RUNNING THE APP

RUNNING THE HELLO WORLD APP


        If you see the previous post to create an android project, it includes a default set of "HELLO WORLD" source files that allow you to immediately run the app.

How to run your app depends on two things: whether you have a real Android-powered device and whether you're using Eclipse. This lesson shows you how to install and run your app on a real device and on the Android emulator, and in both cases with either Eclipse or the command line tools.

Before you run your app, you should be aware of a few directories and files in the Android project:

AndroidManifest.xml

The manifest file describes the fundamental characteristics of the app and defines each of its components. You'll learn about various declarations in this file as you read more training classes.

One of the most important elements your manifest should include is the <uses-sdk> element. This declares your app's compatibility with different Android versions using the android:minSdkVersion andandroid:targetSdkVersion attributes. For your first app, it should look like this:

<manifest xmlns:android="http://schemas.android.com/apk/res/android" ... >
    <uses-sdk android:minSdkVersion="8" android:targetSdkVersion="17" />
    ...
</manifest>

You should always set the android:targetSdkVersion as high as possible and test your app on the corresponding platform version. For more information, read Supporting Different Platform Versions.

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. Here are just a few:

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 a Real Device

If you have a real Android-powered device, here's how you can install and run your app:

1.    Plug in your device to your development machine with a USB cable. If you're developing on Windows, you might need to install the appropriate USB driver for your device. For help installing drivers, see the OEM USB Drivers document.

2.    Enable USB debugging on your device.

o    On most devices running Android 3.2 or older, you can find the option under Settings > Applications > Development.

o    On Android 4.0 and newer, it's in Settings > Developer options.

To run the app from Eclipse:

1.    Open one of your project's files and click Run from the toolbar.

2.    In the Run as window that appears, select Android Application and click OK.

Eclipse installs the app on your connected device and starts it.

Or to run your app from a command line:

1.    Change directories to the root of your Android project and execute:

ant debug

2.    Make sure the Android SDK platform-tools/ directory is included in your PATH environment variable, then execute:

adb install bin/MyFirstApp-debug.apk

3.    On your device, locate MyFirstActivity and open it.

Run on the Emulator

Whether you're using Eclipse or the command line, to run your app on the emulator you need to first create an Android Virtual Device (AVD). An AVD is a device configuration for the Android emulator that allows you to model different devices.

                 Figure 1. The AVD Manager showing a few virtual devices.

To create an AVD:

1.    Launch the Android Virtual Device Manager:

a.     In Eclipse, click Android Virtual Device Manager from the toolbar.

b.    From the command line, change directories to<sdk>/tools/ and execute:

android avd

2.    In the Android Virtual Device Manager panel, click New.

3.    Fill in the details for the AVD. Give it a name, a platform target, an SD card size, and a skin (HVGA is default).

4.    Click Create AVD.

5.    Select the new AVD from the Android Virtual Device Manager and click Start.

6.    After the emulator boots up, unlock the emulator screen.

To run the app from Eclipse:

1.    Open one of your project's files and click Run  from the toolbar.

2.    In the Run as window that appears, select Android Application and click OK.

Eclipse installs the app on your AVD and starts it.

CREATING ANDROID HELLO WORLD APP

An Android project contains all the files that comprise the source code for your Android app. The Android SDK tools make it easy to start a new Android project with a set of default project directories and files.

This Post shows how to create a new project either using Eclipse.

Create a "Hello World" with Eclipse

1.    Click New in the toolbar.

2.    In the window that appears, open the Android folder, select Android Application Project, and click Next.

Figure 1. The New Android App Project wizard in Eclipse.

3.    Fill in the form that appears:

o    Application Name is the app name that appears to users. For this project, use "My First App."

o    Project Name is the name of your project directory and the name visible in Eclipse.

o    Package Name is the package namespace for your app (following the same rules as packages in the Java programming language). Your package name must be unique across all packages installed on the Android system. For this reason, it's generally best if you use a name that begins with the reverse domain name of your organization or publisher entity. For this project, you can use something like "com.example.myfirstapp." However, you cannot publish your app on Google Play using the "com.example" namespace.

o    Minimum Required SDK is the lowest version of Android that your app supports, indicated using the API level. To support as many devices as possible, you should set this to the lowest version available that allows your app to provide its core feature set. If any feature of your app is possible only on newer versions of Android and it's not critical to the app's core feature set, you can enable the feature only when running on the versions that support it. Leave this set to the default value for this project.

o    Target SDK indicates the highest version of Android with which you have tested with your application.

As new versions of Android become available, you should test your app on the new version and update this value to match the latest API level in order to take advantage of new platform features.

o    Compile With is the platform version against which you will compile your app. By default, this is set to the latest version of Android available in your SDK. You can still build your app to support older versions, but setting the build target to the latest version allows you to enable new features and optimize your app for a great user experience on the latest devices.

o    Theme specifies the Android UI style to apply for your app. You can leave this alone.

