title: Game Services classes Cannot be resolved
body: <p>I want to implement Google Play Game Services. But in GameHelper class the following classes could not be found at compilation.</p>
  
  <p>import com.google.android.gms.games.Games;</p>
  
  <p>import com.google.android.gms.appstate.AppStateManager;</p>
  
  <p>import com.google.android.gms.games.multiplayer.Multiplayer;</p>
  
  <p>import com.google.android.gms.plus.Plus;</p>
  
  <p>Error: </p>
  
  <p>The import com.google.android.gms.appstate.AppStateManager cannot be resolved   GameHelper.java</p>
  
  <p>I already read the google docs about Game Services and made all like that. In App Billings works great. So I have integrated the library project of Google Play Services in the right way.</p>
  
  <p>Does anyone know something about this problem?</p>