Question

I have a button that should sort a ListView using a custom adapter. The button listener is as follows:

collectionSort.setOnClickListener(new OnClickListener() {
    public void onClick(View v) {
        sortOrder = -sortOrder;
        Log.d("DBGINF", "Sort Order: " + sortOrder);
        m.sortByTitles(sortOrder);
        m.notifyDataSetChanged();
});

The sort order changes as it should, and the data in the array is sorted, the actual view is never updated by the notifyDataSetChanged though. Here’s the sortByTitles() method:

public void sortByTitles(int dir) {
    if (dir > 0) {
        sort(new StringComparator());
    } else if (dir < 0) {
        sort(new ReverseStringComparator());
    }
    Log.d("Data Set: ", this.getItem(0) + "");
}

The notifyDataSetChanged() doesn’t ever update the view inside an OnClickListener, but always works properly outside one of the OnClickListeners. What am I doing wrong?

EDIT

Here is the constructor in the Adapter class:

public MainMenuArrayAdapter(Context context, CollectionObject[] objects) {
    super(context, R.layout.mainmenurow, objects);
    myContext = context;
}

And here’s how it gets initialized in the onCreate() method of the Activity:

CollectionObject[] sample = new CollectionObject[] { c1, c2, c3, c4, c5, c6 };
final MainMenuArrayAdapter m = new MainMenuArrayAdapter(this, sample);

Where c1 – c6 are just some temporary CollectionObjects for testing.

Answer 1

What kind of adapter are you extending? I think you are actually sorting a copy of the items in your adapter. Are you setting myCollections in the adapter again? Btw if you extend ArrayAdapter keep in mind that the adapter itself has a sort method which accept your own comparator.

EDIT:
I wrote a super stupid example with a custom adapter and sorting, you can press menu for sorting items. Hope it will help!

public class SortActivity extends ListActivity {

private StupidAdapter stupidAdapter;
private List<String> list = new ArrayList<String>();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    list.add("Android-a");
    list.add("Android-b");
    list.add("Android-c");
    list.add("BlackBerry-a");
    list.add("BlackBerry-b");
    list.add("BlackBerry-c");
    list.add("Windows-a");
    list.add("Windows-b");
    list.add("Windows-c");

    // keep in mind that from now on whatever changes you do on list is not reflected on the adapter.
    // the array adapter keeps its own internal data
    stupidAdapter = new StupidAdapter(this, list);
    setListAdapter(stupidAdapter);

}

@Override
public boolean onCreateOptionsMenu(final Menu menu) {
    new MenuInflater(this.getApplication()).inflate(R.menu.main_menu, menu);
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(final MenuItem item) {
    final int id = item.getItemId();
    if (id == R.id.menu_main_sort_az) {
        stupidAdapter.sort(new Comparator<String>() {
            public int compare(String object1, String object2) {
                return object1.compareTo(object2);
            };
        });
    } else if (id == R.id.menu_main_sort_za) {
        stupidAdapter.sort(new Comparator<String>() {
            public int compare(String object1, String object2) {
                return object2.compareTo(object1);
            };
        });
    }
    stupidAdapter.notifyDataSetChanged();
    return true;
}

class StupidAdapter extends ArrayAdapter<String> {

    public StupidAdapter(Context context, List<String> list) {
        super(context, R.layout.list_item, list);
    }

    @Override
    public View getView(final int position, View row, final ViewGroup parent) {
        ViewHolder viewHolder;

        final String item = getItem(position);

        if (row == null) {
            row = getLayoutInflater().inflate(R.layout.list_item, parent, false);
            viewHolder = new ViewHolder(row);

            row.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) row.getTag();
        }

        viewHolder.refreshData(item);

        return row;
    }       

    class ViewHolder {
        TextView title;
        public ViewHolder(View row) {
            this.title = (TextView) row.findViewById(R.id.title);
        }
        public void refreshData(final String text) {
            this.title.setText(text);
        }
    }   

}

}

list_item.xml

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:background="#ffffffff">

<TextView 
    android:id="@+id/title"
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:textSize="15sp"
    android:textColor="#ff000000"/>

 </LinearLayout>         

main_menu.xml (under res/menu)

<menu xmlns:android="http://schemas.android.com/apk/res/android">   
    <item android:id="@+id/menu_main_sort_az" android:title="Sort A-Z"/>
    <item android:id="@+id/menu_main_sort_za" android:title="Sort Z-A"/>
</menu>