notifyDataSetChanged example

Question

I m trying to use in my Android Application the notifyDataSetChanged   method for an ArrayAdapter but it doesn t work for me    I found as answer here  that notifyDataSetChanged   should run in the main thread  but there was no example for that   Could anybody send an example or at least a link

User · Answer

I know this is a late response but I was facing a similar issue and I managed to solve it by using notifyDataSetChanged() in the right place.

So my situation was as follows.

I had to update a listview in an action bar tab (fragment) with contents returned from a completely different activity. Initially however, the listview would not reflect any changes. However, when I clicked another tab and then returned to the desired tab,the listview would be updated with the correct content from the other activity. So to solve this I used notifyDataSetChanged() of the action bar adapter in the code of the activity which had to return the data.

This is the code snippet which I used in the activity.

@Override
public boolean onOptionsItemSelected(MenuItem item) {

    switch (item.getItemId()) 
    {
        case R.id.action_new_forward:

            FragmentTab2.mListAdapter.notifyDataSetChanged();//this updates the adapter in my action bar tab
            Intent ina = new Intent(getApplicationContext(), MainActivity.class);
            ina.putExtra("stra", values1);
            startActivity(ina);// This is the code to start the parent activity of my action bar tab(fragment).
    }
}

This activity would return some data to FragmentTab2 and it would directly update my listview in FragmentTab2.

Hope someone finds this useful!

User · Answer

I had the same problem and I prefer not to replace the entire ArrayAdapter with a new instance continuously  Thus I have the AdapterHelper do the heavy lifting somewhere else   Add this where you would normally  try to  call notify  new AdapterHelper   update  ArrayAdapter adapter  new ArrayList lt Object gt  yourArrayList    adapter notifyDataSetChanged      AdapterHelper class   public class AdapterHelper        SuppressWarnings    rawtypes    unchecked         public void update ArrayAdapter arrayAdapter  ArrayList lt Object gt  listOfObject           arrayAdapter clear            for  Object object   listOfObject               arrayAdapter add object

User · Answer

For an ArrayAdapter  notifyDataSetChanged only works if you use the add    insert    remove    and clear   on the Adapter     When an ArrayAdapter is constructed  it holds the reference for the List that was passed in   If you were to pass in a List that was a member of an Activity  and change that Activity member later  the ArrayAdapter is still holding a reference to the original List   The Adapter does not know you changed the List in the Activity   Your choices are    Use the functions of the ArrayAdapter to modify the underlying List  add    insert    remove    clear    etc   Re-create the ArrayAdapter with the new List data   Uses a lot of resources and garbage collection   Create your own class derived from BaseAdapter and ListAdapter that allows changing of the underlying List data structure  Use the notifyDataSetChanged   every time the list is updated  To call it on the UI-Thread  use the runOnUiThread   of Activity  Then  notifyDataSetChanged   will work

User · Answer

You can use the runOnUiThread   method as follows   If you re not using a ListActivity  just adapt the code to get a reference to your ArrayAdapter   final ArrayAdapter adapter     ArrayAdapter getListAdapter     runOnUiThread new Runnable         public void run             adapter notifyDataSetChanged

User · Answer

I recently wrote on this topic  though this post it old  I thought it will be helpful to someone who wants to know how to implement BaseAdapter notifyDataSetChanged   step by step and in a correct way   Please follow How to correctly implement BaseAdapter notifyDataSetChanged   in Android or the newer blog BaseAdapter notifyDataSetChanged

[android] notifyDataSetChanged example

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