Thank you everyone I have this working (locally in memory anyway)... I
had to tweak the method a little bit...
- (UIImage*)imageNamed:(NSString*)imageNamed cache:(BOOL)cache
{
UIImage* retImage = [staticImageDictionary objectForKey:imageNamed];
if (retImage == nil)
{
// Since my
To fix the stutter, use a blank image for when the image doesn't exist
- do the NSData dataWithContentsOfURL in another thread so that when
it finishes it posts a notification which then the cell will listen to
and refresh with the data cached. Its a bit more involved and you have
to do
Be aware that you may run into memory issues if you cache too many
images in memory. You should be able to respond to this situation by
using UIViewController's didReceiveMemoryWarning method and releasing
some of those images.
Luke
On May 13, 2009, at 6:23 AM, Eric E. Dolecki wrote:
I have zero experience with threads, and while that does sound good, I don't
know how to do that yet.
Eric
On Wed, May 13, 2009 at 1:06 PM, Alex Kac a...@webis.net wrote:
To fix the stutter, use a blank image for when the image doesn't exist -
do the NSData dataWithContentsOfURL in another
Take heart, Eric. Threads aren't all that bad -- coding is simple,
hardest part is debugging (should your code executing in the new
thread is doing something unadvisable), but if you keep it simple, it
should be fairly straightforward.
Good luck,
Brad
On May 13, 2009, at 10:36 AM, Eric
I've just printed out the API docs on NSThread and need to start reading up
on it.
I assume that's the API I'd want to use. Now, does each image fetch need to
be it's own thread (I'm thinking yes). Is there a limit to how many can be
going at once? Is the iPhone multi-threaded? I have to figure
It would be possible to implement one thread that would handle all
image download requests, or you could just spin a new thread for each
image download. The latter is simpler to code, so I'd lean toward
that. There's a limit somewhere on the number of threads in one
process, but it's
So is it safe to approach threads like they were timers? You start a thread,
and it calls back to it's selector method when it's complete
(detachNewThreadSelector:toTarget:withObject)?
Now - what if a thread completes and the cell is currently out of view (it
was scrolled) - do the internals take
On May 13, 2009, at 11:45 AM, Eric E. Dolecki wrote:
So is it safe to approach threads like they were timers? You start a
thread, and it calls back to it's selector method when it's complete
(detachNewThreadSelector:toTarget:withObject)?
I would conclude my thread with a line like:
It could cause an error. The way I handle it is this.
1) You have a UIImageView in the cell.
2) Assign it a tag that's unique. imageView.tag = some unique id
3) Since cells are re-used, you need reset the tag in prepareForReuse
and make sure to set it in the cellForIndexPath.
4) In the image
I haven't seen performSelectorOnMainThread before.
Should that call go into the selector method that's called? ie...
// This kicks off a thread
[NSThread detachNewThreadSelector:@selector(threadLoad:) toTarget:self
withObject:myArrayWithDictionary];
Now...
-(void)threadLoad:(id)param {
//
Yes, something like that. I should mention that it's probably best to
send in the NSIndexPath to the cell you're interested in rather than a
pointer to the cell itself. Then you can call [tableView
cellForRowAtIndexPath:indexPath] to get the cell just before your
performeSelectorOnMain
In my table, when a cell isn't nil I am setting UILabels, etc. However, in
each cell I have a UIImageView... and the contents of each is an image
fetched from my server. No problem on initial display, but as soon as you
start scrolling and the cells are reused, I am fetching new artwork... which
You should be able to easily implement your own caching mechanism for
your content. Keep the images around, either in memory or on disk, as
appropriate, and just refresh them when you need to.
Luke
On May 12, 2009, at 2:04 PM, Eric E. Dolecki wrote:
In my table, when a cell isn't nil I am
Yes, if you cache them yourself.
Dave
On Tuesday, May 12, 2009, at 03:04PM, Eric E. Dolecki edole...@gmail.com
wrote:
In my table, when a cell isn't nil I am setting UILabels, etc. However, in
each cell I have a UIImageView... and the contents of each is an image
fetched from my server. No
Okay, so I know I can somehow cache them... but I have some noob questions.
- how do I cache the images themselves? Some binary data object written to
the disk? How?
- how do I check if the image has already been loaded (check an
NSMutableArray populated with dictionaries with a url string and url
Obviously, if you want to cache the images between runs of the
application, you need to cache them as binary onto the disk. If you
are OK with the images being loaded after every launch of the
application, you can cache them into an NSMutableDictionary with the
URL as the key, and the
On May 12, 2009, at 2:13 PM, Eric E. Dolecki wrote:
Okay, so I know I can somehow cache them... but I have some noob
questions.
- how do I cache the images themselves? Some binary data object
written to
the disk? How?
If you're caching to memory, all you really need to do is retain the
Eric,
I think one of the more effective ways to cache images is to store
your image to the file system, and then store meta-data for that image
in a local SQL database. That meta-data should include a last
updated date for the image. Then, instead of requesting the image
directly from
I wish that Apple provided a convenient method for doing this as it seems
like something that could regularly be employed. I don't think I'll go as
far as using SQL, but thanks for all the tips!!
On Tue, May 12, 2009 at 7:11 PM, Bradley S. O'Hearne
br...@bighillsoftware.com wrote:
Eric,
I
On May 12, 2009, at 4:38 PM, Eric E. Dolecki wrote:
I wish that Apple provided a convenient method for doing this as it
seems like something that could regularly be employed. I don't think
I'll go as far as using SQL, but thanks for all the tips!!
It doesn't really make sense for Apple to
Eric,
For what it is worth -- Luke is right. There are probably so many
variations on how developers would want such a cache managed, and the
fact that it couldn't be self-contained inside a single API object (or
for that matter, tier, as it would require server cooperation too),
that it
I like the cache without writing to the disk (for now anyway).
When you say the image object itself, I don't know exactly what you mean...
if it's just a pointer to UIImage then I think I do know. So I could pair
the pointer with the URL key, is that right?
E.
On Tue, May 12, 2009 at 5:19 PM,
The UIImage is the object (inherits from NSObject), so yes you'd pass
the pointer to it as the dict's object. And objectForKey: will pass
back that pointer to the UIImage again.
On May 12, 2009, at 10:00 PM, Eric E. Dolecki wrote:
I like the cache without writing to the disk (for now
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