Running Android virtual device - App Development Tutorial

Running Your App on Android virtual device

If you followed the previous tutorial Building your own Android App to create an Android project, you have created your first Hello World Android application source files that allow you to immediately run the app on the Android virtual device.

How you run your app depends on two things:

 Whether you have a real Android-powered device and whether you’re using Eclipse. This tutorial shows you how to install and run your app on a real device and on the Android emulator (Android virtual device), and in both cases with either Eclipse or the command line tools.

Before you run your app, note the various files that make up an Android project in the Package Explorer in Eclipse. 

Android project architecture 

android project architecture

The various folders and their files are as follows:

AndroidManifest.xml

The manifest file describes the fundamental characteristics of the app and defines each of its components.

For example all Activities and Services of the application must be declared in this file. It must also contain the required permissions for the application. For example if the application requires network access it must be specified.

src/

Directory for your app's main source files. By default, it includes an Activity class that runs when your app is launched using the app icon.

res/

Contains several sub-directories for app resources. res directory contains structured values which are known to the Android platform, the assets directory can be used to store any kind of data. You access this data via the AssetsManager which you can access the getAssets() method. AssetsManager allows to read an assets as InputStream with the open() method. 

drawable-hdpi/

Directory for drawable objects (such as bitmaps) that are designed for high-density (hdpi) screens. Other drawable directories contain assets designed for other screen densities.

layout/

Directory for files that define your app's user interface.

values/

Directory for other various XML files that contain a collection of resources, such as string and color definitions.

When you build and run the default Android app, the default Activity class starts and loads a layout file that says "Hello World." The result is nothing exciting, but it's important that you understand how to run your app before you start developing.

Run on the Android virtual device (Emulator)

You are now ready to test your application on the Android emulator. Right-click the project name in Eclipse and select Run As  ->  Android Application .

Run on the Android virtual device (Emulator)

If you have not made any mistakes in the project, you should now be able to see the application installed and running on the Android virtual device (emulator).

Run on a Real Android Device

If you have a real Android-powered device, here's how you can install and run your app . Visit this link from Google to know how to   Run on a Real Android Device

http://developer.android.com/training/basics/firstapp/running-app.html

Now you can explore some resources and book for increase your knowledge , you can begin with beginner book : Beginning Android 4 Application Development book reviews

Create an Android Project & import samples with Eclipse

Building your own Android App

Welcome to Android Development Tutorial!

This Tutorial teaches you how to build your own (first) Android app. You’ll learn how to create an Android project and how to import the Android app’s project into Eclipse.

Before you start this Tutorial, be sure you have your android development environment set up.

 You need to:

- Download the Android SDK.

- Install the ADT plugin for Eclipse (if you’ll use the Eclipse IDE (.

- Download the latest SDK tools and platforms using the SDK Manager.

We discuss these steps in previous tutorial Android SDK tools and Installing Android ADT Plugin For Eclipse, once you've finished the setup; you're ready to begin this tutorial.

This tutorial teaches you some fundamental concepts about Android development, so it's important that you follow each step.

Creating Your First Android Application

You’ve downloaded the SDK, installed Eclipse, and plugged in the plug-in. You are now ready to start programming for Android. Start by creating a new Android project and setting up your Eclipse run and debug configurations, as described in the following steps.

Creating a New Android Project

To create a new Android project using the Android New Project Wizard, do the following:

- Select File -> New -> Project.

- Select the Android Project application type from the Android folder, and click next.

- In the wizard that appears, enter the details for your new project. On the first page, the Project Name is the name of your project file. You can also select the location your project should be saved.

The next step lets you select the build target for your application. The build target is the version of the Android framework SDK that you plan to develop with. In addition to the open sourced Android SDK libraries available as part of each platform release, Google offers a set of proprietary APIs that offer additional libraries (such as Maps). If you want to use these Google-specific APIs, you must select the Google APIs package corresponding to the platform release you want to target.

The final step allows you to specify the application properties. The Application Name is the friendly name for your application; the Package Name specifies its Java package; the Create Activity option lets you specify the name of a class that will be your initial Activity; and setting the Minimum SDK lets you specify the minimum version of the SDK that your application will run on.

Creating a New Android Project

Creating a New Android Project

Creating a New Android Project

Creating a New Android Project

    

More details about android PROPERTIES

Project Name: Provide any name of your choice here; I named it ‘Hello World’.

