How to build a simple App in android

Click File  Select New option in the toolbar.

Then Select Android Application project in the  New  .

Now enter the Application Name , Project name & Package name as show on below image.

Click Next 

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

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

You can customize an icon in several ways and the tool generates an icon for all screen  densities.     Before you publish your app, you should be sure your icon meets the specifications defined in the Iconographydesign guide.

Click Next.

Now you can select an activity template from which to begin building your app. For this project, select BlankActivity and click Next.

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

New Android application

  

Activity and layout name

  

Now Select your project on Package Explorer in eclipse and click on that it consists folder structure like this as shown on the image .

Package explore

Now click on the Src folder which consists of  Java Class files named as Activities in android terminology.

So we can also see the remaining folders such as bin , res folder which is very important, res is the Resource folder which consists of drawable , layouts ,values etc.....

 Now we will see how to run the android project to build a app .

 Right Click on the project and select Run as option and click  on Android application which is  shown below.

Running android application

 So final your First Android app is Successfully installed in the Emulator .

Output in emulator