ListView not refreshing already-visible items

Question

I\'m displaying a list of contacts (name + picture) using the ListView. In order to make the initial load fast, I only load the names first, and defer picture l

Answer 1

Here I go answering my own question with a hackaround that I've settled on. Apparently, notifyDataSetChanged() is only to be used if you are adding / removing items. If you are updating information about items that are already displayed, you might end up with visible items not updating their visual appearance (getView() not being called on your adapter).

Furthermore, calling invalidateViews() on the ListView doesn't seem to work as advertised. I still get the same glitchy behavior with getView() not being called to update on-screen items.

At first I thought the issue was caused by the frequency at which I called notifyDataSetChanged() / invalidateViews() (very fast, due to updates coming from different sources). So I've tried throttling calls to these methods, but still to no avail.

I'm still not 100% sure this is the platform's fault, but the fact that my hackaround works seems to suggest so. So, without further ado, my hackaround consists in extending the ListView to refresh visible items. Note that this only works if you're properly using the convertView in your adapter and never returning a new View when a convertView was passed. For obvious reasons:

public class ProperListView extends ListView {

    private static final String TAG = ProperListView.class.getName();

    @SuppressWarnings("unused")
    public ProperListView(Context context) {
        super(context);
    }

    @SuppressWarnings("unused")
    public ProperListView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @SuppressWarnings("unused")
    public ProperListView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    class AdapterDataSetObserver extends DataSetObserver {
        @Override
        public void onChanged() {
            super.onChanged();

            refreshVisibleViews();
        }

        @Override
        public void onInvalidated() {
            super.onInvalidated();

            refreshVisibleViews();
        }
    }

    private DataSetObserver mDataSetObserver = new AdapterDataSetObserver();
    private Adapter mAdapter;

    @Override
    public void setAdapter(ListAdapter adapter) {
        super.setAdapter(adapter);

        if (mAdapter != null) {
            mAdapter.unregisterDataSetObserver(mDataSetObserver);
        }
        mAdapter = adapter;

        mAdapter.registerDataSetObserver(mDataSetObserver);
    }

    void refreshVisibleViews() {
        if (mAdapter != null) {
            for (int i = getFirstVisiblePosition(); i <= getLastVisiblePosition(); i ++) {
                final int dataPosition = i - getHeaderViewsCount();
                final int childPosition = i - getFirstVisiblePosition();
                if (dataPosition >= 0 && dataPosition < mAdapter.getCount()
                        && getChildAt(childPosition) != null) {
                    Log.v(TAG, "Refreshing view (data=" + dataPosition + ",child=" + childPosition + ")");
                    mAdapter.getView(dataPosition, getChildAt(childPosition), this);
                }
            }
        }
    }

}