Remove multiple items in listView by checkBox using button

In listView, it contains checkbox. When delete button is clicked, it will delete the list which the checkbox is checked. I refer to this answer.

Adapter class

public class DeleteAdapter extends BaseAdapter {

    private static ArrayList<SearchList> search;
    private LayoutInflater mInflater;
    ListView listview;
    Button delete; // button get from DeleteTask class
    int checkBoxCounter = 0;

    public DeleteAdapter(Context context, ArrayList<SearchList> searchList, ListView listview,Button delete) {
        search=searchList;
        this.delete=delete;
        this.listview=listview;
        mInflater = LayoutInflater.from(context);
        delete.setText("DELETE");

    }
    public int getCount() {
        return search.size();
    }

    public SearchList getItem(int position) {
        return search.get(position);
    }

    public long getItemId(int position) {
        return 0;
    }

    public void removeItem(int position) {
        search.remove(position);
        this.notifyDataSetChanged();
    }

    public View getView(final int position, View convertView, ViewGroup parent) {
        ViewHolder holder = null;
        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.delete_task_with_edittext, null);
            holder = new ViewHolder();
            holder.text = (TextView) convertView.findViewById(R.id.task_title);
            holder.time = (TextView) convertView.findViewById(R.id.time);
            holder.date = (TextView) convertView.findViewById(R.id.date);
            holder.ckbox = (CheckBox) convertView.findViewById(R.id.checkBox);

            holder.ckbox.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if (((CheckBox) v).isChecked()) {
                        int getPosition = (Integer) v.getTag();  // Here we get the position that we have set for the checkbox using setTag.
                        search.get(getPosition).setSelected(((CheckBox)v).isChecked()); // Set the value of checkbox to maintain its state.
                        checkBoxCounter ++;
                        delete.setText("DELETE"+""+"("+ checkBoxCounter +")");
                    } else
                    {
                        int getPosition = (Integer) v.getTag();  // Here we get the position that we have set for the checkbox using setTag.
                        search.get(getPosition).setSelected(((CheckBox) v).isChecked()); // Set the value of checkbox to maintain its state.
                        checkBoxCounter--;
                        if (checkBoxCounter == 0) {
                            delete.setText("DELETE");
                        }
                        else {
                            delete.setText("DELETE" + "" + "(" + checkBoxCounter + ")");
                        }
                    }
                }
            });
            convertView.setTag(holder);

            delete.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {

                    SparseBooleanArray checkedItemPositions = listview.getCheckedItemPositions();
                    int itemCount = listview.getCount();

                    for(int i=0; i <itemCount; i++){
                        if(checkedItemPositions.get(i)){
                            removeItem(i);
                            --i;
                        }
                    }
                    checkedItemPositions.clear();
                    //DeleteAdapter.notifyDataSetChanged();
                }
            });

        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        holder.ckbox.setTag(position);
        holder.text.setText(search.get(position).getTitle());
        holder.time.setText(search.get(position).getTime());
        holder.date.setText(search.get(position).getDate());
        holder.ckbox.setChecked(search.get(position).isSelected());
        return convertView;

    }

    static class ViewHolder {
        TextView text,time,date;
        CheckBox ckbox;

    }
}

When I click the delete button, I get nullpointerexception error.

java.lang.NullPointerException
            at com.example.seng.healthyapp.adapter.DeleteAdapter$2.onClick(DeleteAdapter.java:107)
            at android.view.View.performClick(View.java:4230)
            at android.view.View$PerformClick.run(View.java:17660)
            at android.os.Handler.handleCallback(Handler.java:800)
            at android.os.Handler.dispatchMessage(Handler.java:100)
            at android.os.Looper.loop(Looper.java:194)
            at android.app.ActivityThread.main(ActivityThread.java:5433)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:525)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:924)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:691)
            at dalvik.system.NativeStart.main(Native Method)

Refer to

   if(checkedItemPositions.get(i)){