notifyDataSetChanged() Notifies the attached observers that the underlying data has been changed and any View reflecting the data set should refresh itself.
It tells the ListView that the data has been modified; and to show the new data, the ListView must be redrawn.
If you are accessing it from outside scope, you can get it from the ListView object and cast it so you can call notifyDataSetChanged(). Like so: ServerItemAdapter listAdapter = (ServerItemAdapter) listView. getAdapter(); listAdapter.
Array Adapter is subclass of BaseAdapter. It is used to bind data in arrayList to AdapterView.
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:
ArrayAdapter
to modify the underlying List (add()
, insert()
, remove()
, clear()
, etc.)ArrayAdapter
with the new List
data. (Uses a lot of resources and garbage collection.)BaseAdapter
and ListAdapter
that allows changing of the underlying List
data structure.notifyDataSetChanged()
every time the list is updated. To call it on the UI-Thread, use the runOnUiThread()
of Activity
.
Then, notifyDataSetChanged()
will work.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();
}
});
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().
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<Object>(yourArrayList));
adapter.notifyDataSetChanged();
AdapterHelper class
public class AdapterHelper {
@SuppressWarnings({ "rawtypes", "unchecked" })
public void update(ArrayAdapter arrayAdapter, ArrayList<Object> listOfObject){
arrayAdapter.clear();
for (Object object : listOfObject){
arrayAdapter.add(object);
}
}
}
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!
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