How to add ads to an android app using eclipse?

I can't add ads to my app using the new admob. I have tried alot of things but they don't work this is what my code is like, this is the conclusion that I ended up with

here is my xml:

<LinearLayout xmlns:android="http://ift.tt/nIICcg"
xmlns:ads="http://ift.tt/GEGVYd"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:weightSum="3"
android:background="@android:color/background_dark" >

<RelativeLayout
    android:id="@+id/adBanner"
    android:layout_width="fill_parent"
    android:layout_height="50dp"
    android:gravity="center">

        <com.google.android.gms.ads.AdView 
            android:id="@+id/adView"
            android:layout_width="320dp"
            android:layout_height="50dp"
            ads:adUnitId="bla bla"
            ads:adSize="BANNER"
            android:layout_gravity="center"/>

    </RelativeLayout>

   .......

</LinearLayout>

and I getting an error:

The following classes could not be instantiated:
- com.google.android.gms.ads.AdView

here is my java:

import java.io.IOException;

import com.squareup.picasso.Picasso;
import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdView;
import android.app.Activity;
import android.app.WallpaperManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.Window;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {

static int tophone;
ImageView display;
  private AdView adView;


 protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
    setContentView(R.layout.activity_main);


    AdRequest adRequest = new AdRequest.Builder()
    .build();


    AdView adView = (AdView) this.findViewById(R.id.adView);
    adView.loadAd(adRequest);

    ........

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

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

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

my manifest:

 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://ift.tt/nIICcg"
package="com.StarSurge.khwallpaper"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk
    android:minSdkVersion="11"
    android:targetSdkVersion="21"/>
<uses-permission android:name="android.permission.SET_WALLPAPER"/>
<uses-permission android:name="android.permission.SET_WALLPAPER_HINTS"/>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <meta-data android:name="com.google.android.gms.version"
    android:value="@integer/google_play_services_version" />
    <activity
        android:name=".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"/>
</application>

  </manifest>

so could anyone tell me what should I do to fix the error and to make the add work?