trying to display data from my table into listview in android whats wrong?

as I mentioned in the title

I am trying to display data from my table into listview but when I open the emulator it stops immediately and I think i have an error nullpointer or something like that .. or I do not really now ..

here is my code:

JAVA

MainActivity.java :

public class MainActivity extends Activity {

ListView PersonsList;
DataBaseAdapter  helper;
private SimpleCursorAdapter dataAdapter;



@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    helper = new DataBaseAdapter(this);

    displayListView();

}


@TargetApi(Build.VERSION_CODES.HONEYCOMB)


private void displayListView() {


    Cursor cursor = helper.fetchAllPersons();

    // The desired columns to be bound
    String[] columns = new String[]{

            DataBaseAdapter.Helper.PERSON_NAME,
            DataBaseAdapter.Helper.GENDER,
    };

    // the XML defined views which the data will be bound to
    int[] to = new int[]{
            R.id.personName,
            R.id.personGender,

    };

    // create the adapter using the cursor pointing to the desired data
    //as well as the layout information
    dataAdapter = new SimpleCursorAdapter(
            this, R.layout.single_person_item,
            cursor,
            columns,
            to,
            0);

    PersonsList = (ListView) findViewById(R.id.personsListView);
    PersonsList.setAdapter(dataAdapter);
 }
 }

fetcAllPpersons() in DataBaseAdapter.java :

public Cursor fetchAllPersons() {

    SQLiteDatabase db = helper.getWritableDatabase();

    Cursor mCursor = db.query(Helper.PERSONS_TABLE, new String[]     {Helper.PERSON_ID,Helper.PERSON_NAME,Helper.DATE_OF_BIRTH,Helper.GENDER,Helper.ADDRESS},
            null, null, null, null, null);

    if (mCursor != null) {
        mCursor.moveToFirst();
    }
    return mCursor;
}

---

xml:

activity_main.xml:

<RelativeLayout xmlns:android="http://ift.tt/nIICcg"
 xmlns:tools="http://ift.tt/LrGmb4"      android:layout_width="match_parent"
android:layout_height="match_parent"    android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity"
>


<Button
    android:layout_width="200dp"
    android:layout_height="wrap_content"
    android:text="+"
    android:id="@+id/addnewperson"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Delete All"
    android:id="@+id/deleteall"
    android:layout_alignParentBottom="true"
    android:layout_alignRight="@+id/addnewperson"
    android:layout_alignEnd="@+id/addnewperson" />

<ScrollView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/scrollView2"
    android:layout_below="@+id/addnewperson"
    android:layout_alignLeft="@+id/addnewperson"
    android:layout_alignStart="@+id/addnewperson">


</ScrollView>

<ListView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/personsListView"
    android:layout_below="@+id/scrollView2"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />


 </RelativeLayout>

where PERSONS_TABLE is the table i want to show some infromation from

where is the problem ??

thx in advance