Build Target: This field asks you which version of Android do you want your App to target on. Check any one of your choice. Along with Target Name you can see the API Level (marked in the box) which is numbers representing the level of the Android API. This would be used to specify Min SDK Version field, which we’ll know in few seconds.

Application Name: This is a name which you’d want to give to your final Application. This would be displayed in the phone’s menu and also on title bar of App. You may provide any name of your choice. It's not a mandatory field.

Package Name: This gives a package structure to your App. If you are familiar to java you probably already related it to java package, which is absolutely correct. You may name it anything like ‘android.firstApp’ or ‘com.apps.android.firstApp’. The dots in the package name just provide a hierarchical structure to app.  The package name must have at least two identifiers (dot separated). It's a required field.

Create Activity: We discuss Activities in this tutorial Android Application User Interface tutoril  , but for now I'd like you to know that every App’s function is treated as an activity in android, and you can give a name to your activity. You can have activities and sub-activities in your apps. Again, this is not a mandatory field. Note: It won't allow spaces in this field.

Min SDK Version: Do you remember, we came across this name while talking about ‘Build Target’. This field tells your app to put an extra check on the application that it is only focused on some minimum level of Build Target. This field takes in numeric value corresponding to the API Level of Build target. It would specify that if any target environment is below this Min SDK Version, then this application won't work. This ideally should be equal to the API Level value of the Build Target selected above by you. But this is not a Mandatory field, and so even if you give any other version, it would accept it with a warning message.

The Summary of android PROPERTIES

Project name: The name of the project

Application name: A user-friendly name for your application

Package name: The name of the package. You should use a reverse domain name for this.

Create Activity: The name of the first activity in your application

Min SDK Version: The minimum version of the SDK that your project is targeting

Import the app’s Android project into Eclipse

-  Opening  the Import  Dialog then  Select  File ->  Import…  to  open  the  Import  dialog

- Importing your app’s project (sample code).  In the Import dialog, expand the General node and select Existing Projects into Workspace, then click Next -> to proceed to the Import Projects step. Ensure that Select root directory is selected, and then click the Browse button. In the Browse for Folder dialog, locate the sample folder, select it and click OK. Click Finish to import the project into Eclipse. The project now appears in the Package Explorer window at the left side of the Eclipse window.

Import the app’s Android project into Eclipse

Import the app’s Android project into Eclipse

  

Voice Search arrives in 13 new languages

“Norwegian restaurants in New York City.” I can type that phrase fast, but I can say it even faster—and when I’m on the go, speed is what I’m looking for. With Voice Search, you can speak into your phone to get search results quickly and easily. Voice Search is already available in 29 languages, and today, we're bringing support to 13 new languages for Android users—bringing the total to 42 languages and accents in 46 countries. In fact, 100 million new speakers can use Voice Search now, with the addition of:

Basque Bulgarian Catalan European Portuguese Finnish Galician Hungarian

Icelandic Norwegian Romanian Serbian Slovak Swedish

Each new language usually requires that we initially collect hundreds of thousands of utterances from volunteers and, although we’ve been working on speech recognition for several years, adding these new languages led our engineers and scientists to tackle some unique challenges. While languages like Romanian follow predictable pronunciation rules, others, like Swedish, required that we recruit native speakers to provide us with the pronunciations for thousands of words. Our scientists then built a machine learning system based on that data to predict how all other Swedish words would be pronounced.

This update has already started to roll out, and will continue to do so over the course of the next week. How you get started with Google Voice Search depends on what kind of phone you have. If your phone runs Android 2.2 or later, and you see the microphone icon on the Google Search widget on your homescreen, all you have to do is tap the icon to start a voice-powered search. Otherwise, you can install the Voice Search app from Google Play. Note that you can only speak one language into the app at a time, and you may need to change your language settings to use one of these new languages.

As with other languages we’ve added, one of the major benefits to Google’s cloud-based model is that the more people use Voice Search, the more accurate it becomes.

Posted by Bertrand Damiba, Product Manager

Creating Your Own Spelling Checker Service

Posted by Satoshi Kataoka and Ken Wakasa of the Android text input engineering team

The Spelling Checker framework improves the text-input experience on Android by helping the user quickly identify and correct spelling errors. When an app uses the spelling checker framework, the user can see a red underline beneath misspelled or unrecognized words so that the user can correct mistakes instantly by choosing a suggestion from a dropdown list.



