Android ListView not refreshing after notifyDataSetChanged

Question

My ListFragment code   public class ItemFragment extends ListFragment        private DatabaseHandler dbHelper      private static final String TITLE    Items       private static final String LOG TAG    debugger       private ItemAdapter adapter      private List lt Item gt  items         Override     public View onCreateView LayoutInflater inflater  ViewGroup container  Bundle savedInstanceState            View view   inflater inflate R layout item fragment list  container  false                   return view              Override     public void onCreate Bundle savedInstanceState            super setHasOptionsMenu true           super onCreate savedInstanceState           getActivity   setTitle TITLE           dbHelper   new DatabaseHandler getActivity             items   dbHelper getItems             adapter   new ItemAdapter getActivity   getApplicationContext    items           this setListAdapter adapter                  Override     public void onResume             super onResume            items clear            items   dbHelper getItems      reload the items from database         adapter notifyDataSetChanged                Override     public void onListItemClick ListView l  View v  int position  long id            super onListItemClick l  v  position  id           if dbHelper    null      item is edited             Item item    Item  this getListAdapter   getItem position               Intent intent   new Intent getActivity    AddItemActivity class               intent putExtra IntentConstants ITEM  item               startActivity intent                       My ListView   lt  xml version  1 0  encoding  utf-8   gt   lt LinearLayout xmlns android  http   schemas android com apk res android      android layout width  fill parent      android layout height  fill parent      android orientation  vertical   gt        lt ListView         android id   android id list          android layout width  fill parent          android layout height  wrap content    gt    lt  LinearLayout gt    But this does not refresh the ListView  Even after restarting app the updated items are not shown  My ItemAdapter extends BaseAdapter  public class ItemAdapter extends BaseAdapter       private LayoutInflater inflater      private List lt Item gt  items      private Context context       public ProjectListItemAdapter Context context  List lt Item gt  items            super            inflater   LayoutInflater from context           this context   context          this items   items               Override     public int getCount             return items size                Override     public Object getItem int position            return items get position               Override     public long getItemId int position            return position              Override     public View getView int position  View convertView  ViewGroup parent            ItemViewHolder holder   null          if convertView    null                holder   new ItemViewHolder                convertView   inflater inflate R layout list item  parent false               holder itemName    TextView  convertView findViewById R id topText               holder itemLocation    TextView  convertView findViewById R id bottomText               convertView setTag holder             else               holder    ItemViewHolder  convertView getTag                      holder itemName setText  Name      items get position  getName             holder itemLocation setText  Location      items get position  getLocation             if position   2    0                                                                                                 convertView setBackgroundColor context getResources   getColor R color evenRowColor              else                   convertView setBackgroundColor context getResources   getColor R color oddRowColor                      return convertView             private static class ItemViewHolder           TextView itemName          TextView itemLocation            Can someone help please

User · Accepted Answer

Look at your onResume method in ItemFragment    Override public void onResume         super onResume        items clear        items   dbHelper getItems       reload the items from database     adapter notifyDataSetChanged        what you just have updated before calling notifyDataSetChanged   is not the adapter s field private List lt Item gt  items  but the identically declared field of the fragment  The adapter still stores a reference to list of items you passed when you created the adapter  e g  in fragment s onCreate   The shortest  in sense of number of changes  but not elegant way to make your code behave as you expect is simply to replace the line       items   dbHelper getItems       reload the items from database   with       items addAll dbHelper getItems        reload the items from database   A more elegant solution   1  remove items private List lt Item gt  items  from ItemFragment - we need to keep reference to them only in adapter  2  change onCreate to     Override public void onCreate Bundle savedInstanceState        super onCreate savedInstanceState       super setHasOptionsMenu true       getActivity   setTitle TITLE       dbHelper   new DatabaseHandler getActivity         adapter   new ItemAdapter getActivity    dbHelper getItems         setListAdapter adapter       3  add method in ItemAdapter   public void swapItems List lt Item gt  items        this items   items      notifyDataSetChanged        4  change your onResume to    Override public void onResume         super onResume        adapter swapItems dbHelper getItems

