Android ใช้งาน Listview+button มีปัญหาครับ เมื่อคลิกปุ่มมีปัญหากับ setEnable ของปุ่ม

public class MainActivity extends AppCompatActivity {

    private ArrayList<String> data = new ArrayList<String>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ListView lv = (ListView) findViewById(R.id.listview);
        generateListContent();
        lv.setAdapter(new MyListAdaper(this, R.layout.list_item, data));
        lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Toast.makeText(MainActivity.this, "List item was clicked at " + position, Toast.LENGTH_SHORT).show();
            }
        });
    }

    private void generateListContent() {
        for(int i = 0; i < 55; i++) {
            data.add("This is row number " + i);
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    private class MyListAdaper extends ArrayAdapter<String> {
        private int layout;
        private List<String> mObjects;
        private MyListAdaper(Context context, int resource, List<String> objects) {
            super(context, resource, objects);
            mObjects = objects;
            layout = resource;
        }

        @Override
        public View getView(final int position, View convertView, ViewGroup parent) {
            ViewHolder mainViewholder = null;
            if(convertView == null) {
                LayoutInflater inflater = LayoutInflater.from(getContext());
                convertView = inflater.inflate(layout, parent, false);
                ViewHolder viewHolder = new ViewHolder();
                viewHolder.thumbnail = (ImageView) convertView.findViewById(R.id.list_item_thumbnail);
                viewHolder.title = (TextView) convertView.findViewById(R.id.list_item_text);
                viewHolder.button = (Button) convertView.findViewById(R.id.list_item_btn);
                convertView.setTag(viewHolder);
            }
            mainViewholder = (ViewHolder) convertView.getTag();
            final ViewHolder finalMainViewholder = mainViewholder;
            mainViewholder.button.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Toast.makeText(getContext(), "Button was clicked for list item " + position, Toast.LENGTH_SHORT).show();
                finalMainViewholder.button.setEnabled(false);
                }
            });
            mainViewholder.title.setText(getItem(position));

            return convertView;
        }
    }
    public class ViewHolder {

        ImageView thumbnail;
        TextView title;
        Button button;
    }
}