If you are an input method editor (IME) developer, the Spelling Checker framework gives you a great way to provide an even better experience for your users. You can add your own spelling checker service to your IME to provide consistent spelling error corrections from your own custom dictionary. Your spelling checker can recognize and suggest corrections for the vocabularies that are most important to your users, and if your language is not supported by the built-in spelling checker, you can provide a spelling checker for that language.



The Spelling Checker APIs let you create your own spelling checker service with minimal steps. The framework manages the interaction between your spelling checker service and a text input field. In this post we’ll give you an overview of how to implement a spelling checker service. For details, take a look at the Spelling Checker Framework API Guide.

1. Create a spelling checker service class

To create a spelling checker service, the first step is to create a spelling checker service class that extends android.service.textservice.SpellCheckerService.



For a working example of a spelling checker, you may want to take a look at the SampleSpellCheckerService class in the SpellChecker sample app, available from the Samples download package in the Android SDK.

2. Implement the required methods

Next, in your subclass of SpellCheckerService, implement the methods createSession() and onGetSuggestions(), as shown in the following code snippet:

@Override                                                                        
public Session createSession() {                                             
    return new AndroidSpellCheckerSession();                                 
}       

private static class AndroidSpellCheckerSession extends Session {            
    @Override                                                                
    public SuggestionsInfo onGetSuggestions(TextInfo textInfo, int suggestionsLimit) {
        SuggestionsInfo suggestionsInfo;
        ... // look up suggestions for TextInfo
        return suggestionsInfo;
    }      
}

Note that the input argument textInfo of onGetSuggestions(TextInfo, int) contains a single word. The method returns suggestions for that word as a SuggestionsInfo object. The implementation of this method can access your custom dictionary and any utility classes for extracting and ranking suggestions.



For sentence-level checking, you can also implement onGetSuggestionsMultiple(), which accepts an array of TextInfo.

3. Register the spelling checker service in AndroidManifest.xml

In addition to implementing your subclass, you need to declare the spelling checker service in your manifest file. The declaration specifies the application, the service, and a metadata file that defines the Activity to use for controlling settings. Here’s an example:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.android.samplespellcheckerservice">
    <application android:label="@string/app_name">
        <service 
            android:label="@string/app_name"    
            android:name=".SampleSpellCheckerService" 
            android:permission="android.permission.BIND_TEXT_SERVICE">
            <intent-filter>
                <action 
                    android:name="android.service.textservice.SpellCheckerService" />
            </intent-filter>
            <meta-data
                android:name="android.view.textservice.scs"
                android:resource="@xml/spellchecker" />
        </service>
    </application>
</manifest>

Notice that the service must request the permission android.permission.BIND_TEXT_SERVICE to ensure that only the system binds to the service.

4. Create a metadata XML resource file

Last, create a metadata file for your spelling checker to define the Activity to use for controlling spelling checker settings. The metadata file can also define subtypes for the spelling checker. Place the file in the location specified in the

element of the spelling checker declaration in the manifest file.



In the example below, the metadata file spellchecker.xml specifies the settings Activity as SpellCheckerSettingsActivity and includes subtypes to define the locales that the spelling checker can handle.

<spell-checker xmlns:android="http://schemas.android.com/apk/res/android"
    android:label="@string/spellchecker_name"
    android:settingsactivity="com.example.SpellCheckerSettingsActivity" />
    <subtype   
        android:label="@string/subtype_generic" 
        android:subtypeLocale="en" />
</spell-checker>

That’s it! Your spelling checker service is now available to client applications such as your IME.

Bonus points: Add batch processing of multiple sentences

For faster, more accurate spell-checking, Android 4.1 (Jelly Bean) introduces APIs that let clients pass multiple sentences to your spelling checker at once.



To support sentence-level checking for multiple sentences in a single call, just override and implement the method onGetSentenceSuggestionsMultiple(), as shown below.

private static class AndroidSpellCheckerSession extends Session {                 
    @Override                                                                
    public SentenceSuggestionsInfo[] onGetSentenceSuggestionsMultiple(
          TextInfo[] textInfo, int suggestionsLimit) {
        SentenceSuggestionsInfo[] sentenceSuggestionsInfos;
        ... // look up suggestions for each TextInfo
        return sentenceSuggestionsInfos
    }      
}

In this case, textInfo is an array of TextInfo, each of which holds a sentence. The method returns lengths and offsets of suggestions for each sentence as a SentenceSuggestionsInfo object.

Documents and samples

If you’d like to learn more about how to use the spelling checker APIs, take a look at these documents and samples:

• Spelling Checker Framework API Guide — a developer guide covering the Spelling Checker API for clients and services.


