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Android ListView scrolling to top

Posted by: admin November 30, 2017 Leave a comment

Questions:

I have a ListView with custom rows. When any of these rows is
clicked, the ListView’s data is regenerated. I’d like the list to
scroll back to the top when this happens.

I initially tried using setSelection(0) in each row’s OnClickListener
to achieve this but was unsuccessful (I believe because the ListView
loses its scroll position when its data is invalidated – so my call to
setSelection is undone. I still don’t understand how the ListView
decides where to scroll to after invalidation, though).

The only working solution I know of was given by Romain Guy here:
http://groups.google.com/group/android-developers/browse_thread/thread/127ca57414035301

It involves (View.post)ing the call to _listView.setSelection(0). I
found this to perform quite poorly.
The newly generated list shows up with its scroll location unchanged
and there is a considerable delay before it scrolls back to the top.

Is there any better way to achieve this functionality?

Any help would be much appreciated.

Thanks!

Answers:

call listView.setSelectionAfterHeaderView(); to scroll to top

Questions:
Answers:

I have tried lot but this one worked for me

list.smoothScrollToPosition(0);

Questions:
Answers:

I simply use listview.setSelection(0);

Works fine for me.

Questions:
Answers:

Personally, I recommend you find a different UI pattern. It is possible that users will find your current “click, and the list changes in situ” approach intuitive, but I am skeptical.

You could try subclassing ListView and overriding layoutChildren() to chain to the superclass, then call setSelection(0) in the case where that is needed. If the “considerable delay” is due to just the post() call, this should clear it up.

Questions:
Answers:

If you need instant scroll just after ListView adapter’s data was changed, pay attention that it might not be yet populated. In this case you should post() your setSelection() or setSelectionAfterHeaderView() via Handler so it will be called later in the queue.

listView.Handler.post(new Runnable() {
            @Override
            public void run() {
                listView.setSelectionAfterHeaderView();    
            }
        });

This worked for me.

Questions:
Answers:

as a workaround, you can create a new adapter containing the new regenerated data, then call ListView.setAdapter. after that call ListView.setSelection(n).

btw, the solution provided by commonsware is worked.

Questions:
Answers:

On some different requirement.
If you want to scroll up just like while chatting.

        mListView.smoothScrollToPosition(mAdapter.getCount());