Develop First App in Android

1. Android SDK Kit
You can get the latest version of the SDK starter package from the SDK download page. Make sure to download the package that is appropriate for your development computer.
 
2. Installing the ADT Plugin for Eclipse
Follow instruction mentioned at Eclipse ADT Installation and Configuration

3. Launching the Android SDK and AVD Manager
The Android SDK and AVD Manager is the tool that you use to install and upgrade SDK components in your development environment.

You can access the tool in any of three ways:

    * If you are developing in the Eclipse IDE with the ADT Plugin, you can access the tool directly from the Eclipse UI.
    * On Windows only, you can launch he tool by double-clicking a script file.
    * In all environments, you can access the tool from a command line.

Launching from Eclipse/ADT

If you are developing in Eclipse and have already installed the ADT Plugin, follow these steps to access the Android SDK and AVD Manager tool:
   1. Open Eclipse
   2. Select Window > Android SDK and AVD Manager.
HelloAndroid.java

package com.example.helloandroid;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;

public class HelloAndroid extends Activity {
   /** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       TextView tv = new TextView(this);
       tv.setText("Anuj, Congo for First Android App");
       setContentView(tv);
   }
}