title: Blank screen on GridView
body: <p>I'm trying to create a GridView with an array of strings. These are XML, and MainActivity and Adapter, but what I get is a blank screen. I'm change the background, but the result is the same, but clicking on a point on the screen appears to me the toast stating that the number has been selected. Any thoughts ?</p>
  
  <p>XML:</p>
  
  <pre><code>    GridView xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
     android:layout_height="match_parent"
     tools:context=".MainActivity"
     android:columnWidth="90dp"
     android:numColumns="auto_fit"
     android:verticalSpacing="10dp"
     android:stretchMode="columnWidth"
     android:gravity="center"
     android:id="@+id/gridview"&gt;
  &lt;/GridView&gt;
  </code></pre>
  
  <p>MainActivity:</p>
  
  <pre><code>    package kangel.customtest;
  
  import android.support.v7.app.ActionBarActivity;
  import android.os.Bundle;
  import android.view.Menu;
  import android.view.MenuItem;
  import android.view.View;
  import android.widget.AdapterView;
  import android.widget.GridView;
  import android.widget.Toast;
  
  
  public class MainActivity extends ActionBarActivity {
      GridView gridView;
  
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
          gridView = (GridView)findViewById(R.id.gridview);
          gridView.setAdapter(new NumberAdapter(this));
          gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
              @Override
              public void onItemClick(AdapterView&lt;?&gt; parent, View view, int position, long id) {
                  Toast.makeText(getBaseContext(),"Hai selezionato il numero "+position, Toast.LENGTH_LONG).show();
              }
          });
      }
  }
  </code></pre>
  
  <p>Adapter:</p>
  
  <pre><code>    package kangel.customtest;
  
  import android.content.Context;
  import android.view.View;
  import android.view.ViewGroup;
  import android.widget.AbsListView;
  import android.widget.BaseAdapter;
  import android.widget.GridView;
  import android.widget.ImageView;
  import android.widget.TextView;
  
  /**
   * Created by Andrea on 22/06/2015.
   */
  public class NumberAdapter extends BaseAdapter {
  
      private Context context;
      private String numeriGiocabili[]=
              {"1","2","3","4","5","6","7","8","9","10",
              "11","12","13","14","15","16","17","18","19","20",
              "21","22","23","24","25","26","27","28","29","30",
              "31","32","33","34","35","36","37","38","39","40",
              "41","42","43","44","45","46","47","48","49","50",
              "51","52","53","54","55","56","57","58","59","60"};
  
      public NumberAdapter(Context context){
          this.context = context;
      }
      @Override
      public int getCount() {
          return numeriGiocabili.length;
      }
  
      @Override
      public Object getItem(int position) {
          return null;
      }
  
      @Override
      public long getItemId(int position) {
          return 0;
      }
  
      @Override
      public View getView(int position, View convertView, ViewGroup parent) {
          TextView numberView;
  
          if (convertView == null){
              numberView = new TextView(context);
              numberView.setLayoutParams(new GridView.LayoutParams(80, 80));
              numberView.setPadding(8, 8, 8, 8);
              numberView.setTextColor(context.getResources().getColor(R.color.abc_background_cache_hint_selector_material_light));
          }
          else {
              numberView = (TextView) convertView;
          }
  
          numberView.setText(numeriGiocabili[position]);
          return numberView;
  
      }
  }
  </code></pre>