BaseAdapter.notifyDatasetChanged() not updating the ListView

Question

why does my listview not update when I call notifyDatasetChanged() ? the only way I can make it display the data is, to call setAdatper() on the ListView again... i also tried to call it via runOnUIThread() which did not change anything

The Adapter

/**
 * Adapter to provide the data for the online scores
 * 
 * @author soh#zolex
 *
 */
public class OnlineScoresAdapter extends BaseAdapter {

    private Context context;
    private List<ScoreItem> scores = new ArrayList<ScoreItem>();

    /**
     * Constructor
     * 
     * @param Context context
     */
    public OnlineScoresAdapter(Context context) {

        this.context = context;
    }

    /**
     * Add an item to the adapter
     * 
     * @param item
     */
    public void addItem(ScoreItem item) {

        this.scores.add(item);
    }

    /**
     * Get the number of scores
     * 
     * @return int
     */
    public int getCount() {

        return this.scores.size();
    }

    /**
     * Get a score item
     * 
     * @param int pos
     * @return Object
     */
    public Object getItem(int pos) {

        return this.scores.get(pos);
    }

    /**
     * Get the id of a score
     * 
     * @param in pos
     * @retrn long
     */
    public long getItemId(int pos) {

        return 0;
    }

    /**
     * Get the type of an item view
     * 
     * @param int pos
     * @return int
     */
    public int getItemViewType(int arg0) {

        return arg0;
    }

    /**
     * Create the view for a single list item.
     * Load it from an xml layout.
     * 
     * @param int pos
     * @param View view
     * @param ViewGroup viewGroup
     * @return View
     */
    public View getView(int pos, View view, ViewGroup group) {

        LinearLayout layout;
        if (view == null) {

            layout = (LinearLayout)View.inflate(this.context, R.layout.scoreitem, null);

        } else {

            layout = (LinearLayout)view;
        }

        TextView position = (TextView)layout.findViewById(R.id.pos);
        TextView time = (TextView)layout.findViewById(R.id.time);
        TextView player = (TextView)layout.findViewById(R.id.player);
        TextView createdAt = (TextView)layout.findViewById(R.id.created_at);

        ScoreItem item = (ScoreItem)getItem(pos);
        player.setText(item.player);
        position.setText(String.valueOf(new Integer(item.position)) + ".");
        time.setText(String.format("%.4f", item.time));
        createdAt.setText(item.created_at);

        return layout;
    }

    /**
     * Get the number of different views
     * 
     * @return int
     */
    public int getViewTypeCount() {

        return 1;
    }

    /**
     * Return wheather the items have stable IDs or not
     * 
     * @return boolean
     */
    public boolean hasStableIds() {

        return false;
    }

    /**
     * Return wheather the list is empty or not
     * 
     * @return boolean
     */
    public boolean isEmpty() {

        return this.scores.size() == 0;
    }

    /**
     * No need of a data observer
     * 
     * @param DataSetObserver arg0
     * @return void
     */
    public void registerDataSetObserver(DataSetObserver arg0) {

    }

    /**
     * No need of a data observer
     * 
     * @param DataSetObserver arg0
     * @return void
     */
    public void unregisterDataSetObserver(DataSetObserver arg0) {

    }

    /**
     * No item should be selectable
     * 
     * @return boolean
     */
    public boolean areAllItemsEnabled() {

        return false;
    }

    /**
     * No item should be selectable
     * 
     * @param int pos
     * @return boolean
     */
    public boolean isEnabled(int arg0) {

        return false;
    }
}

The Activity

The XMLLoaderThread works fine, it's just notifyDatasetChanged seems to do nothing...

