Infinite Scroll View Revisited
Hi,
This has been bugging me for a while and today, I've managed to grab some time
in order to try and get it working.
I based my class on the Street Scroller Sample App from Apple. The main
methods that are important in Street Scroller are:
- (void)recenterIfNecessary
{
CGPoint currentOffset = [self contentOffset];
CGFloat contentWidth = [self contentSize].width;
CGFloat centerOffsetX = (contentWidth - [self bounds].size.width) / 2.0;
CGFloat distanceFromCenter = fabs(currentOffset.x - centerOffsetX);
if (distanceFromCenter (contentWidth / 4.0))
{
self.contentOffset = CGPointMake(centerOffsetX, currentOffset.y);
// move content by the same amount so it appears to stay still
for (UILabel *label in self.visibleLabels) {
CGPoint center = [self.labelContainerView convertPoint:label.center
toView:self];
center.x += (centerOffsetX - currentOffset.x);
label.center = [self convertPoint:center
toView:self.labelContainerView];
}
}
}
- (void)tileLabelsFromMinX:(CGFloat)minimumVisibleX
toMaxX:(CGFloat)maximumVisibleX
{
// the upcoming tiling logic depends on there already being at least one
label in the visibleLabels array, so
// to kick off the tiling we need to make sure there's at least one label
if ([self.visibleLabels count] == 0)
{
[self placeNewLabelOnRight:minimumVisibleX];
}
// add labels that are missing on right side
UILabel *lastLabel = [self.visibleLabels lastObject];
CGFloat rightEdge = CGRectGetMaxX([lastLabel frame]);
while (rightEdge maximumVisibleX)
{
rightEdge = [self placeNewLabelOnRight:rightEdge];
}
// add labels that are missing on left side
UILabel *firstLabel = self.visibleLabels[0];
CGFloat leftEdge = CGRectGetMinX([firstLabel frame]);
while (leftEdge minimumVisibleX)
{
leftEdge = [self placeNewLabelOnLeft:leftEdge];
}
// remove labels that have fallen off right edge
lastLabel = [self.visibleLabels lastObject];
while ([lastLabel frame].origin.x maximumVisibleX)
{
[lastLabel removeFromSuperview];
[self.visibleLabels removeLastObject];
lastLabel = [self.visibleLabels lastObject];
}
// remove labels that have fallen off left edge
firstLabel = self.visibleLabels[0];
while (CGRectGetMaxX([firstLabel frame]) minimumVisibleX)
{
[firstLabel removeFromSuperview];
[self.visibleLabels removeObjectAtIndex:0];
firstLabel = self.visibleLabels[0];
}
}
- (void)layoutSubviews
{
[super layoutSubviews];
[self recenterIfNecessary];
// tile content in visible bounds
CGRect visibleBounds = [self convertRect:[self bounds]
toView:self.labelContainerView];
CGFloat minimumVisibleX = CGRectGetMinX(visibleBounds);
CGFloat maximumVisibleX = CGRectGetMaxX(visibleBounds);
[self tileLabelsFromMinX:minimumVisibleX toMaxX:maximumVisibleX];
}
I'm got to the stage where as far as I can see recenterIfNecessary just
doesn't work correctly and I'm having difficulty trying to figure out what is
actually supposed to do?
I am trying to scroll infinitely through the following images (these are Test
Images so I can tell what is going on!), in the real app, these images will be
downloaded. The height is fixed at 200 but the Width is Variable.
Index File Name ImageSize XMin/XMax
0 Image01.png 200,200 ,0199
1 Image02.png 200,200 0200,0399
2 Image03.png 410,200 0400,0809
3 Image04.png 410,200 0810,1219
4 Image05.png 200,200 1220,1419
5 Image06.png 410,200 1420,1829
6 Image07.png 200,200 1830,2029
7 Image08.png 200,200 2030,2229
8 Image09.png 200,200 2230,2429
0/9 Image01.png 200,200 2430,2629
Wrap Around back to 0.
Total Width of all Images: 2430
In my Class, if I comment out the recenterIfNecessary call, all my Views get
added correctly and are shown in the correct order, and I can scroll them to
the end and it stops as expected.
With recenterIfNecessary enabled, as soon you begin the scroll and it runs
Frame Recalculation Loop, the Views go all over the place. So, I'm pretty sure
that this method is wrong (or at least my implementation of it is wrong, when
you take the rest of the code with it).
This the a dump of the Frame Rect for each view before and after the center has
been set.
Before myFramgeRect: {{0, 0}, {200, 200}}
After myFramgeRect: {{703, 0}, {200, 200}}
Before myFramgeRect: {{200, 0}, {200, 200}}
Re: Infinite Scroll View?
Hi,
Got it working! The problem was partly due to tiredness and partly due to a
misunderstanding about when layoutSubviews gets called.
If you look at the Street Scroller sample, you'll see that it has its content
in-built, in fact it generate new content on the fly. The problem I had was
that the content (images in this case) needed to be loaded externally from a
URL or from a file. Once I figured out how to get the process going it was ok
and I did it without having to add code to the delegate which is always a good
thing.
Thanks a lot to everyone that helped.
