title: android:background don't work except for overview
body: <p>I work on an Android application, and I just try to put a background on an empty activity by way of welcome in the application. In the overview of the xml file, the image is displayed, but when i try the app on the emulator or on my phone, she's not displayed. They have no error, I don't understand. Can someone help me please ?</p>
  
  <pre><code>public class MainActivity extends Activity {
  
  private SQLiteDatabase db;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
  
      Intent i = new Intent(this, ListeContact.class);
      try
      {
          Thread.sleep(3000);
      }
      catch (InterruptedException e)
      {
          e.printStackTrace();
      }
      startActivity(i);
      this.finish();
  }
  }
  </code></pre>
  
  <p>activity_main.xml : </p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:background="@drawable/fond"&gt;
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>P.S. My image named fond.png is on 5 folder named drawable-hdpi, drawable-ldpi, drawable-mdpi, drawable-xdpi and drawable-xxdpi.</p>