• SampleSpellCheckerService sample app — helps you get started with your spelling checker service.
  
  
  • You can find the app at /samples/android-15/SpellChecker/SampleSpellCheckerService in the Samples download.
  
  


• HelloSpellChecker sample app — a basic app that uses a spelling checker.
  
  
  • You can find the app at /samples/android-15/SpellChecker/HelloSpellChecker in the Samples download.
  
  

To learn how to download sample apps for the Android SDK, see Samples.

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Download And Installing Android ADT Plugin For Eclipse

Download And Installing Android ADT Plugin For Eclipse

Previous tutorial  Android SDK tools show you how to install android SDK tools and the Eclips IDE . Now I'm going to complete the steps. First I will show you how to download and install Android ADT Plugin For Eclipse, then how to update the Android ADT Plugin For Eclipse , and finally how to create avd .

Installing the ADT Plugin for Eclipse

Android Development Tools (ADT)

When Eclipse is launched, select Help ->  Install New Software  to install the Android Development Tools (ADT) plug-in for Eclipse.

ADT Plugin for Eclipse   

In the Install dialog that appears, specify https://dl-ssl.google.com/android/eclipse/ and press Enter. After a while, you will see the Developer Tools' item appear in the middle of the window . Expand it to reveal its content: Android DDMS, Android Development Tools, Android Hierarchy Viewer, and Android Traceview. 

Check all of them and click Next twice.

Installing the ADT Plugin

You will be asked to review and accept the  licenses. Check the “I accept the terms of the  license agreements” option and click Finish. Once the installation is completed, you will be asked to  restart Eclipse. Go ahead and restart Eclipse now. 

Installing the ADT Plugin

When Eclipse is restarted, you are asked to configure your Android SDK. As the  Android SDK has already been downloaded earlier In the previous tutorial Android SDK tools , check the “Use existing  SDKs” option and specify the directory where you  have installed the Android SDK. Click Next. 

After this step, you are asked to send your usage statistics to Google. Once you have selected your  choice, click Finish.

For more details about installing the ADT Plugin, go to

And carefully follow developer.android.com/sdk/eclipse-adt.html

the instructions for downloading and installing the ADT Plugin. 

If you have any problems downloading the ADT, check out Google’s help at

http://developer.android.com/sdk/eclipse-adt.html#installing

Updating the ADT Plugin for Eclipse

In most cases, you can update your ADT plug-in simply as follows:

1.   Navigate to Help -> Check for Updates.

2.   If there are any ADT updates available, they will be presented. Simply select them and choose Install.

Sometimes a plug-in upgrade may be so significant that the dynamic update mechanism can’t be used. In those cases you may have to remove the previous plug-in  completely before installing the newer version.

Updating the ADT Plugin for Eclipse  

Updating the ADT Plugin for Eclipse  

Updating the ADT Plugin for Eclipse  

Updating the ADT Plugin for Eclipse  

Updating the ADT Plugin for Eclipse  

Updating the ADT Plugin for Eclipse  

      

Creating Android Virtual Devices (AVDs) for Use in the Android Emulator

Creating Android Virtual Devices (AVDs)

The Android emulator, included in the Android SDK, allows you to run Android apps in a simulated environment on your computer rather than on an actual Android device. Before running an app in the emulator, you must create an Android Virtual Device (AVD) which defines the characteristics of the device on which you want to test, including the screen size in pixels, the pixel density, the physical size of the screen, size of the SD card for data storage and more. If you want to test your apps for multiple Android devices, you can create separate AVDs that emulate each unique device. To do so, perform the following steps:

To create an AVD, From Eclipse select Window ->  AVD Manager to display the Android Virtual Device Manager window .

Creating Android Virtual Devices (AVDs)  

 Click New… to display the Create new Android Virtual Device (AVD) window, then configure the optionsas shown and click Create AVD. 

Create new Android Virtual Device

Each AVD you create has many other options specified in its config.ini. You can modify this file as described at 

developer.android.com/guide/developing/devices/managing-avds.html

To more precisely match the hardware configuration of your device.

It is preferable to create a few AVDs with different API levels and hardware configurations so that your application can be tested on different versions of the Android OS. 

Once your ADV has been created, it is time to test it. Select the AVD that you want to test and click the Start… button. The Launch Options dialog will appear. If you have a small monitor, it is recommended that you check the “Scale display to real size” option so that you can set the emulator to a smaller size. Click the Launch button to start the emulator.

