package com.udacity.gradle.builditbigger;

import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

/**
 * A placeholder fragment containing a simple view.
 */
public class MainActivityFragment extends Fragment {

    public MainActivityFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View root = inflater.inflate(R.layout.fragment_main, container, false);

       // AdView mAdView = (AdView) root.findViewById(R.id.adView);
        // Create an ad request. Check logcat output for the hashed device ID to
        // get test ads on a physical device. e.g.
        // "Use AdRequest.Builder.addTestDevice("ABCDEF012345") to get test ads on this device."
       // AdRequest adRequest = new AdRequest.Builder()
        //        .addTestDevice(AdRequest.DEVICE_ID_EMULATOR)
        //        .build();
       // mAdView.loadAd(adRequest);
        return root;
    }
}

package com.udacity.gradle.builditbigger;

import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

/**
 * A placeholder fragment containing a simple view.
 */
public class MainActivityFragment extends Fragment {

    public MainActivityFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View root = inflater.inflate(R.layout.fragment_main, container, false);

        return root;
    }
}

Clean fragment code