title: I have a crash when add DFP to my app android
body: <p>I try add DFP Banner Ads to my app , All steps have been applied in <a href="https://developers.google.com/ad-manager/mobile-ads-sdk/android/banner" rel="nofollow noreferrer">https://developers.google.com/ad-manager/mobile-ads-sdk/android/banner</a> .</p>
  
  <p>but if I open my app it crash  </p>
  
  <p>crash:</p>
  
  <pre><code>        java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.ads.doubleclick.PublisherAdView.loadAd(com.google.android.gms.ads.doubleclick.PublisherAdRequest)' on a null object reference
          at com.englishprofor.all.fragment.FragmentCategory.onCreateView(FragmentCategory.java:61)
  </code></pre>
  
  <p>FragmentCategory.class</p>
  
  <pre><code>    import android.app.Activity;
      import android.content.Context;
      import android.content.Intent;
      import android.util.Log;
      import android.view.View;
      import android.view.ViewGroup;
      import android.widget.ImageView;
      import android.widget.LinearLayout;
      import android.widget.RelativeLayout;
      import com.englishprofor.all.AppController;
      import com.englishprofor.all.Constant;
      import com.englishprofor.all.R;
      import com.englishprofor.all.activity.MainActivity;
      import com.englishprofor.all.activity.SettingActivity;
      import com.englishprofor.all.helper.CircleImageView;
      import com.englishprofor.all.helper.SettingsPreferences;
      import com.englishprofor.all.model.Category;
      import com.englishprofor.all.model.SubCategory;
      import com.google.android.gms.ads.doubleclick.PublisherAdRequest;
      import com.google.android.gms.ads.doubleclick.PublisherAdView;
      import com.google.android.gms.ads.doubleclick.*;
  
      import java.util.ArrayList;
  
      public class FragmentCategory extends Fragment {
          private static final String TAG = "FragmentCategory";
      Context con ;
          private RecyclerView recyclerView;
          private View view;
          ArrayList&lt;Category&gt; mListItem;
          //AdView mAdView;
          private PublisherAdView mPublisherAdView;
  
          TextView empty_msg, tvTitle;
          CoordinatorLayout layout;
          ImageView back, setting;
          public static ArrayList&lt;Category&gt; categoryList;
          public static ArrayList&lt;SubCategory&gt; subCatList;
  
  
          @Override
          public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
              view = inflater.inflate(R.layout.fragment_category, container, false);
              mPublisherAdView = view.findViewById(R.id.publisherAdView);
              PublisherAdRequest adRequest = new PublisherAdRequest.Builder().build();
      mPublisherAdView.loadAd(adRequest);
  </code></pre>
  
  <p>fragment_category.xml</p>
  
  <pre><code>        &lt;?xml version="1.0" encoding="utf-8"?&gt;
      &lt;android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:app="http://schemas.android.com/apk/res-auto"
          xmlns:ads="http://schemas.android.com/tools"
          android:id="@+id/layout"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:background="@drawable/background"&gt;
  
          &lt;RelativeLayout
              android:layout_width="match_parent"
              android:layout_height="match_parent"
             &gt;
              &lt;include layout="@layout/actionbar_layout"/&gt;
  
  
          &lt;android.support.v7.widget.RecyclerView
              android:id="@+id/category_recycleview"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:layout_below="@+id/relativeLayout"
              android:layout_above="@+id/banner_AdView"/&gt;
  
          &lt;TextView
              android:id="@+id/txtblanklist"
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_centerInParent="true"
              android:gravity="center"
              android:textColor="@color/black"
              android:textSize="15dp"
              android:textStyle="bold"
              android:visibility="gone" /&gt;
  
              &lt;com.google.android.gms.ads.doubleclick.PublisherAdView
                  android:id="@+id/banner_AdView"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  android:layout_centerHorizontal="true"
                  android:layout_alignParentBottom="true"
                  ads:adSize="BANNER"
                  ads:adUnitId="/6499/example/banner"&gt;
              &lt;/com.google.android.gms.ads.doubleclick.PublisherAdView&gt;
  
                  &lt;/RelativeLayout&gt;
              &lt;/android.support.design.widget.CoordinatorLayout&gt;
  </code></pre>
  
  <p>please help me , I want enable DFP in my app </p>
  
  <p>thanks for all </p>