android layout not displayed

I have trouble displaying the layout of my main activity :

I create an ActivityA with an ImageView.

In onCreate(), I launch an AsyncTask, which retrieves content from Internet, and opens an ActivityB.

When I launch my application, it displays ActivityB right away.

public class ActivityA extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        MyTask mytask = new MyTask();
        mytask.execute();

    }

}

My MainActivity xml file is the following :

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://ift.tt/nIICcg"
    android:id="@+id/loadingPanel"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <ImageView
        android:id="@+id/home_page"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:src="@drawable/ic_home_page" />

    <ProgressBar
        android:id="@+id/marker_progress"
        style="?android:attr/progressBarStyle"
        android:layout_width="50dp"
        android:layout_height="50dp"
        android:layout_gravity="center_vertical|center_horizontal"
        android:indeterminate="true" />

</RelativeLayout>

The ProgressBar is used to show the loading process of the AsyncTask.

thanks for helping