[android-developers] Re: Flaky Touch Screen on Nexus One

On Apr 30, 11:05 pm, Streets Of Boston <flyingdutc...@gmail.com>
wrote:
> Yes, you're right about that. Calling notifyDataSetChanged on the adapter is
> the best way to go and you should use it in 99% of cases. However, in some
> cases rules should be broken. :)
> A call to notifyDataSetChanged redraws all the children in the ListView and
> is relatively expensive and you get the side effects you notice in your
> example (touch issues).
> In this case, another solution may be necessary, where visible list-items
> (child-views of the ListView) or their children update *themselves*.
> You could do this by tagging list-item views (contentView-s) by calling
> setTag an do a getTag on all the ListView's child-views to be able to find
> them back when they need updating.

I continue to disagree with this. First of all, the ListView should
only be redrawing what is visible on the screen. That is why the
Adaptor has a getView(int position...) method, so that the ListView
can be smart about which views it needs to redraw. Second of all, the
children VIEWS should not be responsible for updating themselves when
the underlying data changes. This is precisely why the ListView's
Adaptor has a notifyDatasetChanged! So that you can give a hint do
the ListView that the data has changed, and so that it can ask for the
Views it needs to update. the getView() method on Adaptor also has a
"View convertView" arg so that it can pass the getView() method a
recycled view to update. At the very worst, Adaptor needs to be
updated to have a "notifyDatasetChangedAtIndex(int[] indexes)" method
so that the ListView can be even smarter about which row(s) to
redisplay (instead of redisplaying the visible rows as it currently
does). In any case, I just don't see why my VIEW code should be smart
about updating itself when the underlying data changes; in other words
isn't that what the Adaptor is supposed to do for me?

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