I would like to create an infinite scrollView (like a slot machine), but without paging. When the user scrolls down, it's easy i just have to increase the contentSize and the scrollView scroll endlessly :
- (void)scrollViewDidScroll:(UIScrollView *)theScrollView {
theScrollView.contentSize = CGSizeMake(45, theScrollView.contentSize.height+45);
}
But how can i create the same effect when the user scrolls upward ? I tried to play with the contentInset but then the contentOfsset doesn't get updated and i end up having weird behaviour.
Do you have any idea how i could achieve that ?
I needed the same, so I created this: http://dev.doukasd.com/2011/04/infinite-scrolling-dial-control-for-ios/
Have a look at the video, I believe it's what you're looking for. Source code is included.
I have developed this kind scroll view. It can scroll infinite.
You can check on github: https://github.com/quangrubify/InfiniteUITableView
I think you should give us more details about the issue. What content do you want the user to see when he is scrolling upwards? You increase the contentSize in scrollViewDidScroll method, but you are not checking the contentOffset, so the contentWill be bigger whenever the user scrolls the scrollView (either way, even horizontal if allowed). Since the contentOffset is already at 0, the user cant scroll upwards because there is nothing that the scroll view can show.
I dont know the content of your scrollView, but I have implemented infinite scrolling horizontally. For details, see: https://stackoverflow.com/a/12856174/936957
PS: Do not use "magic numbers", this is a better alternative:
theScrollView.contentSize = CGSizeMake(theScrollView.contentSize.x, theScrollView.contentSize.height+45);
//Or theScrollView.frame.size.width alternatively
Related
I have a UIScroll view with content in it. If that content overflows, making the scroll view scrollable, I'd like to set the bottom of the view to be a certain color. If it does not, I'd like to set it to a different color.
My issue is, I do not know how to detect if a UIScrollView's content overflows and thus is scrollable.
Check if the scroll view's contentSize is bigger than its bounds.
I know it's an old question, but my scroll view had a content insets set which made the accepted answer slightly off. Here's how to take the content inset into account:
if scrollView.contentSize.height + scrollView.contentInset.bottom > scrollView.bounds.size.height {
// Scroll view is able to scroll.
}
I have a ContentView with a StackLayout with multiple children sized to the full width of the screen. In other words, if the screen width is 320 and I have five children, the inner StackLayout is resized to 1600.
In this ContentView, I have Next and Previous buttons that when clicked, animate the inner StackLayout's TranslateX property. Basically, I'm creating a carousel by translating the StackLayout within the ContentView. I chose this route because I was having layout issues using a ScrollView and a custom renderer when I would modify that layout of the view (by hiding labels, etc.)
However, I've hit a snag. Content that appears after I set the TranslateX property doesn't receive any tap events. I believe I might have to reset some tappable area, but I'm not even sure where to begin with that. Does anyone have any suggestions?
I posted this same question in Xamarin's Forums, and someone there answered. For anyone looking, the answer is here: https://forums.xamarin.com/discussion/comment/142914/#Comment_142914
If that link stops working at some point in the future for some reason, the relevant answer is:
Hit testing is done based on the actual frame of the control determined by layout, but translation happens after layout. Therefore hit testing does not take translation into account. If you want a view to be touchable then you should update its layout directly rather than using translation.
I'm trying to learn auto layout so I can set up a moderately complicated display the way I want. I'm starting with a simple version. At least I thought it was simple.
I have a content view containing a NSScrollView, and a zoom slider. The scroll view is, of course, just a window into a larger 'canvas' on which the user can do things.
I'd like the scroll view to be as big as the window allows, with the slider underneath.
I've tried many things none of which work, in some cases when I resize the window smaller, the scroll view goes on up over the window's top bar, obscuring the title and the red yellow, green, dots.. this is just a grumble, I won't attempt to describe how I got it.
I'm working with Visual Format Language.
The immediate problem: I can only get the thing to work at all if I put in a hard size constraint on the scroll view.