All the Best
Dave
On 9 Oct 2013, at 00:07, Damian Carrillo damiancarri...@me.com wrote:
Hi Dave,
What about if you have some repetition of the images? Say the following is a
container UIView that has all of your UIImageViews stacked horizontally and
the width of the following view is far smaller than that of the UIScrollView
it's contained in. The gray areas are duplicated image views, and the the
white area is the true set of images.
scroll.png
Say that in the previous image, the leftmost person is the first logical
image in your set of data. In your viewDidLoad, you could set the
contentOffset to the position of the first Person (ie. the leftmost white
edge) with something like:
- (void)viewDidLoad
{
CGFloat someXPos = CGRectGetWidth([pictures frame]) +
CGRectGetWidth([reticle frame]);
[scrollView setContentOffset:someXPos];
}
Then, once the user breaches the threshold value that has duplicates (the
gray areas), you call the following:
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
[scrollView setContentOffset:someXPos animated:NO];
}
The intent is that the scroll view snaps the container UIView back to a
position that contains no duplicates. The view has duplicates to account for
the period of time between sampling of scroll events. Note that this
suggestion is assuming that the images are fairly small, so that loading them
all doesn't cause too much memory pressure (which is what I understood from
earlier messages).
Damian
On Oct 8, 2013, at 4:53 PM, Dave d...@looktowindward.com wrote:
Hi,
Yes, I took a look, but it's not what I want to do. I have a number of
variable width images, not fixed width and all the examples I've seen use
pagingEnabled and have a fixed width.
Also the Street Scroller sample, just creates a label view on demand, which,
again isn't what I want. I have (say) 20 variable width images, so I want it
to scroll from image 1 to 20 and then back to 1. The samples doesn't do
anything like this.
Thanks anyway,
All the Best
Dave
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Re: Infinite Scroll View?
On 7 Oct 2013, at 19:54, Kyle Sluder k...@ksluder.com wrote:
On Mon, Oct 7, 2013, at 09:21 AM, Dave wrote:
Hi,
I'd like to be able to Scroll Infinitely in a Scroll, e.g. when the
scrolling is past the last item in the Scroll start displaying the first
and when scrolling before the first item, starting displaying the last.
The items in this case are UIImageViews and they have a fixed height and
a variable width and no one image will be wider that the Scroll View
itself. Also it needs to work with pagingEnables = NO, e.g. there will be
more than one Image visible.
I've playing around a bit and found a some sample code that sort of does
it but it doesn't handle the wrapping the Images smoothly (is was written
to have paging enabled).
My plan was/is to detect when the scrolling had hit before the
first/after the last and to move the first Subview to the End or the Last
one to the beginning, depending on the direction of movement, but at the
moment, I can't seem to see a way of detecting these conditions.
It seems fairly straightforward, if a little labor intensive, to figure
out the width and placement of all your image views, override
-layoutSubviews to position only the ones that are potentially visible,
and implement
-scrollViewWillEndDragging:withVelocity:targetContentOffset: to figure
out where to end scrolling, based on the current velocity.
--Kyle Sluder
Thanks Kyle,
That's what I was trying to figure out, whether I needed to re-layout the views
based on the positions or whether I could just do it by keeping an Array of the
image views separately and rotating this as it scroll past the end. I sort of
got this working, but of course the Subviews of the Scroll View just grows and
grows!
This is what I got at the moment:
// Scroll past last item detected (in the scrollViewDidScroll delegate method)
if (theScrollView.contentSize.width - theScrollView.contentOffset.x =
1024)
{
myContentInfo = [self.pContentArray objectAtIndex:0];
[self.pContentArray addObject:myContentInfo];
[self.pContentArray removeObjectAtIndex:0];
[self addContentInfo:myContentInfo withEndFlag:YES];
}
Which kind of works, but obviously isn't the way to do it.
Thanks for confirming I needed to use -layoutSubviews, I'm about to start on
this track now.
All the Best
Dave
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Re: Infinite Scroll View?
On Oct 8, 2013, at 12:44 AM, Dave d...@looktowindward.com wrote:
Thanks Kyle,
That's what I was trying to figure out, whether I needed to re-layout the
views based on the positions or whether I could just do it by keeping an
Array of the image views separately and rotating this as it scroll past the
end. I sort of got this working, but of course the Subviews of the Scroll
View just grows and grows!
This is what I got at the moment:
// Scroll past last item detected (in the scrollViewDidScroll delegate
method)
if (theScrollView.contentSize.width - theScrollView.contentOffset.x =
1024)
{
myContentInfo = [self.pContentArray objectAtIndex:0];
[self.pContentArray addObject:myContentInfo];
[self.pContentArray removeObjectAtIndex:0];
[self addContentInfo:myContentInfo withEndFlag:YES];
}
Which kind of works, but obviously isn't the way to do it.
Thanks for confirming I needed to use -layoutSubviews, I'm about to start on
this track now.
You don’t *have* to use -layoutSubviews, but you'll probably get the best
results if you do. You could theoretically do this all in the delegate's
implementation of -scrollViewDidScroll:, but that’ll probably double the number
of layout passes and certainly multiply the number of message sends. When
scrolling, you want to avoid as much unnecessary work as is reasonable.