/**
 * Obtain and display the online scores
 * 
 * @author soh#zolex
 *
 */
public class OnlineScoresDetails extends ListActivity {

    WakeLock wakeLock;
    OnlineScoresAdapter adapter;
    boolean isLoading = false;
    int chunkLimit = 50;
    int chunkOffset = 0;

    @Override
    /**
     * Load the scores and initialize the pager and adapter
     * 
     * @param Bundle savedInstanceState
     */
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        PowerManager powerManager = (PowerManager) getSystemService(Context.POWER_SERVICE);
        this.wakeLock = powerManager.newWakeLock(PowerManager.FULL_WAKE_LOCK, "racesow");

        adapter = new OnlineScoresAdapter(this);
        setListAdapter(adapter);
        this.loadData();

        setContentView(R.layout.listview);
        getListView().setOnScrollListener(new OnScrollListener() {

            public void onScrollStateChanged(AbsListView view, int scrollState) {

            }

            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {

                if (totalItemCount > 0 && visibleItemCount > 0 && firstVisibleItem + visibleItemCount >= totalItemCount) {

                    if (!isLoading) {

                        loadData();
                    }
                }
            }
        });
    }

    public void loadData() {

        final ProgressDialog pd = new ProgressDialog(OnlineScoresDetails.this);
        pd.setProgressStyle(ProgressDialog.STYLE_SPINNER);
        pd.setMessage("Obtaining scores...");
        pd.setCancelable(false);
        pd.show();

        isLoading = true;
        String mapName = getIntent().getStringExtra("map");
        XMLLoaderThread t = new XMLLoaderThread("http://racesow2d.warsow-race.net/map_positions.php?name=" + mapName + "&offset=" + this.chunkOffset + "&limit=" + this.chunkLimit, new Handler() {

            @Override
            public void handleMessage(Message msg) {

                switch (msg.what) {

                    // network error
                    case 0:
                        new AlertDialog.Builder(OnlineScoresDetails.this)
                            .setMessage("Could not obtain the maplist.\nCheck your network connection and try again.")
                            .setNeutralButton("OK", new OnClickListener() {

                                public void onClick(DialogInterface arg0, int arg1) {

                                    finish();
                                    overridePendingTransition(0, 0);
                                }
                            })
                            .show();
                        break;

                    // maplist received
                    case 1:
                        pd.dismiss();
                        InputStream xmlStream;
                        try {

                            xmlStream = new ByteArrayInputStream(msg.getData().getString("xml").getBytes("UTF-8"));
                            XMLParser parser = new XMLParser();
                            parser.read(xmlStream);

                            NodeList positions = parser.doc.getElementsByTagName("position");
                            int numPositions = positions.getLength();
                            for (int i = 0; i < numPositions; i++) {

                                Element position = (Element)positions.item(i);

                                ScoreItem score = new ScoreItem();
                                score.position = Integer.parseInt(parser.getValue(position, "no"));
                                score.player = parser.getValue(position, "player");
                                score.time = Float.parseFloat(parser.getValue(position, "time"));
                                score.created_at = parser.getValue(position, "created_at");

                                adapter.addItem(score);
                            }

                            adapter.notifyDataSetChanged();


                            chunkOffset += chunkLimit;
                            isLoading = false;

                        } catch (UnsupportedEncodingException e) {

                            new AlertDialog.Builder(OnlineScoresDetails.this)
                                .setMessage("Internal error: " + e.getMessage())
                                .setNeutralButton("OK", null)
                                .show();
                        }

                        break;
                }

                pd.dismiss();
            }
        });

        t.start();
    }

    /**
     * Acquire the wakelock on resume
     */
    public void onResume() {

        super.onResume();
        this.wakeLock.acquire();
    }

    /**
     * Release the wakelock when leaving the activity
     */
    public void onDestroy() {

        super.onDestroy();
        this.wakeLock.release();
    }

    /**
     * Disable animations when leaving the activity
     */
    public void onBackPressed() {

        this.finish();
        this.overridePendingTransition(0, 0);
    }
}

Answer 1

A bit late but the answer is you should not implement

public void registerDataSetObserver(DataSetObserver arg0) {

}

public void unregisterDataSetObserver(DataSetObserver arg0) {

}

I just had a simple BaseAdapter working as intended, who stop working after adding those two methods. I asume that "someone" need to observe data changes and such :)

Answer 2

I am not really sure if your implementation of Custom BaseAdapter is correct.

Try changing

public long getItemId(int pos) {
    return 0;
}

to

 public long getItemId(int pos) {
    return pos;
 }

I also found this simple tutorial that might be helpful on how to implement BaseAdapter. After you got this down, you can try notifyDataSetChanged() again.