Android - Is ViewHolder pattern automatically implemented in CursorAdapter?

android, android-cursoradapter, database

Solution

My question is - does CursorAdapter re-uses views by internally implementing the ViewHolder pattern or it needs to be coded as we normally do in custom ArrayAdapter?

I'm not sure at what do you refer by the `ViewHolder` pattern. If you are referring to having a helper class to cache looking for view each time(and setting it as a tag for the row `View`) then the answer is no. If you want to implement this pattern you'll need to setup the holder(look for the views in the row view with `findViewById`) in the `newView` method and then set it as the tag for the row view. Then in the `bindView` method you can call `getTag`, retrieve the holder and use it. An example:

// custom CursorAdapter ...

    @Override
    public View newView(Context context, Cursor cursor, ViewGroup parent) {
        View rowView = ((LayoutInflater) context
                .getSystemService("layout_inflater")).inflate(
                R.layout.row_layout, parent, false);
        ViewHolder holder = new ViewHolder();
        holder.v1 = rowView.findViewById(R.id.v1);
        holder.v2 = rowView.findViewById(R.id.v2);
        rowView.setTag(holder);
        return rowView;
    }

    @Override
    public void bindView(View view, Context context, Cursor cursor) {
        ViewHolder holder = (ViewHolder) view.getTag();
        // use the holder filled with views
        // hlder.v1.setSomething
    }

    class ViewHolder {
        View v1, v2;
    }
// ...

If you are referring to the `convertView` being reused(like in non `Cursor` based adapters) then the answer is yes, the `getView` method implements this pattern, you just need to implement the `newView` and `bindView` methods and you're guaranteed to get a view which was recycled(if possible at that moment).

Problem

I always use `ViewHolder` pattern in my custom `ArrayAdapter` classes. However, in `CursorAdapter` the `getView()` method is not mandatory required to be overridden , but has the `bindView` and `newView` methods. My question is - does `CursorAdapter` re-uses views by internally implementing the `ViewHolder` pattern or it needs to be coded as we normally do in custom `ArrayAdapter`? If it needs to be coded, what is the correct way to do it? Update I'm using `android.support.v4.widget.CursorAdapter`

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