Implementing Google Map API v2 in Android

1.       Install Google Play Services SDK

       Make sure you include this library in your project when you get to coding!

2.        Generate the debug key from a terminal prompt:

In command line go to JRE bin path and execute below command

keytool -list -v -keystore "C:\Users\Sujay.A\.android\debug.keystore" -alias androiddebugkey -storepass android -keypass android

   3.       Go to the Google APIs Console and Create a New Project. 
          Scroll down to "Google Maps Android API V2" and set the switch to On

4. Paste in your SHA1 key (from Step 2 above), semicolon, application package name ie, 7F:8B:BF:C1:6E:86:7F:5C:83:15:EA:BE:1F:B4:A3:C6:3D:70:51:22;com.sujay

Copy the API key: AIzaSyDtaCSEX37WV_g-sd5CxhOMh6Q26oBApZg

5. Add API key application

In AndroidManifest.xml, add the following element as a child of the <application> element, by inserting it just before the closing tag </application>:
<meta-data
    android:name="com.google.android.maps.v2.API_KEY"     android:value="API_KEY"/> 
Substitute your API key for API_KEY in the value attribute. This element sets the keycom.google.android.maps.v2.API_KEY to the value of your API key, and makes the API key visible to any MapFragment in your application.
Also include
 <meta-data    android:name="com.google.android.gms.version"    android:value="@integer/google_play_services_version" /> 
Add permissions in manifest :
<uses-permission android:name="android.permission.INTERNET" /><uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /><uses-permission android:name="com.codebybrian.mapsample.permission.MAPS_RECEIVE" /><uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
<!-- Optional permissions -->
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" /><uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-featureandroid:glEsVersion="0x00020000"android:required="true" />
<permissionandroid:name="com.codebybrian.mapsample.permission.MAPS_RECEIVE"android:protectionLevel="signature" />

6.      Include the "google-play-services" library downloaded in Step 1 in your project

      7.      Create a little sample project, like I have below.

import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.FragmentManager;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.MapFragment;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;

public class MyMapsActivity extends Activity {
    private GoogleMap googleMap;
    private int mapType = GoogleMap.MAP_TYPE_NORMAL;

    @SuppressLint("NewApi")
       @Override    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.mymap);

        FragmentManager fragmentManager = getFragmentManager();
        MapFragment mapFragment =  (MapFragment) fragmentManager.findFragmentById(R.id.map);
        googleMap = mapFragment.getMap();

        LatLng sfLatLng = new LatLng(37.7750, -122.4183);
        googleMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
        googleMap.addMarker(new MarkerOptions()
                .position(sfLatLng)
                .title("San Francisco")
                .snippet("Population: 776733")
                .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_AZURE)));

        LatLng sLatLng = new LatLng(37.857236, -122.486916);
        googleMap.addMarker(new MarkerOptions()
                .position(sLatLng)
                .title("Sausalito")
                .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_VIOLET)));


        googleMap.getUiSettings().setCompassEnabled(true);
        googleMap.getUiSettings().setZoomControlsEnabled(true);
        googleMap.getUiSettings().setMyLocationButtonEnabled(true);


        LatLng cameraLatLng = sfLatLng;
        float cameraZoom = 10;

        if(savedInstanceState != null){
            mapType = savedInstanceState.getInt("map_type", GoogleMap.MAP_TYPE_NORMAL);

            double savedLat = savedInstanceState.getDouble("lat");
            double savedLng = savedInstanceState.getDouble("lng");
            cameraLatLng = new LatLng(savedLat, savedLng);

            cameraZoom = savedInstanceState.getFloat("zoom", 10);
        }

        googleMap.setMapType(mapType);
        googleMap.animateCamera(CameraUpdateFactory.newLatLngZoom(cameraLatLng, cameraZoom));
    }

    @Override    public boolean onCreateOptionsMenu(Menu menu) {
        super.onCreateOptionsMenu(menu);
        getMenuInflater().inflate(R.menu.map_styles_menu, menu);
        return true;
    }

    @Override    public boolean onOptionsItemSelected(MenuItem item) {
        super.onOptionsItemSelected(item);

        switch(item.getItemId()){
            case R.id.normal_map:
                mapType = GoogleMap.MAP_TYPE_NORMAL;
                break;

            case R.id.satellite_map:
                mapType = GoogleMap.MAP_TYPE_SATELLITE;
                break;

            case R.id.terrain_map:
                mapType = GoogleMap.MAP_TYPE_TERRAIN;
                break;

            case R.id.hybrid_map:
                mapType = GoogleMap.MAP_TYPE_HYBRID;
                break;
        }

        googleMap.setMapType(mapType);
        return true;
    }

    @Override    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);

        // save the map type so when we change orientation, the mape type can be restored        LatLng cameraLatLng = googleMap.getCameraPosition().target;
        float cameraZoom = googleMap.getCameraPosition().zoom;
        outState.putInt("map_type", mapType);
        outState.putDouble("lat", cameraLatLng.latitude);
        outState.putDouble("lng", cameraLatLng.longitude);
        outState.putFloat("zoom", cameraZoom);
    }
}
 
 
 
Make sure you use ICS and above
 
res/menu/map_styles_menu.xml :
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:id="@+id/map_types"
          android:icon="@drawable/map_menu"
          android:title="Select map type"
          android:showAsAction="always">
        <menu>
            <item android:id="@+id/normal_map"
                  android:title="Normal map"/>
            <item android:id="@+id/satellite_map"
                  android:title="Satellite map"/>
            <item android:id="@+id/terrain_map"
                  android:title="Terrain map"/>
            <item android:id="@+id/hybrid_map"
                  android:title="Hybrid map"/>
        </menu>
    </item>
</menu>
 
 
mymap.xml:
<?xml version="1.0" encoding="utf-8"?>
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
          android:id="@+id/map"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          class="com.google.android.gms.maps.MapFragment"/>

OutPut:

If you are using 2.3

Extend the class from FragmentActivity

and replace 

Fragment manager with below line:

SupportMapFragment fm = (SupportMapFragment)getSupportFragmentManager().findFragmentById(R.id.map);

Source:

https://developers.google.com/maps/documentation/android/start#installing_the_google_maps_android_v2_api