Click Next.

4.    On the next screen to configure the project, leave the default selections and click Next.

5.    The next screen can help you create a launcher icon for your app.

Click Next.

6.    Now you can select an activity template from which to begin building your app.

For this project, select BlankActivity and click Next.

7.    Leave all the details for the activity in their default state and click Finish.

JAVA FUNDAMENTALS

UNIT-I   JAVA FUNDAMENTALS

MODULE-I BASICS OF JAVA

INTRODUCTION TO JAVA

   Java Technology is

*A Programming Language

*A Development Environment

*An Application Environment

*A Deployment Environment

  It is originally developed by James Gosling, Sun Microsystems and now it is developing by oracle. Very first, the java is called as oak.

  It is a language, easy to program because,

  It is eliminating many pitfalls of other language such as pointer, memory management.

  It is fast, secure, and reliable.

  It is platform independent can run in any environment (since java codes are converted into byte codes)

  Before Learning about java you should be aware of the below things..

JVM

            Java Virtual Machine  which means imaginary machine. The java program is compiled by the compiler and converts into byte code (.class files) i.e., machine code then it is verified and run in interpreter.

GARBAGE COLLECTION

To allocate/deallocate memory pointers should be used in other programming languages whereas here there is no need of pointers.

Garbage collection happens automatically during the lifetime of java program, eliminating the need to deallocate the memory and also avoiding the memory leaks

JRE

            Java Runtime Environment, it will load the code then verify the code and finally executes code.

MODULE-II OOPS CONCEPTS

            I hope you are all well known about oops concept. So I skip this chapter.

MODULE-III IDENTIFIER, KEYWORDS AND TYPES

IDENTIFIER:

            Identifier is a name given to a variable, class or method.

            Following are valid identifiers to be used in JAVA:

Username

username

user_name

_username

$username

KEYWORDS:

Abstract	Continue	For	New	Switch
Assert	Default	Goto	Package	Synchronized
Boolean	Do	If	private	This
Break	Double	Implements	Protected	Throw
Byte	Else	Import	Public	Throws
Case	Enum	instanceof	Return	transient
Catch	Extends	Int	Short	Try
Char	Final	Interface	Static	Void
Class	Finally	long	Strictfp	Volatile

DATA TYPES

Eight primitive data types are there in java programming language,

à   Logical- boolean

e.g.: boolean a=true;

à   Textual- char

e.g.: char a=’a’;

à   Integral- byte, short, int and long

à   Floating point- double and float

e.g.:double a=3.1415;

       float a=3.414f

STRING

String is not a primitive data type; it is a class to represent the sequence of the character.

e.g: String a=”hai, how are you”;

MODULE-IV EXPRESSION & FLOW CONTROL

VARIABLES & SCOPE

There are two ways to describe variables:

à   Variable of primitive type

à   Variable of reference type

We can declare variable inside a method or outside a method.

Variable which is defined inside a method is called local variable. Sometime this is also called as automatic, temporary or stacks variables.

Variable defined outside a method are created when the object is constructed using the new abc() call. Variable can be define outside a method in two ways,

à   Using static keyword is called class variable.

à   Without using static keyword is called as instance variable or member variable.

DEFAULT VALUE OF PRIMITIVE TYPES

VARIABLE	VALUE
Byte	0
Short	0
Int	0L
Long	0.0F
Float	0.0D
Double	‘\u0000’
Boolean	False
All reference types	null

OPERATORS

Important types of operators are there in java programming language.

à   Arithmetic Operator (+, -, *, /)

à   Logical Operator (AND (&), OR (|), NOT (!), XOR (^))

à   Short-circuit logical Operator (&&, ||)

*****END*****

UNIT-II JAVA STANDARD EDITION (J2SE)

MODULE I STRUCTURE OF JAVA

Package name i.e., our project name

STRUCTURE

Similar to header file

package javaapplication3;

import java.lang.*; 

public class Main

{

Main function should be within the class

    public static void main(String[] args)

   {

              System.out.println(“hello”);

   }

}

public static void main(String[] args)

public :- The method main() can be accessed by anything including interpreter.

Static :- This keyword tells the compiler that the main() method is used in the class. There is no need of instance to execute the static method.

Void :- it indicates that the main function should not return any value.

String args[] :- the main method is declare with a single parameter “args” which is a type of String array.

COMPILING AND RUNNING THE JAVA PROGRAM

Step1: Type the program in a notepad and save as classname.java and place it in the C:\Program Files\Java\jdk1.7.0_17\bin

Step2 : open the command prompt change the path to C:\Program Files\Java\jdk1.7.0_17\bin and then to compile type javac classname.java, to run type java classname

Step3 : output will be displayed.

Instead running the program in command prompt better we can use IDE like netbeans or eclipse.