Android Multiple CheckBoxes cliked

I have a RecyclerView and I have created an adapter RecyclerView.Adapter for it. My RecyclerView Item contains one TextView, one Checkbox. If the user clicks the checkbox I show a cross through the text. But when I click one checkbox, some other checkboxes are also clicked. My BindView Code

 public void onBindViewHolder(Tasks_View_Holder holder, int position) {
        final Tasks_View_Holder holder_final = holder;
        final int position_final = position;

        Tasks task = list.get(position);//list is my recyclerview
        holder.checkBox.setChecked(task.getChecked());
        if (holder.checkBox.isChecked()) {
            holder.taskname.setPaintFlags(holder.taskname.getPaintFlags() | Paint.STRIKE_THRU_TEXT_FLAG);
        } else {
            holder.taskname.setPaintFlags(0);

        }
        holder.taskname.setText(task.getTaskname());

        holder.checkBox.setOnCheckedChangeListener(new OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                Log.d("bhaskar", "on check changed checkbox" + position_final);
                Tasks task = list.get(position_final);
                task.setChecked(isChecked);
                list.set(position_final, task);
                if (isChecked) {

                    holder_final.taskname.setPaintFlags(holder_final.taskname.getPaintFlags() | Paint.STRIKE_THRU_TEXT_FLAG);
                } else {

                    holder_final.taskname.setPaintFlags(0);
                }
                updateTask(task.getTasknumber(), task.getTaskname(), task.getChecked());// a method that updates the task in internal database
                Handler handler = new Handler();

                final Runnable r = new Runnable() {
                    public void run() {
                        Log.d("bhaskar", "notify data item changed checkbox" + position_final);
                        notifyItemChanged(position_final);
                    }
                };

                handler.post(r);
            }
        });

    }