You are accessing a null variable in line 111 in file MainActivity2.java . Check what you wrote there. From your code it seems that either labelDate is null or date is null. Verify you have values in them , you can also debug. In general, it seems best if you do some tutorial from developer.android.com … Read more
You should change this ((CheckedTextView) convertView).setText(parentItems.get(groupPosition)); ((CheckedTextView) convertView).setChecked(isExpanded); With if (convertView == null) { LayoutInflater infalInflater = (LayoutInflater)_context .getSystemService(Context.LAYOUT_INFLATER_SERVICE); convertView = infalInflater.inflate(R.layout.group_list, null); } TextView mGroupText = (TextView) convertView.findViewById(R.id.title); mGroupText.setText(parentItems.get(groupPosition)); CheckBox mCheckBox = (CheckBox) convertView.findViewById(R.id.cb); mCheckBox.setChecked(isExpanded); Your app crashed it’s because there no CheckedTextView in your group_list.xml layout file.