How to set checkbox value in a BaseAdapter class in Android

I have listview in that i am inflating a Layout that will have checkbox like this

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

    <CheckBox
        android:id="@+id/checkBox"
        android:text=""
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
</LinearLayout>

Now from the main Activity i am calling a Adapter class

 public  void setData(){
        dataList = new ArrayList<String>();
        Adapterclass = new MAdapter(this);
        for (int i = 0; i < data.length; i++) {
            Adapterclass .addItem(str[i]);
            dataList .add(str[i]);
        }
        listview.setAdapter(Adapterclass);
    }

Base Adapter Class

 public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder = null;
        CheckBox cb;
        if (convertView == null) {
            holder = new ViewHolder();
            convertView = mInflater.inflate(R.layout.main, parent, false);
            cb = (CheckBox) convertView.findViewById(R.id.checkbox);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        String str = mData.get(position);
       return convertView;
    }

I want to set the value of the checkbox i.e cb in the adapter class how can we do this .Please help me in this