It’s kind of a bummer that you’re going to need to split your logic up between
the scroll view and its delegate, thus tightly coupling the two. I wish the
frameworks exposed many more of their delegate hooks as subclass hooks as well.
Scroll views seem to stir this desire particularly frequently.
--Kyle Sluder
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Re: Infinite Scroll View?
Hi,
I finally managed to get back on this! I've got it working when scrolling from
left to right and can detect when the user scrolls past the last item, however,
I can't seem to find a way to detect when the user scrolls to before the first
item.
I get -0 for offset X
2013-10-08 20:18:20.607 LTWScrollTest1[17988:a0b] contentOffset: {-0, 0}
But that doesn't do me much good!
It seems to work quite nicely going left to right, but having difficulties
figuring out how to make it work scrolling right to left.
Any idea greatly appreciated as I'm need to get this working for tomorrow
morning!
Thanks a lot.
All the Best
Dave
On 8 Oct 2013, at 08:56, Kyle Sluder k...@ksluder.com wrote:
On Oct 8, 2013, at 12:44 AM, Dave d...@looktowindward.com wrote:
Thanks Kyle,
That's what I was trying to figure out, whether I needed to re-layout the
views based on the positions or whether I could just do it by keeping an
Array of the image views separately and rotating this as it scroll past the
end. I sort of got this working, but of course the Subviews of the Scroll
View just grows and grows!
This is what I got at the moment:
// Scroll past last item detected (in the scrollViewDidScroll delegate
method)
if (theScrollView.contentSize.width - theScrollView.contentOffset.x =
1024)
{
myContentInfo = [self.pContentArray objectAtIndex:0];
[self.pContentArray addObject:myContentInfo];
[self.pContentArray removeObjectAtIndex:0];
[self addContentInfo:myContentInfo withEndFlag:YES];
}
Which kind of works, but obviously isn't the way to do it.
Thanks for confirming I needed to use -layoutSubviews, I'm about to start on
this track now.
You don’t *have* to use -layoutSubviews, but you'll probably get the best
results if you do. You could theoretically do this all in the delegate's
implementation of -scrollViewDidScroll:, but that’ll probably double the
number of layout passes and certainly multiply the number of message sends.
When scrolling, you want to avoid as much unnecessary work as is reasonable.
It’s kind of a bummer that you’re going to need to split your logic up
between the scroll view and its delegate, thus tightly coupling the two. I
wish the frameworks exposed many more of their delegate hooks as subclass
hooks as well. Scroll views seem to stir this desire particularly frequently.
--Kyle Sluder
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Re: Infinite Scroll View?
Does (scrollView.contentOffset.x = 0) not work? How are you testing for it now?
On Oct 8, 2013, at 12:20 PM, Dave d...@looktowindward.com wrote:
Hi,
I finally managed to get back on this! I've got it working when scrolling
from left to right and can detect when the user scrolls past the last item,
however, I can't seem to find a way to detect when the user scrolls to before
the first item.
I get -0 for offset X
2013-10-08 20:18:20.607 LTWScrollTest1[17988:a0b] contentOffset: {-0, 0}
But that doesn't do me much good!
It seems to work quite nicely going left to right, but having difficulties
figuring out how to make it work scrolling right to left.
Any idea greatly appreciated as I'm need to get this working for tomorrow
morning!
Thanks a lot.
All the Best
Dave
On 8 Oct 2013, at 08:56, Kyle Sluder k...@ksluder.com wrote:
On Oct 8, 2013, at 12:44 AM, Dave d...@looktowindward.com wrote:
Thanks Kyle,
That's what I was trying to figure out, whether I needed to re-layout the
views based on the positions or whether I could just do it by keeping an
Array of the image views separately and rotating this as it scroll past the
end. I sort of got this working, but of course the Subviews of the Scroll
View just grows and grows!
This is what I got at the moment:
// Scroll past last item detected (in the scrollViewDidScroll delegate
method)
if (theScrollView.contentSize.width - theScrollView.contentOffset.x =
1024)
{
myContentInfo = [self.pContentArray objectAtIndex:0];
[self.pContentArray addObject:myContentInfo];
[self.pContentArray removeObjectAtIndex:0];
[self addContentInfo:myContentInfo withEndFlag:YES];
}
Which kind of works, but obviously isn't the way to do it.
Thanks for confirming I needed to use -layoutSubviews, I'm about to start
on this track now.
You don’t *have* to use -layoutSubviews, but you'll probably get the best
results if you do. You could theoretically do this all in the delegate's
implementation of -scrollViewDidScroll:, but that’ll probably double the
number of layout passes and certainly multiply the number of message sends.
When scrolling, you want to avoid as much unnecessary work as is reasonable.
It’s kind of a bummer that you’re going to need to split your logic up
between the scroll view and its delegate, thus tightly coupling the two. I
wish the frameworks exposed many more of their delegate hooks as subclass
hooks as well. Scroll views seem to stir this desire particularly frequently.
--Kyle Sluder
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Re: Infinite Scroll View?
Well, it never goes less than -0 whatever that means so the is redundant
and 0 is a valid offset, I need to detect a scroll to *before* 0, which I never
get.
