Как получить значения из ArrayAdapter в MainActivity для настраиваемого ListView?

Question

Я хотел бы получить значение ArrayAdapter для MainActivity для Custom ListView с CheckBoxes. Но всякий раз, когда я пытался получить какое-либо значение из основного действия, приложение вылетает.в то время как спасибо. Вот мой код

public class ModelListViewActivity extends ListActivity {  
public static final String KK_TAG="KK AHH!!!";
MyCustomArrayAdapter mas;
public void onCreate(Bundle icicle)
{        
    super.onCreate(icicle); 
    setContentView(R.layout.main);     
    ArrayAdapter<Model> adapter = new MyCustomArrayAdapter(this,getModel());    
    setListAdapter(adapter);      

} 

private List<Model> getModel() 
{         
    List<Model> list = new ArrayList<Model>();      
    list.add(get("Android +200","Google"));    
    list.add(get("Windows +500","Microsoft"));         
    list.add(get("iPhone +600","Apple"));        
    list.add(get("Ubuntu +700","Linux")); 
    list.add(get("Bada -800","Samsung"));      
    list.add(get("Android +1000","Google"));     
    list.add(get("Symbian -1000","Nokia"));      
    list.add(get("Windows XP +400","Microsoft"));

    // select one item by default 
    return list;   
    } 
private Model get(String s,String place) 
{      
    return new Model(s,place);
} 

}

Вот адаптер, и в этом я хочу получить выбранную строку в основном действии

 public class MyCustomArrayAdapter extends ArrayAdapter<Model> 
{ 
    public static final String KK_TAG="KK AHH!!!";
    String selected = "Karthik";
    private final List<Model> list; 
    private final Activity context; 
    public MyCustomArrayAdapter(Activity context, List<Model> list) {
        super(context, R.layout.list_layout, list); 
        this.context = context; 
        this.list = list;     
        } 
    static class ViewHolder
    {    
        protected TextView text, sub; 
        protected CheckBox checkbox; 
    }    
    public void manipulation()
    {
        int valued=0;
        selected = selected.replaceAll("\\s+", " ");
        Log.v(KK_TAG,"selected:" +selected);
        Pattern p = Pattern.compile("-?\\d+"); 
        Matcher m = p.matcher(selected); 
        while (m.find()) 
        {  
            Log.v(KK_TAG,m.group());
            String test=m.group();
            int aInt = Integer.parseInt(test);
            valued=valued+aInt;

        } 
        String conv=Integer.toString(valued);
        Log.v(KK_TAG, "Conv: "+conv);


    }




    public void tester()
    {
        Log.v(KK_TAG, "Conv: ");
    }
    @Override    
    public View getView(int position, View convertView, ViewGroup parent) 
    { 
        View view = null; 
        if (convertView == null) {
            LayoutInflater inflator = context.getLayoutInflater(); 
            view = inflator.inflate(R.layout.list_layout, null); 
            final ViewHolder viewHolder = new ViewHolder(); 
            viewHolder.text = (TextView) view.findViewById(R.id.label); 
            viewHolder.text.setTextColor(Color.BLACK);
            viewHolder.sub = (TextView) view.findViewById(R.id.sub); 
            viewHolder.sub.setTextColor(Color.GRAY); 
            viewHolder.checkbox = (CheckBox) view.findViewById(R.id.check);
            viewHolder.checkbox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() { 
                @Override
                public void onCheckedChanged(CompoundButton buttonView,boolean isChecked)
                { 
                    Model element = (Model) viewHolder.checkbox.getTag();
                    element.setSelected(buttonView.isChecked()); 
                    Log.v(KK_TAG, "Checked : " + element.getName());

                    if(isChecked)
                    {
                        selected +=element.getName()+" ";
                        Log.v(KK_TAG, "Checked : " + selected);

                    }
                    else
                    {
                        String source = selected;
                        String find = element.getName();
                        String replace = "";
                        Pattern pattern = Pattern.compile(find);
                        Matcher matcher = pattern.matcher(source);
                        selected = matcher.replaceAll(replace);
                        Log.v(KK_TAG,"Source = " + source);
                        Log.v(KK_TAG,"UnChecked = " + selected);

                    }

                }  }); 
            view.setTag(viewHolder);
            viewHolder.checkbox.setTag(list.get(position));
            } else 
            { 
                view = convertView;
                ((ViewHolder) view.getTag()).checkbox.setTag(list.get(position)); 
                } 
        ViewHolder holder = (ViewHolder) view.getTag();
        holder.text.setText(list.get(position).getName()); 
        holder.sub.setText(list.get(position).getPlace()); 
        holder.checkbox.setChecked(list.get(position).isSelected());    
        return view; 
}
}