Is there a way to prevent the listview from scrolling to its top position when its adapter's data is changed?

Question

I\'m having a bit of trouble preserving the scroll position of a list view when changing it\'s adapter\'s data.

What I\'m currently doing is to create a custom Array

Answer 1

In your Expandable/List Adapter, put this method

public void refresh(List<MyDataClass> dataList) {
    mDataList.clear();
    mDataList.addAll(events);
    notifyDataSetChanged();
}

And from your activity, where you want to update the list, put this code

if (mDataListView.getAdapter() == null) {
    MyDataAdapter myDataAdapter = new MyDataAdapter(mContext, dataList);
    mDataListView.setAdapter(myDataAdapter);
} else {
    ((MyDataAdapter)mDataListView.getAdapter()).refresh(dataList);
}

In case of Expandable List View, you will use mDataListView.getExpandableListAdapter() instead of mDataListView.getAdapter()

Answer 2

Check out: Maintain/Save/Restore scroll position when returning to a ListView

Use this to save the position in the ListView before you call .clear(), .addAll(), and . notifyDataSetChanged().

int index = mList.getFirstVisiblePosition();
View v = mList.getChildAt(0);
int top = (v == null) ? 0 : v.getTop();

After updating the ListView adapter, the Listview's items will be changed and then set the new position:

mList.setSelectionFromTop(index, top);

Basically you can save you position and scroll back to it, save the ListView state or the entire application state.

Other helpful links:

Save Position: How to save and restore ListView position in Android

Save State: Android ListView y position

Regards,

Please let me know if this helps!

Answer 3

As you pointed out yourself, the call to 'clear()' causes the position to be reset to the top.

Fiddling with scroll-position, etc. is a bit of a hack to get this working.

If your CustomListAdapter subclasses from ArrayAdapter, this could be the issue:

The call to clear(), calls 'notifyDataSetChanged()'. You can prevent this:

mListAdapter.setNotifyOnChange(false); // Prevents 'clear()' from clearing/resetting the listview
mListAdapter.clear();
mListAdapter.addAll(data.items);
// note that a call to notifyDataSetChanged() implicitly sets the setNotifyOnChange back to 'true'!
// That's why the call 'setNotifyOnChange(false) should be called first every time (see call before 'clear()').
mListAdapter.notifyDataSetChanged(); 

I haven't tried this myself, but try it :)

Answer 4

There is one more use-case I came across recently (Android 8.1) - caused by bug in Android code. If I use mouse-wheel to scroll list view - consecutive adapter.notifyDataSetChanged() resets scroll position to zero. Use this workaround until bug gets fixed in Android

        listView.onTouchModeChanged(true); // workaround
        adapter.notifyDataSetChanged();

More details is here: https://issuetracker.google.com/u/1/issues/130103876