TableView API, no lazy retrieval of visible cell content possible?

Robert Krüger krueger at
Wed Jan 28 14:13:20 UTC 2015


On Wed, Jan 28, 2015 at 1:59 PM, Werner Lehmann <
lehmann at> wrote:

> Robert,
> I think Tomas is right, load your thumbnails on demand when updateItem is
> called for an item with missing thumbnail. You say that the cell of a
> visible item gets reused for another item. If that is the case I guess that
> the item is "moved" to another cell. Wouldn't it be possible to have an
> image property on your items and the lazy loading is done on the item,
> triggered when the item is passed to updateItem of any cell? That

That is exactly what I have implemented but the problem is as described
- Too many non-visible images are loaded (I could probably live with that
for a while)
- I have yet to find a criterion to decide an image is no longer needed and
thus its loading job needs to be removed from the job stack (see below)

> should trigger the demand-loading and it would be robust against the
> tableview exchanging cells for individual items.
As to the question when to start or stop lazy loading for items, I would
> add the load-demands to a stack. Each time the image for a new item is
> requested it is put to the top of the stack and you have one or more
> threads processing items on the stack (LIFO). An an image is requested
> which is already on the stack move it to the top of the stack. If an item
> is removed from a cell remove it from the stack. That should do it.
That's what I am doing already.



> On 28.01.2015 09:30, Robert Krüger wrote:
>> Doesn't help. The patterns of this property being changed are just as
>> unusable for my purposes as with the other approaches (e.g. I can clearly
>> see that item is set to a different value for a cell that is still
>> visible,
> ...

Robert Krüger
Managing Partner
Lesspain GmbH & Co. KG

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