Android, How do i Update the selected item in my listview from my database?

Heres my code so far but the application crash when i press the update button can anyone help me im just new to android.

I want to update a selected item in my list i have already created the update activity that will allow me to load the values on my database but i cant figure out how to load the value of selected item in list.

{

    ArrayAdapter<String> ard=new ArrayAdapter<String> (this,android.R.layout.simple_list_item_single_choice,list);
    lv.setAdapter(ard);
    lv.setChoiceMode(ListView.CHOICE_MODE_SINGLE);

      btnupdate.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {

            SparseBooleanArray sba = lv.getCheckedItemPositions();
            Intent intent = new Intent(HomeworkInfo.this, UpdateHomework.class);
            startActivity(intent);
            finish();

        }



});

}