User · Answer

You are assigning reloaded items to global variable items in onResume    but this will not reflect in ItemAdapter class  because it has its own instance variable called  items    For refreshing ListView  add a refresh   in ItemAdapter class which accepts list data i e items  class ItemAdapter                  public void refresh List lt Item gt  items                this items   items          notifyDataSetChanged               update onResume   with following code   Override public void onResume         super onResume        items clear        items   dbHelper getItems      reload the items from database       adapter refresh items

User · Answer

adapter setNotifyDataChanged     should do the trick

User · Answer

If your list is contained in the Adapter itself  calling the function that updates the list should also call notifyDataSetChanged     Running this function from the UI Thread did the trick for me   The refresh   function inside the Adapter  public void refresh          manipulate list     notifyDataSetChanged        Then in turn run this function from the UI Thread  getActivity   runOnUiThread new Runnable           Override     public void run               adapter refresh

User · Answer

If you want to update your listview doesn t matter if you want to do that on onResume    onCreate   or in some other function  first thing that you have to realize is that you won t need to create a new instance of the adapter  just populate the arrays with your data again  The idea is something similar to this     private ArrayList lt String gt  titles  private MyListAdapter adapter  private ListView myListView    Override public void onCreate Bundle savedInstanceState       super onCreate savedInstanceState       setContentView R layout main activity        myListView    ListView  findViewById R id my list        titles   new ArrayList lt String gt         for int i  0  i lt 20 i             titles add  Title   i              adapter   new MyListAdapter this  titles       myListView setAdapter adapter        Override public void onResume        super onResume           first clear the items and populate the new items     titles clear        for int i  0  i lt 20 i             titles add  New Title   i             adapter notifySetDataChanged        So depending on that answer you should use the same List lt Item gt  in your Fragment  In your first adapter initialization you fill your list with the items and set adapter to your listview  After that in every change in your items you have to clear the values from the main List lt Item gt  items and than populate it again with your new items and call notifySetDataChanged      That s how it works

User · Answer

adpter notifyDataSetInvalidated      Try this in onPause   method of Activity class

User · Answer

An answer from AlexGo did the trick for me   getActivity   runOnUiThread new Runnable              Override         public void run              messages add m            adapter notifyDataSetChanged             getListView   setSelection messages size  -1                   List Update worked for me before when the update was triggered from a GUI event  thus being in the UI thread   However  when I update the list from another event thread - i e  a call from outside the app  the update would not be in the UI thread and it ignored the call to getListView  Calling the update with runOnUiThread as above did the trick for me  Thanks

User · Answer

In onResume   change this line  items   dbHelper getItems      reload the items from database   to  items addAll dbHelper getItems       reload the items from database   The problem is that you re never telling your adapter about the new items list  If you don t want to pass a new list to your adapter  as it seems you don t   then just use items addAll after your clear    This will ensure you are modifying the same list that the adapter has a reference to

User · Answer

Try this    Override public void onResume     super onResume    items clear    items   dbHelper getItems      reload the items from database adapter   new ItemAdapter getActivity    items    reload the items from database adapter notifyDataSetChanged

User · Answer

Try like this    this notifyDataSetChanged      instead of    adapter notifyDataSetChanged      You have to notifyDataSetChanged   to the ListView not to the adapter class

User · Answer

If the adapter is already set  setting it again will not refresh the listview  Instead first check if the listview has a adapter and then call the appropriate method   I think its not a very good idea to create a new instance of the adapter while setting the list view  Instead  create an object   BuildingAdapter adapter   new BuildingAdapter context        if getListView   getAdapter      null     Adapter not set yet       setListAdapter adapter             else    Already has an adapter     adapter notifyDataSetChanged            Also you might try to run the refresh list on UI Thread   activity runOnUiThread new Runnable                      public void run                     do your modifications here                   for example                   adapter add new Object                   adapter notifyDataSetChanged

[android] Android ListView not refreshing after notifyDataSetChanged

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