Hello World Android Tutorial

In this tutorial, we shall go through the various steps of creating a sample android “Hello World” app. We shall also see how to set up the Eclipse IDE. Once our application is ready, we will launch the application and see it working on the Android Virtual Device and also ways to run it on a real android device.

Prerequisites:

1.     JDK 1.6

2.     Eclipse IDE 3.7

3.     Android SDK

The flow of this tutorial shall be as follows :

1.     Install Android SDK

2.     Install ADT Eclipse plug-in

3.     Create an Android Virtual Device (AVD)

4.     Create an Android Project

5.     Code the app

6.     Run the app on AVD

7.     Run the app on a real android device

 1. Install Android SDK

Visit this Android SDK page, select the platform you need, based on your Operating System and its version - 32 bit (X86) or 64 bit (X64), and install it.

Run the “Android SDK manager” and choose the Android versions you want to develop your app for.

2. Install ADT Eclipse Plug-in

To integrate the Android SDK with Eclipse IDE, you need to install Eclipse ADT plug-in. The ADT package which you downloaded from developer.android.com is compressed and you need to extract the contents to access the setup files. You may refer to this official guide - “Installing the ADT Plugin“.

3. Create An Android Virtual Device (AVD)

In Eclipse, you can access the “Android Virtual Device” (AVD) in Eclipse toolbar. Click “New” to create a new AVD. Select the device, android version and the processor type. This AVD may then be used to deploy the applications.

4. Create An Android Project

In Eclipse, select “File > New > Project > Android Project”, and input your application detail. Eclipse will create all the necessary Android project files and configuration.

Fill in the following fields on the first screen

·         Application Name: It is the name of your app. This name is visible on the screen when the app is installed. The application name is also shown in the android stores when you upload your application.

·         Project Name: It is the name of the project that gets created in eclipse. You can give any name to your project.

·         Package Name: It is used to uniquely identify your application on Play Store. You should always follow the java package convention for the package name. The package name is not visible to the user but it should never change. A good approach to choose package name is to use the reverse of your company domain name. For example, if your URL is “example.com” the ideal package name would be “com.example.android”.

·         Minimum Required SDK: This field gives you the flexibility to decide which minimum version of android you wish to support. For example, if you create an application for android 2.2 it will work on all android versions above android 2.2.

·         Target SDK: This field says that even though your app will be able to run on its previous android versions, but it is explicitly tested with the version specified in this field.

·         Compile With: This option lets you choose the version of SDK you wish to compile with. Typically, the highest version which is available in your ADT should be chosen here. This would compile your app with the latest code and optimizations.

·         Theme: When creating apps for version 4.X and above, you may choose to have an application wide theme. These themes are pre-defined color schemes, which you can use to improve your application's User Interface.

You have the following fields here:

·         Create Custom Launcher Icon:  This icon is the launcher icon which will be displayed on screen. If this option is checked, ADT will launch a wizard to create launcher icon. Keep this option selected.

·         Create Activity: With this option selected, ADT will create the first activity for you. This will be your main activity and will have a reference in the AndroidManifest.xml file.

·         Mark This project as Library: An android project may be of 2 types: library project or a non-library project. A library project is a reusable project which is used by other non library projects. Library project cannot be installed.

·         Create Project in Workspace: When you open Eclipse for the first time, it asks you to choose a workspace. Workspace is a location on your hard disk where all of your projects will be saved. With this checkbox selected, you tell the ADT to save this project in the current location. If you wish to store your project at some other location, you can uncheck this option and select the desired path to save the project

·         Add Project to working sets: Working Set can be used to group similar projects together. When your number of projects starts increasing, you can group them together into working sets to avoid seeing all projects while working. You may ignore this option for now.

If you checked create custom launcher check box on Screen 2, Screen 3 will be for the creation of launcher icon. On this screen, you can put together different options to create a launcher icon. You can choose your own image, text or even your clip-arts. In the right pane, you can see the preview of the icon. You can experiment with different options like background color, shape etc and finalize an icon based on preview.

Screen 4 is an activity template screen. ADT is pre bundled with some activity templates. These templates have predefined structures and they automatically generate the required code for you.

·         Blank Activity: This will create a blank activity with 1 Textview.

·         Full Screen Activity: This activity hides the status bar so that your activity can take all screen space.

·         Master Detail Flow: This template creates advanced navigation, based on fragments, which will work on both tablets and phones without any change.

For the sake of this app, select Blank activity and click Next.

This screen is an Activity configuration screen. This screen helps you in configuring the relevant options.

·         Activity Name: This will be the name of your activity to be created.

·         Layout Name: An activity always has a user interface with it. Since ADT is creating an activity for you, it will also create a layout for you to bind it with the activity.

·         Navigation Type: This option lets you choose the navigation type for your activity. Select None and click Finish.

Once you click Finish, a new project and will be created. Java code and Layout code files shall be opened.

5. Code The App

Locate the generated activity file, and modify a bit to output a string “Hello World”.

NOTE: If the default java file is with the name MainActivity.java, do not change the class name to HelloWorld.

File : HelloWorld.java

package com.example.android;

import android.app.Activity;

import android.os.Bundle;

import android.widget.TextView;

public class HelloWorld extends Activity

{

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

    @Override

    public void onCreate(Bundle savedInstanceState)

        {

        super.onCreate(savedInstanceState);

        TextView text = new TextView(this);

        text.setText("Hello World");

        setContentView(text);

        }

}

6.  Run the app on AVD

Run the project as “Android Application“, choose the AVD and see the output.

7.  Run the app on a real android device

Connect your android device to your PC through the USB cable. Make sure that USB Debugging is allowed on the device.

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

* On Android 4.0 and newer, it is in Settings > Developer options.

Run the project as “Android Application“, choose your android device from the list and see the output.