Android : Why won't android simple listview display data?

I can't get a simple listview to display data. I know the listview is getting the data because empty listitems are displayed according to the number of data elements given to the arrayadapter. I am attempting to show the list in a alert dialog so maybe thats causing the problem. I don't know. Can anyone help me?

public class FileExplorer extends DialogFragment {
private AlertDialog.Builder builder;
private List<File> files;
private List<String>fileList;
private FileIO fIO;
ListActivity listActivity;
ListView lv;
ArrayAdapter<String> arrayAdapter;

Button btnFileNavigatorBack;

public FileExplorer(){

}

@Override
public Dialog onCreateDialog(Bundle savedInstanceState){
    fIO = new FileIO();
    fileList = new ArrayList<String>();
    files = fIO.getDirectoryContents(null);
    for(File f : files){
        fileList.add(f.getName());
    }

    LayoutInflater inflater = getActivity().getLayoutInflater();
    View view = inflater.inflate(R.layout.dialog_file, (ViewGroup)getActivity().getCurrentFocus());

    lv = (ListView)view.findViewById(R.id.lvFileExplorer);
    arrayAdapter = new ArrayAdapter<String>(getActivity().getApplicationContext(), android.R.layout.simple_expandable_list_item_1,
            fileList);

    builder = new AlertDialog.Builder(getActivity());
    builder.setView(view)
            .setPositiveButton(R.string.dialog_button_ok, new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {

                }
            })
            .setNegativeButton(R.string.dialog_button_cancel, new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {

                }
            });

    btnFileNavigatorBack = (Button)view.findViewById(R.id.btnFileNavigatorBack);
    btnFileNavigatorBack.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Toast.makeText(getActivity().getApplicationContext(), ":D", Toast.LENGTH_LONG).show();
        }
    });

    Dialog dialog = builder.create();
    dialog.show();
    lv.setAdapter(arrayAdapter);

    return dialog;
}

}

XML file for listview

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="match_parent">

<LinearLayout
    android:orientation="horizontal"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">

</LinearLayout>

<GridLayout
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:columnCount="2"
    android:rowCount="2">

    <Button
        style="?android:attr/buttonStyleSmall"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="New Button"
        android:id="@+id/btnFileNavigatorBack"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="Medium Text"
        android:id="@+id/textView6"
        android:layout_marginLeft="125dp" />

    <ListView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/lvFileExplorer"
        android:layout_columnSpan="2" />
</GridLayout>

I'm new to android programming. Coding for listview seems like it should be intuitive but I can't make sense of this.