Thanks
Dave
On 8 Oct 2013, at 21:26, Steve Christensen puns...@mac.com wrote:
Does (scrollView.contentOffset.x = 0) not work? How are you testing for it
now?
On Oct 8, 2013, at 12:20 PM, Dave d...@looktowindward.com wrote:
Hi,
I finally managed to get back on this! I've got it working when scrolling
from left to right and can detect when the user scrolls past the last item,
however, I can't seem to find a way to detect when the user scrolls to
before the first item.
I get -0 for offset X
2013-10-08 20:18:20.607 LTWScrollTest1[17988:a0b] contentOffset: {-0, 0}
But that doesn't do me much good!
It seems to work quite nicely going left to right, but having difficulties
figuring out how to make it work scrolling right to left.
Any idea greatly appreciated as I'm need to get this working for tomorrow
morning!
Thanks a lot.
All the Best
Dave
On 8 Oct 2013, at 08:56, Kyle Sluder k...@ksluder.com wrote:
On Oct 8, 2013, at 12:44 AM, Dave d...@looktowindward.com wrote:
Thanks Kyle,
That's what I was trying to figure out, whether I needed to re-layout the
views based on the positions or whether I could just do it by keeping an
Array of the image views separately and rotating this as it scroll past
the end. I sort of got this working, but of course the Subviews of the
Scroll View just grows and grows!
This is what I got at the moment:
// Scroll past last item detected (in the scrollViewDidScroll delegate
method)
if (theScrollView.contentSize.width - theScrollView.contentOffset.x =
1024)
{
myContentInfo = [self.pContentArray objectAtIndex:0];
[self.pContentArray addObject:myContentInfo];
[self.pContentArray removeObjectAtIndex:0];
[self addContentInfo:myContentInfo withEndFlag:YES];
}
Which kind of works, but obviously isn't the way to do it.
Thanks for confirming I needed to use -layoutSubviews, I'm about to start
on this track now.
You don’t *have* to use -layoutSubviews, but you'll probably get the best
results if you do. You could theoretically do this all in the delegate's
implementation of -scrollViewDidScroll:, but that’ll probably double the
number of layout passes and certainly multiply the number of message sends.
When scrolling, you want to avoid as much unnecessary work as is reasonable.
It’s kind of a bummer that you’re going to need to split your logic up
between the scroll view and its delegate, thus tightly coupling the two. I
wish the frameworks exposed many more of their delegate hooks as subclass
hooks as well. Scroll views seem to stir this desire particularly
frequently.
--Kyle Sluder
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Re: Infinite Scroll View?
Hi,
Spoke too soon!
I just can't seem to get my head around this. I can make it work, but I'm
getting into an infinite loop because updating the scroll view is causing the
delegates to fire again (AFAICT). I'm not sure what to put in layoutSubviews
and what to put in the delegate methods. I'm beginning to think this just isn't
possible with UIScrollView and wondering if I should burn a DTS Support Request
on it.
This would be so easy if I just had the source to UIScrollView!
All the Best
Dave
On 8 Oct 2013, at 20:20, Dave d...@looktowindward.com wrote:
Hi,
I finally managed to get back on this! I've got it working when scrolling
from left to right and can detect when the user scrolls past the last item,
however, I can't seem to find a way to detect when the user scrolls to before
the first item.
I get -0 for offset X
2013-10-08 20:18:20.607 LTWScrollTest1[17988:a0b] contentOffset: {-0, 0}
But that doesn't do me much good!
It seems to work quite nicely going left to right, but having difficulties
figuring out how to make it work scrolling right to left.
Any idea greatly appreciated as I'm need to get this working for tomorrow
morning!
Thanks a lot.
All the Best
Dave
On 8 Oct 2013, at 08:56, Kyle Sluder k...@ksluder.com wrote:
On Oct 8, 2013, at 12:44 AM, Dave d...@looktowindward.com wrote:
Thanks Kyle,
That's what I was trying to figure out, whether I needed to re-layout the
views based on the positions or whether I could just do it by keeping an
Array of the image views separately and rotating this as it scroll past the
end. I sort of got this working, but of course the Subviews of the Scroll
View just grows and grows!
This is what I got at the moment:
// Scroll past last item detected (in the scrollViewDidScroll delegate
method)
if (theScrollView.contentSize.width - theScrollView.contentOffset.x =
1024)
{
myContentInfo = [self.pContentArray objectAtIndex:0];
[self.pContentArray addObject:myContentInfo];
[self.pContentArray removeObjectAtIndex:0];
[self addContentInfo:myContentInfo withEndFlag:YES];
}
Which kind of works, but obviously isn't the way to do it.
Thanks for confirming I needed to use -layoutSubviews, I'm about to start
on this track now.
You don’t *have* to use -layoutSubviews, but you'll probably get the best
results if you do. You could theoretically do this all in the delegate's
implementation of -scrollViewDidScroll:, but that’ll probably double the
number of layout passes and certainly multiply the number of message sends.
When scrolling, you want to avoid as much unnecessary work as is reasonable.
It’s kind of a bummer that you’re going to need to split your logic up
between the scroll view and its delegate, thus tightly coupling the two. I
wish the frameworks exposed many more of their delegate hooks as subclass
hooks as well. Scroll views seem to stir this desire particularly frequently.
