After I have gotten the data for a single row of a ListView
, I want to update that single row.
Currently I am using notifyDataSetChanged();
but that makes the View
react very slowly. Are there any other solutions?
As Romain Guy explained a while back during the Google I/O session, the most efficient way to only update one view in a list view is something like the following (this one update the whole view data):
ListView list = getListView();
int start = list.getFirstVisiblePosition();
for(int i=start, j=list.getLastVisiblePosition();i<=j;i++)
if(target==list.getItemAtPosition(i)){
View view = list.getChildAt(i-start);
list.getAdapter().getView(i, view, list);
break;
}
Assuming target
is one item of the adapter.
This code retrieve the ListView
, then browse the currently shown views, compare the target
item you are looking for with each displayed view items, and if your target is among those, get the enclosing view and execute the adapter getView
on that view to refresh the display.
As a side note invalidate
doesn't work like some people expect and will not refresh the view like getView does, notifyDataSetChanged
will rebuild the whole list and end up calling getview
for every displayed items and invalidateViews
will also affect a bunch.
One last thing, one can also get extra performance if he only needs to change a child of a row view and not the whole row like getView
does. In that case, the following code can replace list.getAdapter().getView(i, view, list);
(example to change a TextView
text):
((TextView)view.findViewById(R.id.myid)).setText("some new text");
In code we trust.