AVDs with different API levels 

Now all tools are ready and you will be able to learn how to write your first Android application!

Download & Installing Android SDK tools - Eclipse Tutorial

Android SDK tools and Eclipse Tutorial

In the previous tutorial we know To develop Android apps you need a Windows®, Linux or Mac OS X system  Android Developer Tools . Now I'm going to download and install Android SDK tools & eclipse tools that required for developing the first app with android.

Installing the Java Development Kit (JDK)

Android requires the Java Development Kit (JDK) version 5 or 6 (JDK 5 or JDK 6). We used JDK 6. To download the JDK for Linux or Windows, go to

www.oracle.com/technetwork/java/javase/downloads/index.html

You need only the JDK. Be sure to follow the installation instructions at

www.oracle.com/technetwork/java/javase/index-137561.html

Recent versions of Mac OS X come with Java SE 6. Be sure to get the latest version by using the Apple menu feature to check for software updates.

Android SDK

Download android sdk

You can download the Android SDK tools from developer.android.com/sdk/index.html

Click the link for your platform. Windows, Mac OS X or Linux to download the SDK’s archive file. Once you’ve downloaded the archive, simply extract its contents to a directory of your choice on your computer. Google recommends that you download the  installer_r20.0.3-windows.exe http://dl.google.com/android/installer_r20.0.3-windows.exe file instead and use it to set up the tools for you automatically. The following steps walk you through the installation process using this approach.

Download Android SDK

Installing the Android SDK Tools

When you have downloaded the installer_r20.0.3-windows.exe file, double-click it to start the installation of the Android tools. In the welcome screen of the Setup Wizard, click Next to continue If your computer does not have Java installed, you will see the error dialog shown in the picture .

Installing the Android SDK Tools

  

Note : to avoid this error you must Installing the Java Development Kit (JDK) .

You will be asked to provide a destination folder to install the Android SDK tools. Enter a destination path  and click Next.

Installing the Android SDK Tools

When the setup is done, check the “Start SDK Manager (to download system images, etc.)” option and click Finish. This will start the SDK Manager.

Note : to avoid any problem though installation runs the SDK Manger as administrator .

Installing the Android SDK Tools

Configuring the Android SDK Manager

The Android SDK Manager manages the various versions of the Android SDK currently installed on your computer. When it is launched, you will see a list of items and whether or not they are currently installed on your computer. 

Android SDK Manager

Check the relevant tools, documentation, and platforms you need for your project. Once you have selected the items you want, click the Install button to download them. Because it takes a while to download from Google’s server, it is a good idea to download only what you need immediately, and download the rest when you have more time.

NOTE  For a start, you should at least select the latest Android 4.0 SDK platform and the Extras. 

Each version of the Android OS is identified by an API level number. For example, Android 2.3.3 is level 10 (API 10), while Android 3.0 is level 11 (API 11), and so on. For each level, two platforms are available. For example, level 14 offers the following:

- SDK Platform

- Google APIs by Google Inc.

The key difference between the two is that the Google APIs platform contains additional APIs provided by Google (such as the Google Maps library). Therefore, if the application you are writing requires Google Maps, you need to create an AVD using the Google APIs platform .

You will be asked to choose the packages to install. Check the Accept All options and click Install.

Configuring the Android SDK Manager

The SDK Manager will proceed to download the packages that you have selected. The installation takes some time, so be patient. When all the packages are installed, you will be asked to restart the ADB (Android Debug Bridge). Click Yes.

Installing the Eclipse IDE 

Eclipse is the recommended integrated development environment (IDE) for Android development, though it’s possible to use other IDEs, text editors and command-line tools. To download the Eclipse IDE for Java Developers, go to www.eclipse.org/downloads/ .

This page will allow you to download the latest version of Eclipse and you will see the latest version. To use another version, click the Older Versions' link above the list of downloads. Select the appropriate version for your operating system (Windows, Mac or Linux). To install Eclipse, you simply extract the archive’s contents to your hard drive. 

On our Windows 7 system, we extracted the contents to C:\Eclipse. 

For more Eclipse installation information, see http://wiki.eclipse.org/FAQ_Where_do_I_get_and_install_Eclipse%3F

Note: when you download the example code from some site you need to configure Eclipse to use JDKX (x like 6 or 7) by performing the following steps:

1. Locate the Eclipse folder on your system and double click the Eclipse icon (eclipse.exe) to open Eclipse.

2. When the Workspace Launcher window appears, click OK.

3. Select Window > Preferences to display the Preferences window.

4. Expand the Java node and select the Compiler node. Under JDK Compliance, set Compiler compliance level to x.x(x.x like 1.6 or 1.7 etc ).