--Kyle Sluder
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Re: Infinite Scroll View?
Did you check the StreetScroller sample?
https://developer.apple.com/library/ios/samplecode/StreetScroller/Introduction/Intro.html#//apple_ref/doc/uid/DTS40011102
it is the same code that was demonstrated in the WWDC 2011 I told you before.
--
:: marcelo.alves
On 08/10/2013, at 17:30, Dave d...@looktowindward.com wrote:
Hi,
Spoke too soon!
I just can't seem to get my head around this. I can make it work, but I'm
getting into an infinite loop because updating the scroll view is causing the
delegates to fire again (AFAICT). I'm not sure what to put in layoutSubviews
and what to put in the delegate methods. I'm beginning to think this just
isn't possible with UIScrollView and wondering if I should burn a DTS Support
Request on it.
This would be so easy if I just had the source to UIScrollView!
All the Best
Dave
On 8 Oct 2013, at 20:20, Dave d...@looktowindward.com wrote:
Hi,
I finally managed to get back on this! I've got it working when scrolling
from left to right and can detect when the user scrolls past the last item,
however, I can't seem to find a way to detect when the user scrolls to
before the first item.
I get -0 for offset X
2013-10-08 20:18:20.607 LTWScrollTest1[17988:a0b] contentOffset: {-0, 0}
But that doesn't do me much good!
It seems to work quite nicely going left to right, but having difficulties
figuring out how to make it work scrolling right to left.
Any idea greatly appreciated as I'm need to get this working for tomorrow
morning!
Thanks a lot.
All the Best
Dave
On 8 Oct 2013, at 08:56, Kyle Sluder k...@ksluder.com wrote:
On Oct 8, 2013, at 12:44 AM, Dave d...@looktowindward.com wrote:
Thanks Kyle,
That's what I was trying to figure out, whether I needed to re-layout the
views based on the positions or whether I could just do it by keeping an
Array of the image views separately and rotating this as it scroll past
the end. I sort of got this working, but of course the Subviews of the
Scroll View just grows and grows!
This is what I got at the moment:
// Scroll past last item detected (in the scrollViewDidScroll delegate
method)
if (theScrollView.contentSize.width - theScrollView.contentOffset.x =
1024)
{
myContentInfo = [self.pContentArray objectAtIndex:0];
[self.pContentArray addObject:myContentInfo];
[self.pContentArray removeObjectAtIndex:0];
[self addContentInfo:myContentInfo withEndFlag:YES];
}
Which kind of works, but obviously isn't the way to do it.
Thanks for confirming I needed to use -layoutSubviews, I'm about to start
on this track now.
You don’t *have* to use -layoutSubviews, but you'll probably get the best
results if you do. You could theoretically do this all in the delegate's
implementation of -scrollViewDidScroll:, but that’ll probably double the
number of layout passes and certainly multiply the number of message sends.
When scrolling, you want to avoid as much unnecessary work as is reasonable.
It’s kind of a bummer that you’re going to need to split your logic up
between the scroll view and its delegate, thus tightly coupling the two. I
wish the frameworks exposed many more of their delegate hooks as subclass
hooks as well. Scroll views seem to stir this desire particularly
frequently.
--Kyle Sluder
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Re: Infinite Scroll View?
Hi,
Yes, I took a look, but it's not what I want to do. I have a number of variable
width images, not fixed width and all the examples I've seen use pagingEnabled
and have a fixed width.
Also the Street Scroller sample, just creates a label view on demand, which,
again isn't what I want. I have (say) 20 variable width images, so I want it to
scroll from image 1 to 20 and then back to 1. The samples doesn't do anything
like this.
Thanks anyway,
All the Best
Dave
On 8 Oct 2013, at 22:01, Marcelo Alves marcelo.al...@me.com wrote:
Did you check the StreetScroller sample?
https://developer.apple.com/library/ios/samplecode/StreetScroller/Introduction/Intro.html#//apple_ref/doc/uid/DTS40011102
it is the same code that was demonstrated in the WWDC 2011 I told you
before.
--
:: marcelo.alves
On 08/10/2013, at 17:30, Dave d...@looktowindward.com wrote:
Hi,
Spoke too soon!
I just can't seem to get my head around this. I can make it work, but I'm
getting into an infinite loop because updating the scroll view is causing
the delegates to fire again (AFAICT). I'm not sure what to put in
layoutSubviews and what to put in the delegate methods. I'm beginning to
think this just isn't possible with UIScrollView and wondering if I should
burn a DTS Support Request on it.
This would be so easy if I just had the source to UIScrollView!
All the Best
Dave
On 8 Oct 2013, at 20:20, Dave d...@looktowindward.com wrote:
Hi,
I finally managed to get back on this! I've got it working when scrolling
from left to right and can detect when the user scrolls past the last item,
however, I can't seem to find a way to detect when the user scrolls to
before the first item.
I get -0 for offset X
2013-10-08 20:18:20.607 LTWScrollTest1[17988:a0b] contentOffset: {-0, 0}
But that doesn't do me much good!
It seems to work quite nicely going left to right, but having difficulties
figuring out how to make it work scrolling right to left.
