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

  

Common Android development problems and their solution

Things are not always working as they should during your Android development. This section gives an overview over typical problems and how to solve them.

1.1. Clean Project

Several users report that they get the following errors:

1. Project ... is missing required source folder: 'gen'
2. The project could not be built until build path errors are resolved.
3. Unable to open class file R.java.

To solve any of these errors, go to the project menu and select Project → Clean.

If you have library projects, make sure to clean them too.

1.2.  android.content.ActivityNotFoundException

During start or during execution of your application, your application stops. In the LogCat view you see the message:android.content.ActivityNotFoundException : Unable to find explicit activity class; have you declared this activity in your AndroidManifest.xml?

Check in this case if you declared your activity in the AndroidManifest.xml file.

1.3. Problems with Android Debug Bridge (adb)

The communication with the emulator or your Android device might have problems. This communication is handled by the Android Debug Bridge (adb).

Eclipse allows to reset the adb in case this causes problems. Select therefore the DDMS perspective via Window →Open Perspective → Other → DDMS

To restart the adb, select the "Reset adb" in the Device View.

1.4. LogCat

The LogCat view shows you the log messages of your Android device and helps you to analyze problems. For example Java exceptions in your program would be shown here. To open this view, select Window → Show View → Other →Android → LogCat.

1.5. Java7

If Android complains that you cannot use Java7 select your right-click on your project and select the Java Compiler entry. Ensure that Java 1.5 or Java 1.6 is used. You may have to select the Enable project specific settings checkbox.

1.6. Eclipse reports file from R.java as missing

Sometimes Eclipse complains that a file, e.g. R.layout.main cannot be found. Check in your source code that you did not import android.R. An android.R import will prevent Eclipse from finding your R file.

1.7. Android editor not opened

Android provides nice editors to edit Android resource files, unfortunately these editor are not always automatically used due to bugs in the ADT. If that happens, you can open this editor manually. Right-click on your menu file and select Open with → Android Menu Editor.

1.8. Emulator does not start

If your emulator does not start, make sure that the android-sdk version is in a path without any spaces in the path name.

1.9. Timeout during deployment

If you face timeout issues during deployment you can increase the default timeout in the Eclipse preferences. SelectWindow → Preferences → Android → DDMS and increase the ADB connection timeout (in ms) value.

1.10. Installation failed due to insufficient storage

Sometimes the emulator will refuse to install an application with the error message: INSTALL_FAILED_INSUFFICIENT_STORAGE.

An Android virtual device provides by default only 64M for the storaging Android applications. You can clean your installed application by re-starting the emulator and selecting the Wipe user data " flag.

Alternatively you can set the data partition size. If you press edit on the AVD, you can set the Ideal size of data partition property via the New button.

1.11. Debug Certificate expired

If you get the error message Debug Certificate expired switch to the folder which contains the Android AVD, e.g..android under Linux and delete the debug.keystore file. This file is only valid for a year and if not present, Eclipse will regenerate the password.

1.12. Error message for @Override

The @Override annotation was introduced in Java 1.6. If you receive an error message for @Override, change the Java compiler level to Java 1.6. To do this, right-click on the project, select Properties → Java Compiler → Compiler compliance level and select 1.6 in the drop-down box.

1.13. Missing Imports

Java requires that classes which are not part of the standard Java Language are either fully qualified or declared via imports.

If you see an error message with the XX cannot be resolved to a variable text, right-click in your Editor and selectSource → Organize Imports to important required packages.

Essential steps to start android development

Welcome to Mobile app development

         Now-a-days Android is one of the most popular operating system for Mobiles , as on it occupies 75% of market in present . So the essential steps and resources to start as an Android developer are as follows.

Step 1 : Make knowledge on Mobile Platforms & devices .

Step 2 : Now download the resources that need for development .

Step 3 : As on for Android you can know the latest version and features from this site   http://www.android.com/ .

Step 4 : For Android development you need Eclipse , Android SDK and ADT plugin  where you can download from http://developer.android.com/sdk/index.html .

Step 5 : Now you can extract the ADT bundle which consists of eclipse , android sdk  and ADT plugin .

Step 6 : So  follow the procedure from this link to install Android SDK in to eclipse and aslo ADT plugin and you can start developing the Android apps .