5. Close Eclipse.

 Continue to part 2 of tools that required for developing the first app with android .
Installing Android ADT Plugin For Eclipse

Build Your Own App With Android Developer Tools

Now that you know what Android is What is Android? and what its feature set contains,  Android Feature you are probably anxious to get your hands dirty and start writing some applications! 

,however Before Build your own app , All you need to start Build your own Android applications is a copy of these android tools Android SDK and the Java Development Kit (JDK). 

Unless you’re a masochist, you’ll probably want a Java integrated development environment (IDE) - Eclipse tools( app creation software) particularly well supported to make development a little bit less painful.

In this article I will focus on an overview about the required Android developer tools and SDKs . in the next article we will learn how to setup and use these tools Installing Android SDK tools.

For Android development, you can use Android development tools  on  Mac, a Windows PC, or a Linux machine. All the tools needed are free and can be downloaded from the Web. Most of the examples provided in this blog should work fine with the Android emulator. For this blog, I am using a Windows 7 computer to demonstrate all  the code samples. If you are using a Mac or Linux computer, the screenshots should look similar; some minor differences may be present, but you should be able to follow along without problems. 

Let us explore the Android development tools !

Android application development tools

JAVA JDK 

If your computer does not have the JDK installed, you should start by downloading it from oracle website . 

-  The Android SDK makes use of the Java SE Development Kit (JDK).

- jdk is the base tools for Android development tools

For more details visit this link . 

ANDROID SDK

The first and most important piece of software you need to know about it is the Android SDK. The Android Software Development Kit (SDK) contains the necessary tools to create, compile and package Android application. Most of these tools are command line based.

The Android SDK contains a debugger, libraries, an emulator, documentation, sample code, and tutorials.

- The Android SDK also provides an Android device emulator, so that Android applications can be tested without a real Android phone. 

- You can create Android virtual devices (AVD) via the Android SDK manger, which run in this emulator.

- The Android SDK contains the Android debug bridge (adb) tool which allows to connect to a virtual or real Android device.

For more details about the Android SDK and Android development tools download visit  this link   

Eclipse RESOURCE EDITORS

Eclips is the integrated development environment (IDE) for developing your Android applications. In the case of Android, the recommended IDE is Eclipse, a multi-language software development environment featuring an extensible plug-in system. 

For Android development, you should download the Eclipse IDE for Java EE Developers 

( www.eclipse.org/downloads/ ). 

ADT - ANDROID DEVELOPMENT TOOLS

Google provides the Android Development Tools (ADT) to develop Android applications with Eclipse. ADT is a set of components (plug-ins) which extend the Eclipse IDE with Android development capabilities.

ADT contains all required functionalities to create, compile, debug and deploy Android applications from the Eclipse IDE. ADT also allows to create and start AVDs.

DALVIK VIRTUAL MACHINE

The Android system uses a special virtual machine, i.e. The Dalvik Virtual Machine to run Java based applications. Dalvik uses an own bytecode format which is different from Java bytecode.

Therefore you cannot directly run Java class files on Android, they need to get converted in the Dalvik bytecode format.

HOW TO DEVELOP ANDROID APPLICATIONS

To learn  How to build an android app . first let explore code . Android code is written using Java syntax, and the core Android libraries include most of the features from the core Java APIs. Before you can run your projects, you must translate them into Dalvik bytecode. As a result, you get the familiarity of Java syntax while your applications gain the advantage of running on a VM optimized for mobile devices.

- The Java source files are converted to Java class files by the Java compiler.

- The Android SDK contains a tool called dx which converts Java class files into a .Dex (Dalvik Executable) file. 

- All class files of one application are placed in one compressed .Dex file. During this conversion process redundant information in the class files are optimized in the .dex file. For example if the same String is found in different class files, the .dex file contains only once reference of this String. These dex files are therefore much smaller in size than the corresponding class files.

-  The .dex file and the resources of an Android project, e.g. the images and XML files, are packed into an .apk (Android Package) file. The program aapt (Android Asset Packaging Tool) performs this packaging.

The resulting .apk file contains all necessary data to run the Android application and can be deployed to an Android device via the adb tool. The Android Development Tools (ADT) perform these steps transparently to the user.

If you use the ADT tooling you press a button the whole Android application (.apk file) will be created and deployed.