Any idea greatly appreciated as I'm need to get this working for tomorrow
morning!
Thanks a lot.
All the Best
Dave
On 8 Oct 2013, at 08:56, Kyle Sluder k...@ksluder.com wrote:
On Oct 8, 2013, at 12:44 AM, Dave d...@looktowindward.com wrote:
Thanks Kyle,
That's what I was trying to figure out, whether I needed to re-layout the
views based on the positions or whether I could just do it by keeping an
Array of the image views separately and rotating this as it scroll past
the end. I sort of got this working, but of course the Subviews of the
Scroll View just grows and grows!
This is what I got at the moment:
// Scroll past last item detected (in the scrollViewDidScroll delegate
method)
if (theScrollView.contentSize.width - theScrollView.contentOffset.x =
1024)
{
myContentInfo = [self.pContentArray objectAtIndex:0];
[self.pContentArray addObject:myContentInfo];
[self.pContentArray removeObjectAtIndex:0];
[self addContentInfo:myContentInfo withEndFlag:YES];
}
Which kind of works, but obviously isn't the way to do it.
Thanks for confirming I needed to use -layoutSubviews, I'm about to start
on this track now.
You don’t *have* to use -layoutSubviews, but you'll probably get the best
results if you do. You could theoretically do this all in the delegate's
implementation of -scrollViewDidScroll:, but that’ll probably double the
number of layout passes and certainly multiply the number of message
sends. When scrolling, you want to avoid as much unnecessary work as is
reasonable.
It’s kind of a bummer that you’re going to need to split your logic up
between the scroll view and its delegate, thus tightly coupling the two. I
wish the frameworks exposed many more of their delegate hooks as subclass
hooks as well. Scroll views seem to stir this desire particularly
frequently.
--Kyle Sluder
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Re: Infinite Scroll View?
Hi Dave,
What about if you have some repetition of the images? Say the following is a
container UIView that has all of your UIImageViews stacked horizontally and the
width of the following view is far smaller than that of the UIScrollView it's
contained in. The gray areas are duplicated image views, and the the white area
is the true set of images.
Say that in the previous image, the leftmost person is the first logical image
in your set of data. In your viewDidLoad, you could set the contentOffset to
the position of the first Person (ie. the leftmost white edge) with something
like:
- (void)viewDidLoad
{
CGFloat someXPos = CGRectGetWidth([pictures frame]) +
CGRectGetWidth([reticle frame]);
[scrollView setContentOffset:someXPos];
}
Then, once the user breaches the threshold value that has duplicates (the gray
areas), you call the following:
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
[scrollView setContentOffset:someXPos animated:NO];
}
The intent is that the scroll view snaps the container UIView back to a
position that contains no duplicates. The view has duplicates to account for
the period of time between sampling of scroll events. Note that this suggestion
is assuming that the images are fairly small, so that loading them all doesn't
cause too much memory pressure (which is what I understood from earlier
messages).
Damian
On Oct 8, 2013, at 4:53 PM, Dave d...@looktowindward.com wrote:
Hi,
Yes, I took a look, but it's not what I want to do. I have a number of
variable width images, not fixed width and all the examples I've seen use
pagingEnabled and have a fixed width.
Also the Street Scroller sample, just creates a label view on demand, which,
again isn't what I want. I have (say) 20 variable width images, so I want it
to scroll from image 1 to 20 and then back to 1. The samples doesn't do
anything like this.
Thanks anyway,
All the Best
Dave
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Infinite Scroll View?
Hi,
I'd like to be able to Scroll Infinitely in a Scroll, e.g. when the scrolling
is past the last item in the Scroll start displaying the first and when
scrolling before the first item, starting displaying the last. The items in
this case are UIImageViews and they have a fixed height and a variable width
and no one image will be wider that the Scroll View itself. Also it needs to
work with pagingEnables = NO, e.g. there will be more than one Image visible.
I've playing around a bit and found a some sample code that sort of does it but
it doesn't handle the wrapping the Images smoothly (is was written to have
paging enabled).
My plan was/is to detect when the scrolling had hit before the first/after the
last and to move the first Subview to the End or the Last one to the beginning,
depending on the direction of movement, but at the moment, I can't seem to see
a way of detecting these conditions.
I logged contentOffset and contentSize in the scrollViewDidScroll delegate
method and got these results:
scrollViewDidScroll Offset: {4017, 0} - Size: {5119, 200}
scrollViewDidScroll Offset: {4061, 0} - Size: {5119, 200}
scrollViewDidScroll Offset: {4095, 0} - Size: {5119, 200}
When hitting the end and
scrollViewDidScroll Top Scroll View Offset: {106, 0} - Size: {5119, 200}
scrollViewDidScroll Top Scroll View Offset: {24, 0} - Size: {5119, 200}
scrollViewDidScroll Top Scroll View Offset: {-0, 0} - Size: {5119, 200}
When hitting the start.
I'm not sure how if I can detect the start/end conditions using these values?
Any points on the best way to implement this would greatly appreciated!
All the Best
Dave
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Re: Infinite Scroll View?
There’s a WWDC video from 2011 : “Advanced ScrollView Techniques” which
explains one way to do infinite scrolling. Look at 18:08 if it is what you want.
