Question

I’ve created a ListView that in each row has a button with UP and DOWN arrow. Pressing these buttons makes the row to be shifted one position up or down.

I’ve achieved it by implementing OnClickListener for both buttons in a the override method getView. It works as it should however I fill bad with that cuz it seems to be highly memory consuming and lots of code is doubled.

@Override
public View getView(final int position, View convertView, ViewGroup parent) {

    View rowView = inflater.inflate(R.layout.row_layout, parent, false);

    TextView textView = (TextView) rowView.findViewById(R.id.label);
    CheckBox checkBox = (CheckBox) rowView.findViewById(R.id.checkbox);
    checkBoxes.add(position, checkBox);

    String address = this.getItem(position).getAddress();
    String tokenizedAddress = tokenizeAddress(address);

    textView.setText(tokenizedAddress);

    ImageButton buttonUp = (ImageButton)rowView.findViewById(R.id.button_up);
    ImageButton buttonDown = (ImageButton)rowView.findViewById(R.id.button_down);

    buttonUp.setOnClickListener(new OnClickListener() {

        public void onClick(View v) {
            ListAdapter adapter = ListAdapter.this;

            if(position != 0 ){
                GameTask current = adapter.getItem(position);

                ArrayList<GameTask> list = new ArrayList<GameTask>();
                for( int i = 0; i < adapter.getCount(); i++ )
                    list.add(adapter.getItem(i));
                list.remove(position);
                list.add(position-1, current);
                adapter.clear();
                for( int i = 0; i < list.size(); i++ ){
                    adapter.add(list.get(i));
                }
                adapter.notifyDataSetChanged();
            }

        }
    });

    buttonDown.setOnClickListener(new OnClickListener() {

        public void onClick(View v) {
            ListAdapter adapter = ListAdapter.this;

            if(position != adapter.getCount()-1 ){
                GameTask current = adapter.getItem(position);

                ArrayList<GameTask> list = new ArrayList<GameTask>();
                for( int i = 0; i < adapter.getCount(); i++ )
                    list.add(adapter.getItem(i));
                list.remove(position);
                list.add(position+1, current);
                adapter.clear();
                for( int i = 0; i < list.size(); i++ ){
                    adapter.add(list.get(i));
                }
                adapter.notifyDataSetChanged();
            }

        }
    });


    return rowView;
}

Both listeners do almost the same, the only difference is the condition and the value of shifting +1/-1. I was wondering about creating the inner class implementing OnClickListener in the extended ArrayAdapter class however, I have no idea, how I could then pass the position of the row clicked to this inner class.

Answer 1

Instead of adding and removing elements from your ArrayList, you can better implement Collections.swap(List list, int firstElementIndex, int secondElementIndex) it would be much easier as you don’t have to iterate through the whole Collection. A simple example for the same can be found here.