Problem mit Listview. Item nicht selektierbar

    <ListView
        android:id="@+id/habentable"
        android:layout_width="match_parent"
        android:layout_height="300dp"
        android:choiceMode="singleChoice"
        />

<TextView android:id="@+id/textViewDescription"
        android:layout_width="200dp"
        android:layout_height="fill_parent"
        android:gravity="center_vertical"
        android:textStyle="bold"
        android:textSize="14dp"
        android:textColor="#000000"
        android:layout_marginTop="2dp"
        android:layout_marginBottom="2dp"
        android:clickable="false"
        android:focusable="false"
        android:focusableInTouchMode="false" />

<TextView android:id="@+id/textViewValue"
        android:layout_width="120dp"
        android:layout_height="fill_parent"
        android:gravity="center_vertical"
        android:textStyle="bold"
        android:textSize="14dp"
        android:textColor="#000000"
        android:layout_marginTop="2dp"
        android:layout_marginBottom="2dp"        
        android:clickable="false"
        android:focusable="false"
        android:focusableInTouchMode="false" />

public class AccountDataAdapter extends ArrayAdapter<AccountData>{

    Context context;
    int layoutResourceId;   
    AccountData data[] = null;
   
    public AccountDataAdapter(Context context, int layoutResourceId, AccountData[] data) {
        super(context, layoutResourceId, data);
        try {
            this.layoutResourceId = layoutResourceId;
            this.context = context;
            this.data = data;
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        try {
            View row = convertView;
            AccountDataHolder holder = null;
      
            if(row == null)
            {
                LayoutInflater inflater = ((Activity)context).getLayoutInflater();
                row = inflater.inflate(layoutResourceId, parent, false);
               
                holder = new AccountDataHolder();
                holder.txtDescription = (TextView)row.findViewById(R.id.textViewDescription);
                holder.txtValue = (TextView)row.findViewById(R.id.textViewValue);
               
                row.setTag(holder);
            }
            else
            {
                holder = (AccountDataHolder)row.getTag();
            }
      
            AccountData accData = data[position];
            holder.txtDescription.setText(accData.getDescription());
            holder.txtValue.setText(Float.toString(accData.getPrice()));
      
            return row;
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return null;
        }
    }
   
    static class AccountDataHolder
    {
        TextView txtDescription;
        TextView txtValue;
    }
}

listView.setOnItemClickListener(new OnItemClickListener() {
	@Override
	public void onItemClick(AdapterView<?> av, View v, int index, long arg3) {
		...
		...
		...			
	}
});

import java.util.ArrayList;

import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

/*
 * Layout:
 *   main.xml enthält nur 1 ListView-Element:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent">
  
    <ListView android:layout_width="fill_parent" 
      android:layout_height="fill_parent" 
      android:id="@+id/mainListView">
    </ListView>
</LinearLayout>

 */
public class ListViewActivity extends Activity {
  
  private ListView mainListView ;
  private ArrayAdapter<String> listAdapter ;
  private ArrayList<String> modelList;
  String[] elemente = {"Mercury", "Venus", "Earth", "Mars"
                          ,"Jupiter", "Saturn" ,"Uranus", "Neptune"
                          ,"Ceres", "Pluto", "Haumea", "Makemake"
                          ,"Eris"
  };
  View previousItem=null;
  
  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    // Find the ListView resource.
    mainListView = (ListView) findViewById( R.id.mainListView );
    mainListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
      @Override
      public void onItemClick( AdapterView<?> parent, View item, 
                               int position, long id) {
          String tvw = listAdapter.getItem( position ); //Text der Listenzeile
          setBgColor(item); //aktuelle Zeile hervorheben
          Toast.makeText(getApplicationContext(), "**** "+tvw, Toast.LENGTH_SHORT).show();
      }
    });
    
    // Create and populate models.
    modelList = new ArrayList<String>();
    for (String element: elemente) {
        modelList.add(element);
    }
    
    // Set our custom array adapter as the ListView's adapter.
    listAdapter = new ArrayAdapter<String>( this,
//          von Android bereitgestellte Layouts
            android.R.layout.simple_list_item_1, android.R.id.text1, modelList);
    mainListView.setAdapter( listAdapter );
  }

  //angeklickte Zeile färben
  void setBgColor(View item) {
    if (previousItem != null) {
      previousItem.setBackgroundColor(Color.BLACK);
    }
    item.setBackgroundColor(Color.BLUE);
    previousItem =item;
  }
}

...    
habenList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick( AdapterView<?> parent, View item, 
                                         int position, long id) {
                    selectedHaben = adapterHaben.getItem( position ); 
                    setBgColor(item); 
                }
              });
...