On 07/10/2013, at 13:21, Dave d...@looktowindward.com wrote:
Hi,
I'd like to be able to Scroll Infinitely in a Scroll, e.g. when the scrolling
is past the last item in the Scroll start displaying the first and when
scrolling before the first item, starting displaying the last. The items in
this case are UIImageViews and they have a fixed height and a variable width
and no one image will be wider that the Scroll View itself. Also it needs to
work with pagingEnables = NO, e.g. there will be more than one Image visible.
I've playing around a bit and found a some sample code that sort of does it
but it doesn't handle the wrapping the Images smoothly (is was written to
have paging enabled).
My plan was/is to detect when the scrolling had hit before the first/after
the last and to move the first Subview to the End or the Last one to the
beginning, depending on the direction of movement, but at the moment, I can't
seem to see a way of detecting these conditions.
I logged contentOffset and contentSize in the scrollViewDidScroll delegate
method and got these results:
scrollViewDidScroll Offset: {4017, 0} - Size: {5119, 200}
scrollViewDidScroll Offset: {4061, 0} - Size: {5119, 200}
scrollViewDidScroll Offset: {4095, 0} - Size: {5119, 200}
When hitting the end and
scrollViewDidScroll Top Scroll View Offset: {106, 0} - Size: {5119, 200}
scrollViewDidScroll Top Scroll View Offset: {24, 0} - Size: {5119, 200}
scrollViewDidScroll Top Scroll View Offset: {-0, 0} - Size: {5119, 200}
When hitting the start.
I'm not sure how if I can detect the start/end conditions using these values?
Any points on the best way to implement this would greatly appreciated!
All the Best
Dave
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Re: Infinite Scroll View?
Have you thought about representing your images as cells in a UITableView? If
so, you could use something like BBTableView
(https://github.com/bharath2020/UITableViewTricks). It's a subclass of
UITableView lays out cells along an arc but it also has support for infinite
scrolling, so you could just use the relevant pieces. Plus UITableView will
handle putting the right image in the right vertical location, based on your
data source.
On Oct 7, 2013, at 9:21 AM, Dave d...@looktowindward.com wrote:
Hi,
I'd like to be able to Scroll Infinitely in a Scroll, e.g. when the scrolling
is past the last item in the Scroll start displaying the first and when
scrolling before the first item, starting displaying the last. The items in
this case are UIImageViews and they have a fixed height and a variable width
and no one image will be wider that the Scroll View itself. Also it needs to
work with pagingEnables = NO, e.g. there will be more than one Image visible.
I've playing around a bit and found a some sample code that sort of does it
but it doesn't handle the wrapping the Images smoothly (is was written to
have paging enabled).
My plan was/is to detect when the scrolling had hit before the first/after
the last and to move the first Subview to the End or the Last one to the
beginning, depending on the direction of movement, but at the moment, I can't
seem to see a way of detecting these conditions.
I logged contentOffset and contentSize in the scrollViewDidScroll delegate
method and got these results:
scrollViewDidScroll Offset: {4017, 0} - Size: {5119, 200}
scrollViewDidScroll Offset: {4061, 0} - Size: {5119, 200}
scrollViewDidScroll Offset: {4095, 0} - Size: {5119, 200}
When hitting the end and
scrollViewDidScroll Top Scroll View Offset: {106, 0} - Size: {5119, 200}
scrollViewDidScroll Top Scroll View Offset: {24, 0} - Size: {5119, 200}
scrollViewDidScroll Top Scroll View Offset: {-0, 0} - Size: {5119, 200}
When hitting the start.
I'm not sure how if I can detect the start/end conditions using these values?
Any points on the best way to implement this would greatly appreciated!
All the Best
Dave
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Re: Infinite Scroll View?
Hi,
I don't think that will work for me in this case as I need the images to be
scrolled smoothly without gaps and AFAIK, using a table view cell will cause a
gap - you can add a fragment of an image.
Thanks anyway
All the Best
Dave
On 7 Oct 2013, at 18:11, Steve Christensen puns...@mac.com wrote:
Have you thought about representing your images as cells in a UITableView? If
so, you could use something like BBTableView
(https://github.com/bharath2020/UITableViewTricks). It's a subclass of
UITableView lays out cells along an arc but it also has support for infinite
scrolling, so you could just use the relevant pieces. Plus UITableView will
handle putting the right image in the right vertical location, based on your
data source.
On Oct 7, 2013, at 9:21 AM, Dave d...@looktowindward.com wrote:
Hi,
I'd like to be able to Scroll Infinitely in a Scroll, e.g. when the
scrolling is past the last item in the Scroll start displaying the first and
when scrolling before the first item, starting displaying the last. The
items in this case are UIImageViews and they have a fixed height and a
variable width and no one image will be wider that the Scroll View itself.
Also it needs to work with pagingEnables = NO, e.g. there will be more than
one Image visible.
I've playing around a bit and found a some sample code that sort of does it
but it doesn't handle the wrapping the Images smoothly (is was written to
have paging enabled).
My plan was/is to detect when the scrolling had hit before the first/after
the last and to move the first Subview to the End or the Last one to the
beginning, depending on the direction of movement, but at the moment, I
can't seem to see a way of detecting these conditions.
