I've been working with a UIScrollView and have about 200 items to scroll through...so far. This doesn't work since it takes around 45 seconds to load all of the views. I've tried loading the first 20 (about 4 seconds) on the main thread then load in blocks of 50 on other threads. I get the first 20 to scroll through but the others don't appear.
It's taken lots of effort just to get the UIScrollView to work properly and there are still some issues. The UITableView will solve all of this for me since it reuses cells. It's similar to the UIScrollView except more efficient.
I'd like to have one cell take up the entire viewing area and have the user flick through each cell. Rather than freely scrolling through cells, scrolling will stop at each cell and the user must flick again for the next cell. The UITableView doesn't do this that I know of. Is there a way to get this behavior with a UITableView?
UITableView is a subclass of UIScrollView. Have you tried simply setting yourTableView.pagingEnabled = YES?
Short answer: no.
You can try to control UITableView's scrolling behavior using the delegate methods, or better yet, stick with UIScrollView and load the views one-by-one in the UIScrollViewDelegate methods.
Related
I have a few very long collectionViews, all nested inside a scrollView.
since the prefetching range is related to the scrollView, all the cells are "visible" on the scrollView, even though most of them are not visible on the screen at all.
Hence, when calling reloadData(), it reloads all the cells, instead of reloading only the visible cells. it ends up in a very long UI freeze.
Is there a way to load only the cells that are truly visible on the screen?
The "best" way to do this is to put everything inside a UITableView which has UICollectionViews as cells. It sounds horrible (and tbh, its not very nice) but it's really the only "clean" way to do this.
Let the UITableView act as the ScrollView and everything else should work just fine, it should, all in all, be much faster and shouldn't lock up the UI.
I just saw a brilliant application Nimbuzz. In its chat window, when there are couple of messages and we scroll the UITableView, what appears to be is, scrolling speed is slow. It may sound weird what I just said. You may also consider it this way. On scrolling the table, not much rows are scrolled in comparison to usual scroll behavior.
I am creating an application where I need the similar feature. How to do that?
I think you do that with scrollview's decelerationRate property. Since tableview is subview of scrollview it would work.
I need a "PickerView", that behaves like a normal UIPickerView, but only shows one row of data and has a custom design.
Something like you see in the image, showing the transition from subview 1 to subview 2. After the user lifts his finger and after the scrolling stops, only one subview will be shown:
IMAGE
So basically a scrollview which:
is endless in both, positive and negative directions by showing the same entries over and over
uses paging across several subviews
only shows one subview when not scrolling, and no more than two subviews when scrolling.
I can get a endless scrollview to work, but not with paging enabled. Paging will always limit my scrolling to the next subview.
So I'm thinking about creating my own UIView subclass which custom scrolling behaviour to mimic a UIPickerView. But before doing so, I wanted to get some opinions about the idea in general. Is creating a custom UIView the right way to go? Anyone has some experience with the expected performace? (There will be timers to handle the scrolling algorithm, which has to be recreated of course... :)
Another approach would be to subclass UIScrolView and implement the paging myself. I know when the scrollView starts decelerating
, so maybe there is a way to overwrite the contentOffset to have it scroll into the right position...?!
Any help is appreciated! Thanks!
Here is a great custom component, which seems to be able to do everything you need:
http://dev.doukasd.com/2011/04/infinite-scrolling-dial-control-for-ios/
It's not endless, but rather a modified UITableView with a huge number of cells.
Would it be feasible to just use a UIPickerView, but clipped to the middle row? You could turn off showsSelectionIndicator to remove the overlay and have the delegate pass back custom row views.
I want to scrolltableview horizontally as well as vertically. How can I do it?
I'd suggest making a UIScrollView the same size as the screen and then making your UITableView bigger than the screen.Drop the TableView into the ScrollView. Set up the scrollview with a high contenSize.width and then tweak it to work as you desire.
The idea with embedding UITableView into UIScrollView seems to be great, however there is a serious gotcha. UITableView is optimized to display only visible viewpoirt area and limiting allocated UITableView cells. In the case it is embedded into UIScrollView, it allocates complete content area of scroll view, i.e. all rows for the UITableView. It goes out of the memory for approximatelly 2000 rows. Since the UITableView.reloadData creates callback in main thread, it blocks main thread to respond to didReceiveMemoryWarning and application is killed on system sole discretion for level 2 warning, which is never received.
It seems that the better way is in subclassing UITableView and extending rows to width which can be scrolled horizontally.
If you are looking for something similar to what is done in 'Pulse', then this tutorial might help you:
http://iosstuff.wordpress.com/2011/06/29/creating-pulse-style-scrolling-horizontally-scrolling-uitableview-as-a-subview-of-uitableviewcell/
It shows how to add a horizontally scrolling UITableView to a vertically scrolling UITableView
I have a UIScrollView that I am using to simulate a UITableView like interaction because rows are a bit more complex than what UITableView has to offer. I have 4 UILables a UIImageView and a UIButton for every row. The end result is a lot of subviews.
Even with only 10 rows,the scroll view that looks fine in the simulator but has a fairly low frame rate on the iPhone 4. This is a resource consumption issue for sure.
Is there a way to optimize the redraw durring scrolling like double buffering?
If not is there another way to get customizable UITableview functionality?
thanks
Does every View have 4xUILabels, a UIImageView and a UIButton?
I would create a nib file with a custom UITableViewCell (You can make those as complex as you want), then you can reuse the cells to help with your performance.
Information on how to do this is here:
http://developer.apple.com/iphone/library/documentation/UserExperience/Conceptual/TableView_iPhone/TableViewCells/TableViewCells.html#//apple_ref/doc/uid/TP40007451-CH7-SW1
I think you probably want to create a custom subclass of a UITableViewCell as the UITableView will handle all the redrawing for you. In a custom UITableViewCell you can add as many subviews as you like.
Take a look at http://cocoawithlove.com/2009/04/easy-custom-uitableview-drawing.html.
UITableViews are subclasses of UIScrollView (or at least conform to their behavior), but you really want to let the iPhone handle the selective drawing/cell reuse for you that the UITableView provides.
You should use UITableView if it does everything you need.
However if your tableview cells are really complicated, or you want to enable paging on the scrollview, you should take a look at the PageContol sample code that Apple provides. In a nutshell, you watch for movement in scrollViewDidScroll: and load new "pages" just before they become visible. This method works very well in practice for arbitrarily long lists of pages.