Publishing ads in Android Applications using Google AdMob

step1:Add google play services library to the project.
         To know how to add library project visit this post :http://ramsandroid4all.blogspot.in/2013/03/google-maps-android-api-v2.html

step2:Register application in www.admob.com and get publisher ID

step3:Add following code in java class

MainActivity.java:
-------------------
package com.ram.displayallcontacts;

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

import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdSize;
import com.google.android.gms.ads.AdView;

public class MainActivity extends Activity {
    /** The view to show the ad. */
    private AdView adView;

    /* Your ad unit id. Replace with your actual ad unit id. */
    private static final String AD_UNIT_ID = "a152ce2b1c542db";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.ad);

        // Create an ad.
        adView = new AdView(this);
        adView.setAdSize(AdSize.BANNER);
        adView.setAdUnitId(AD_UNIT_ID);

        // Add the AdView to the view hierarchy. The view will have no size
        // until the ad is loaded.
        LinearLayout layout = (LinearLayout) findViewById(R.id.ll);
        layout.addView(adView);

       // Start loading the ad in the background.
        adView.loadAd(new AdRequest.Builder().build());

    }

    @Override
    public void onResume() {
        super.onResume();
        if (adView != null) {
            adView.resume();
        }
    }

    @Override
    public void onPause() {
        if (adView != null) {
            adView.pause();
        }
        super.onPause();
    }

    /** Called before the activity is destroyed. */
    @Override
    public void onDestroy() {
        // Destroy the AdView.
        if (adView != null) {
            adView.destroy();
        }
        super.onDestroy();
    }
}

step4:Add following tags under AndroidManifest.xml -->application tag and add internet permissions as follows
AndroiManifest.xml:
-------------------------
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.ram.displayallcontacts"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="19" />

     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.INTERNET" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.ram.displayallcontacts.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="com.google.android.gms.ads.AdActivity"
            android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize" />

        <meta-data
            android:name="com.google.android.gms.version"
            android:value="@integer/google_play_services_version" />
    </application>

</manifest>