I've got constraints like #"V:|[ScrollView]-[ZoomSlider(==35)]-| and
#"|-20#1000-[ScrollView]-|"
With these, nothing shows at all, until I put a hard size on the scroll view:
For example, #"V:[ScrollView(>=70#20)]" and #"[ScrollView(>=140#20)]" results in a little tiny scroll view (as expected) just above the slider.
Window is resizable, all right.
Is there a simple way to make the scroll view resize to occupy the most space possible when I resize the window? The only way I can think of off hand is to produce metrics for the scroll view based on window size, and use a notification to change the constraints when the window size changes. There should be something simpler!
THanks.ee
OOps. Thought I knew the answer until I started to write it.
AT least here is a partial explanation of things that were causing me problems.
You can't add constraints that position or size the Window's content view. But apparently you can mess them up by deleting them programatically. Some of my problems were solved by getting rid of
[self.myContentView setTranslatesAutoresizingMaskIntoConstraints:NO];
and
[self.myContentView removeConstraints:self.myContentView.constraints];
This left me with a lot of conflicting constraints. I fixed this be eliminating all content window constraints that I could in IB, then by marking the rest as placeholders.
I've got a ways to go before I understand how to use auto layout, but doing it in code is easier (for me) than doing it with IB
You see this in iPhone apps like Gilt. The user scrolls a view, and a subview apparently "sticks" to one edges as the rest of the scrollView slides underneath. That is, there is a text box (or whatever) in the scrollView, that as the scrollView hits the top of the view, then "sticks" there as the rest of the view continues to slide.
So, there are several issues. First, one can determine via "scrollViewDidScroll:" (during normal scrolling) when the view of interest is passing (or re-appearing). There is a fair amount of granularity here - the differences between delegate calls can be a hundred of points or more. That said, when you see the view approach the top of the scrollView, you turn on a second copy of the view statically displayed under the scrollView top. I have not coded this, but it seems like it will lack a real "stick" look - the view will first disappear then reappear.
Second, if one does a setContentOffset:animated, one does not get the delegate messages (Gilt does not do this). So, how do you get the callbacks in this case? Do you use KVO on "scroll.layer.presentationLayer.bounds" ?
Well, I found one way to do this. When the user scrolls by flicking and dragging, the UIScrollView gives its delegate a "scrollViewDidScroll:" message. You can look then to see if the scroller has moved the content to where you need to take some action.
When "sticking" the view, remove it from the scrollView, and then add it to the scrollView's superview (with an origin of 0,0). When unsticking, do the converse.
If you use the UIScrollView setContentOffset:animated:, it gets trickier. What I did was to subclass UIScrollView, use a flag to specify it was setContentOffset moving the offset, then start a fast running timer to monitor contentOffset.
I put the method that handles the math and sticking/unsticking the child view into this subclass. It looks pretty good.
Gilt uses a table view to accomplish this. Specifically, in the table view's delegate, these two methods:
– tableView:viewForHeaderInSection:
and – tableView:heightForHeaderInSection:
I have been trying to create a simple swipe transition. However buttons seem immune to any CAAnimation that crops.
I am trying to get it so that a bar moves across the screen and as it goes over the button it removes the part it has just gone over.
I have tried bounds.width, size.x and many other key-value paths to achieve the affect but I haven't got what I wanted. It just relocates the text which always remains entirely visible
I have also tried changing the UIButton to a UIImage but the text does not seem to print on a UIImage.
I tried using masks too but I have heard they should be used as infrequently as possible as they consume the phones resources. I didn't really get very far with this either anyway as I hadn't used them much before.
I also tried placing it in a container view and then change the dimensions of that but again all of the text remained entirely visible.
I know I could have a view hide the button but I am trying to reveal the view behind as the bar swipes.
Does anyone have any suggestions of how to achieve a swipe transition on a UIButton?
Help would be much appreciated.
Thanks
I think what you're looking for really is a mask. See the tutorial here:
http://iosdevelopertips.com/cocoa/how-to-mask-an-image.html
What I'd do in your situation is create a custom UIButton class, and add a mask as in the tutorial, then animate the position of the mask. Slide the mask of, nothing shows. Slide it on, part shows until the whole thing is visible.
Edit: I haven't really heard anything about hogging resources, especially since it appears to be simple core graphics.