I logged contentOffset and contentSize in the scrollViewDidScroll delegate
method and got these results:
scrollViewDidScroll Offset: {4017, 0} - Size: {5119, 200}
scrollViewDidScroll Offset: {4061, 0} - Size: {5119, 200}
scrollViewDidScroll Offset: {4095, 0} - Size: {5119, 200}
When hitting the end and
scrollViewDidScroll Top Scroll View Offset: {106, 0} - Size: {5119, 200}
scrollViewDidScroll Top Scroll View Offset: {24, 0} - Size: {5119, 200}
scrollViewDidScroll Top Scroll View Offset: {-0, 0} - Size: {5119, 200}
When hitting the start.
I'm not sure how if I can detect the start/end conditions using these values?
Any points on the best way to implement this would greatly appreciated!
All the Best
Dave
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Re: Infinite Scroll View?
Does it not work to set the row height to the height of each of the images and
then use a custom UITableViewCell that contains a UIImageView that fills the
cell? The other benefit is that you don't have to have more images in memory
than are visible within the table view's frame. (This may not be an issue if
there aren't that many, of course.)
On Oct 7, 2013, at 10:25 AM, Dave d...@looktowindward.com wrote:
Hi,
I don't think that will work for me in this case as I need the images to be
scrolled smoothly without gaps and AFAIK, using a table view cell will cause
a gap - you can add a fragment of an image.
Thanks anyway
All the Best
Dave
On 7 Oct 2013, at 18:11, Steve Christensen puns...@mac.com wrote:
Have you thought about representing your images as cells in a UITableView?
If so, you could use something like BBTableView
(https://github.com/bharath2020/UITableViewTricks). It's a subclass of
UITableView lays out cells along an arc but it also has support for infinite
scrolling, so you could just use the relevant pieces. Plus UITableView will
handle putting the right image in the right vertical location, based on your
data source.
On Oct 7, 2013, at 9:21 AM, Dave d...@looktowindward.com wrote:
Hi,
I'd like to be able to Scroll Infinitely in a Scroll, e.g. when the
scrolling is past the last item in the Scroll start displaying the first
and when scrolling before the first item, starting displaying the last. The
items in this case are UIImageViews and they have a fixed height and a
variable width and no one image will be wider that the Scroll View itself.
Also it needs to work with pagingEnables = NO, e.g. there will be more than
one Image visible.
I've playing around a bit and found a some sample code that sort of does it
but it doesn't handle the wrapping the Images smoothly (is was written to
have paging enabled).
My plan was/is to detect when the scrolling had hit before the first/after
the last and to move the first Subview to the End or the Last one to the
beginning, depending on the direction of movement, but at the moment, I
can't seem to see a way of detecting these conditions.
I logged contentOffset and contentSize in the scrollViewDidScroll delegate
method and got these results:
scrollViewDidScroll Offset: {4017, 0} - Size: {5119, 200}
scrollViewDidScroll Offset: {4061, 0} - Size: {5119, 200}
scrollViewDidScroll Offset: {4095, 0} - Size: {5119, 200}
When hitting the end and
scrollViewDidScroll Top Scroll View Offset: {106, 0} - Size: {5119, 200}
scrollViewDidScroll Top Scroll View Offset: {24, 0} - Size: {5119, 200}
scrollViewDidScroll Top Scroll View Offset: {-0, 0} - Size: {5119, 200}
When hitting the start.
I'm not sure how if I can detect the start/end conditions using these
values?
Any points on the best way to implement this would greatly appreciated!
All the Best
Dave
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Re: Infinite Scroll View?
On Mon, Oct 7, 2013, at 11:04 AM, Steve Christensen wrote: Does it not work to set the row height to the height of each of the images and then use a custom UITableViewCell that contains a UIImageView that fills the cell? The other benefit is that you don't have to have more images in memory than are visible within the table view's frame. (This may not be an issue if there aren't that many, of course.) Dave is scrolling horizontally, not vertically. UITableView is of no help here. --Kyle Sluder ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Infinite Scroll View?
On Mon, Oct 7, 2013, at 09:21 AM, Dave wrote: Hi, I'd like to be able to Scroll Infinitely in a Scroll, e.g. when the scrolling is past the last item in the Scroll start displaying the first and when scrolling before the first item, starting displaying the last. The items in this case are UIImageViews and they have a fixed height and a variable width and no one image will be wider that the Scroll View itself. Also it needs to work with pagingEnables = NO, e.g. there will be more than one Image visible. I've playing around a bit and found a some sample code that sort of does it but it doesn't handle the wrapping the Images smoothly (is was written to have paging enabled). My plan was/is to detect when the scrolling had hit before the first/after the last and to move the first Subview to the End or the Last one to the beginning, depending on the direction of movement, but at the moment, I can't seem to see a way of detecting these conditions. It seems fairly straightforward, if a little labor intensive, to figure out the width and placement of all your image views, override -layoutSubviews to position only the ones that are potentially visible, and implement -scrollViewWillEndDragging:withVelocity:targetContentOffset: to figure out where to end scrolling, based on the current velocity. --Kyle Sluder ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
