• Application Class that extends from Aplication
public class App extends Application{

    private static Context mContext;

    @Override
    public void onCreate() {
        super.onCreate();
        mContext = getApplicationContext();
        FacebookSdk.sdkInitialize(mContext);
        //Other Initialisations
    }
}

Change Android name to Application node:

android:name="App"

<application
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:name="App" >

Source#