, applications can also initiate broadcasts to let other applications know that some data has been downloaded to the device and is available for them to use, so this is broadcast receiver who will intercept this communication and will initiate appropriate action. A broadcast receiver is implemented as a subclass of BroadcastReceiver class and each message is broadcasted as an Intent object.

              public class MyReceiver extends BroadcastReceiver {

                                         }

Content Providers:

                   A content provider component supplies data from one application to others on request. Such requests are handled by the methods of the ContentResolver class. The data may be stored in the file system, the database or somewhere else entirely. A content provider is implemented as a subclass of ContentProvider class and must implement a standard set of APIs that enable other applications to perform transactions.

public class MyContentProvider extends ContentProvider {

                                             } 

Android

           

            Android is a mobile operating system (OS) based on the Linux kernel and currently developed by Google. With a user interface based on direct manipulation, Android is designed primarily for touchscreen mobile devices such as smartphones and tablet computers, with specialized user interfaces for televisions (Android TV), cars (Android Auto), and wrist watches (Android Wear).

The OS uses touch inputs that loosely correspond to real-world actions, like swiping, tapping, pinching, and reverse pinching to manipulate on-screen objects, and a virtual keyboard. Despite being primarily designed for touchscreen input, it also has been used in game consoles, digital cameras, regular PCs (e.g. the HP Slate 21) and other electronics.

What is Android?

                      It is an open-sourced operating system that is used primarily on mobile devices, such as cell phones and tablets. It is a Linux kernel-based system that’s been equipped with rich components that allows developers to create and run apps that can perform both basic and advanced functions.

                 Android versions have been developed under a confectionery-themed code name and released in alphabetical order; the exceptions are versions 1.0 and 1.1, as they were not released under specific code names:

                  

                        Alpha (1.0) - Beta (1.1) - Cupcake (1.5) - Donut (1.6) - Eclair (2.0–2.1) - Froyo (2.2–2.2.3) - Gingerbread (2.3–2.3.7) - Honeycomb (3.0–3.2.6) - Ice Cream Sandwich (4.0–4.0.4) - Jelly Bean (4.1–4.3.1) - KitKat (4.4–4.4.4) - Lollipop (5.0–5.0.2)

             Android apps are written in the Java programming language. The Android SDK tools compile your code—along with any data and resource files—into an APK: an Android package, which is an archive file with an .apk suffix. One APK file contains all the contents of an Android app and is the file that Android-powered devices use to install the app.

 Following is the list of software's you will need before you start your Android application programming.

• Java JDK5 or JDK6
• Android SDK
• Eclipse IDE for Java Developers (optional)
• Android Development Tools (ADT) Eclipse Plugin (optional)

Before you start writing your first example using Android SDK, you have to make sure that you have setup your Android development environment.