listview not refreshing how to clear the listview items?

Question

I am using a custom Adapter class. And retrieving data from database using cursor. When user click a button it will open a custom dialog with single selection list and when user will choose a item from it a list will pop up. every time user will select a item the list must be refreshed.

My problem is that list items are appending to the previous list instead of refreshing.

Code-->

  public class ChannelListActivity extends Activity  {
  private Cursor countryCursor;
  private Cursor channelCursor;
  public  DbH db;
  private ArrayList <HashMap<String, Object>> channelAndRating;
  private HashMap<String, Object> hm;
  private static final String CHANNEL_NAME_KEY = "channel_names";
  private static final String RATINGKEY = "ratings";



    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);  
        ImageButton tv_button = (ImageButton)findViewById(R.id.tv_menu);
        final ListView listView = (ListView)findViewById(R.id.list);
        channelAndRating = new ArrayList<HashMap<String,Object>>();
        final myBaseAdapter baseadapter = new myBaseAdapter(channelAndRating, ChannelListActivity.this);


        try {
            db=new DbH(this);
        } catch (IOException e2) {

            e2.printStackTrace();
        }
        try {
             db.createdatabase();
        } catch (IOException e) {

             e.printStackTrace();
        }

        db.opendatabase();            
        countryCursor= db.dataCountryName();
         countryCursor.moveToFirst();
         final String country_names[] = new String[countryCursor.getCount()];

         final String country_id [] = new String [countryCursor.getCount()];

         for(int icount = 0 ; icount < countryCursor.getCount(); icount++) {
             country_names[icount] = countryCursor.getString(countryCursor.getColumnIndex("country"));
             country_id[icount] = countryCursor.getString(countryCursor.getColumnIndex("_id"));
             countryCursor.moveToNext();
         }




         tv_button.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                AlertDialog.Builder alt_bld = new AlertDialog.Builder(ChannelListActivity.this);
                alt_bld.setIcon(R.drawable.favourate_icon);
                alt_bld.setTitle("Select the Country ...");
                alt_bld.setSingleChoiceItems(country_names, -1, new DialogInterface.OnClickListener() {


                    public void onClick(DialogInterface dialog, int item) {
                     listView.setAdapter(null);
                    baseadapter.notifyDataSetChanged();
                     listView.setAdapter(baseadapter);
                     listView.setTextFilterEnabled(true);
                     Log.v("LIST VIEW ", "adapter is null fdf");
                     channelCursor = db.dataChannelsName(country_id[item]);
                     channelCursor.moveToFirst();
                     final String channels_name[] = new String[channelCursor.getCount()];
                     final int channel_rating[] =  new int [channelCursor.getCount()]; ;
                     for(int icount =0 ; icount<channelCursor.getCount(); icount++) {
                        channels_name[icount] = channelCursor.getString(channelCursor.getColumnIndex("name"));
                        channel_rating[icount] = Integer.parseInt(channelCursor.getString(channelCursor.getColumnIndex("votes")));
                        channelCursor.moveToNext(); 
                     }


                     for(int icount = 0 ;icount <channelCursor.getCount(); icount++)
                     {
                         hm = new HashMap<String, Object>();
                         hm.put(CHANNEL_NAME_KEY,channels_name[icount]);
                         hm.put(RATINGKEY, channel_rating[icount]);
                         channelAndRating.add(hm);
                     }

                Toast.makeText(getApplicationContext(), "Phone Model = "+country_id[item] +" " +country_names[item], Toast.LENGTH_SHORT).show();
                dialog.dismiss();

                  baseadapter.notifyDataSetChanged();
                  baseadapter.notifyDataSetInvalidated();



                }

                });
                AlertDialog alert = alt_bld.create();
                alert.show();

            }
        });
    }

        class myBaseAdapter extends BaseAdapter{
      private ArrayList<HashMap<String,Object>> cAndr;
      private LayoutInflater mInflater;




    public myBaseAdapter(ArrayList<HashMap<String, Object>> channelAndRating,
            Context channelListActivity) {

        cAndr = channelAndRating;
        mInflater = LayoutInflater.from(channelListActivity);


    }

    public int getCount() {

        return cAndr.size();
    }

    public Object getItem(int position) {

        return cAndr.get(position);
    }

    public long getItemId(int position) {

        return position;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;

        if(convertView==null) {
            convertView = mInflater.inflate(R.layout.list_box, null);
            holder = new ViewHolder();
            holder.tv = (TextView)convertView.findViewById(R.id.text1);
            holder.mRatingBar = (RatingBar)convertView.findViewById(R.id.star);
            convertView.setTag(holder);

           }    else {          
                         holder = (ViewHolder) convertView.getTag();
               }

         holder.tv.setText((String)cAndr.get(position).get(CHANNEL_NAME_KEY));
         holder.mRatingBar.setRating((Integer)cAndr.get(position).get(RATINGKEY));

         return convertView;
                }

class ViewHolder {
    RatingBar mRatingBar;
    TextView tv;
}


}

}

Any help would be highly appreciated!

Answer 1

You forgot to clear the list before filling it up again.

When a refresh is required, do a channelAndRating.clear(); first.

You can update the myBaseAdapter class and add a clear method to it:

class myBaseAdapter extends BaseAdapter{
      private ArrayList<HashMap<String,Object>> cAndr;
      private LayoutInflater mInflater;
      //.... Other stuff here
      public void clear(){
          cAndr.clear();
      }
}

Side note: in Java, class names always have the first letter in capital. I would rename myBaseAdapter and call it MyBaseAdapter instead