Android GridView reorder elements via Drag and Drop

Question

I have a GridView in an application I am working on. I would like to be able to reorder the items in the GridView via drag-and-drop. I have found lots of help for ListViews but nothing on GridViews. I want to achieve behaviour like in this launcher app http://www.youtube.com/watch?v=u5LISE8BU_E&t=5m30s. Any ideas?

Answer 1

If you don't resolve this problem I will provide my code. But it works on Android 3.0 and above, because I use android drag-n-drop framework

grid = (GridView) findViewById(R.id.grid);
grid.setAdapter(new DragGridAdapter(items, getActivity()));

....

grid.setOnTouchListener(new View.OnTouchListener() {

        @Override
        public boolean onTouch(View v, MotionEvent event) {

            if (event.getAction() == MotionEvent.ACTION_DOWN) {
                GridView parent = (GridView) v;

                int x = (int) event.getX();
                int y = (int) event.getY();

                int position = parent.pointToPosition(x, y);
                if (position > AdapterView.INVALID_POSITION) {

                    int count = parent.getChildCount();
                    for (int i = 0; i < count; i++) {
                        View curr = parent.getChildAt(i);
                        curr.setOnDragListener(new View.OnDragListener() {

                            @Override
                            public boolean onDrag(View v, DragEvent event) {

                                boolean result = true;
                                int action = event.getAction();
                                switch (action) {
                                case DragEvent.ACTION_DRAG_STARTED:
                                    break;
                                case DragEvent.ACTION_DRAG_LOCATION:
                                    break;
                                case DragEvent.ACTION_DRAG_ENTERED:
                                    v.setBackgroundResource(R.drawable.shape_image_view_small_gallery_selected);
                                    break;
                                case DragEvent.ACTION_DRAG_EXITED:
                                    v.setBackgroundResource(R.drawable.shape_image_view_small_gallery_unselected);
                                    break;
                                case DragEvent.ACTION_DROP:
                                    if (event.getLocalState() == v) {
                                        result = false;
                                    } else {
                                        View droped = (View) event.getLocalState();
                                        GridItem dropItem = ((DragGridItemHolder) droped.getTag()).item;

                                        GridView parent = (GridView) droped.getParent();
                                        DragGridAdapter adapter = (DragGridAdapter) parent.getAdapter();
                                        List<GridItem> items = adapter.getItems();

                                        View target = v;
                                        GridItem targetItem = ((DragGridItemHolder) target.getTag()).item;
                                        int index = items.indexOf(targetItem);
                                        items.remove(dropItem);
                                        items.add(index, dropItem);
                                        adapter.notifyDataSetChanged();
                                    }
                                    break;
                                case DragEvent.ACTION_DRAG_ENDED:
                                    v.setBackgroundResource(R.drawable.shape_image_view_small_gallery_unselected);
                                    break;
                                default:
                                    result = false;
                                    break;
                                }
                                return result;
                            }
                        });
                    }

                    int relativePosition = position - parent.getFirstVisiblePosition();


                    View target = (View) parent.getChildAt(relativePosition);

                    DragGridItemHolder holder = (DragGridItemHolder) target.getTag();
                    GridItem currentItem = holder.item;
                    String text = currentItem.getFile().getAbsolutePath();

                    ClipData data = ClipData.newPlainText("DragData", text);
                    target.startDrag(data, new View.DragShadowBuilder(target), target, 0);
                }
            }
            return false;

and DragGridAdapter

public class DragGridAdapter extends BaseAdapter{
private Context context;
private List<GridItem> items;

public DragGridAdapter(List<GridItem> items, Context context){
    this.context = context;
    this.items = items;
}

@Override
public int getCount() {
    return items.size();
}

@Override
public Object getItem(int position) {
    return items.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    DragGridItemHolder holder;
    if (convertView == null) {
        holder = new DragGridItemHolder();

        ImageView img = new ImageView(context);
        holder.image = img;
        convertView = img;
        convertView.setTag(holder);
    } else {
        holder = (DragGridItemHolder) convertView.getTag();
    }
    holder.item = items.get(position);
    holder.image.setImageBitmap(items.get(position).getBitmap());
    return convertView;
}

public List<GridItem> getItems() {
    return items;
}

I hope it helps to you