I have a very tall cell with massive text content in it. Reveal shows it's height is 7000+. When scroll during that cell(it's so tall that will take a while) the tableView's scroll performance is particularly bad.
After Time profiler the tableView scroll. It shows the drawRect: method of one of subviews cost the most. That subview is a third party custom textView. I breakpoint the drawRect: method the backtrace like so:
And it turns out the drawRect: is called many times when scroll during that very tall cell. So what cause the drawRect: is called during scroll inside one cell??
Having a quick look at the custom text view you linked, it looks like -setNeedsDisplayInRect: is called whenever the text view frame or bounds is set, and on touch events.
Looks it's the UIResponder touch methods that are the culprit, in which case setting userInteractionEnabled to NO on the SETextView should solve the problem. Of course, you may well want to keep interactions enabled on the text view, but I'm sure you can come up with something!
Related
Is it possible to let UITableview move up/down whole cell height just like date picker (not stop between the cell top and bottom)?
The class UITableView is a subclass of UIScrollView.
This means that, if the object you specified as your table view's delegate also adopts the UIScrollViewDelegate protocol, that protocol's methods will be called on it whenever the relevant scroll events happen on the table view.
You can use that timing to "fix" the table view's scroll offset in just the right way to simulate the snap-to-row-bnoundary behaviour you're after.
Some examples:
scrollViewDidEndDragging(_:willDecelerate:): Tells the delegate when dragging ended in the scroll view.
scrollViewDidEndDecelerating(_:): Tells the delegate that the scroll view has ended decelerating the scrolling movement.
Which methods to implement, and what exactly to do in their implementations, will depend on what effect you want to achieve. Play around and see.
I'm creating my views programmatically. I have a UITableView in my UIViewController subclass that I want to add a scrolling subview to that is not a cell. I want to add some text-based subview to the UITableView that scrolls with the table and starts out above y=0 so the user will only see it if he pushes the table down. That is, it should reside above the first section of my table. If it helps for visualization, I intend to make something similar to those "scroll down to refresh" features and want some indication to the user that scrolling down causes a refresh. Is there any way to do this without something messy like using another UITableViewCell to represent it or abusing the UITableView delegate methods to move a view around whenever the user scrolls?
Simply using [tableView addSubview:] in my viewWillLoad only makes it appear for a split-second then disappear once the table data is loaded. This seems weird to me because UITableView is a subclass of UIScrollView, which is meant to hold other views in it. Using [tableView.backgroundView addSubview] does nothing.
P.S. Why not use a UIRefreshControl for this? I'm still undecided but leaning towards not using one because I don't like how slow that spinning wheel "feels" when the refreshes are usually very very quick. I've been looking at other options like flashing the background subtly and only showing a wheel if it's taking a longer time than usual.
I You can implement pull to refresh with only a table view
To do this using the scroll view delegate, since tableview is a subclass of scroll view.
Set view controller to be the tableview delegate and implement
(void)scrollViewDidScroll:(UIScrollView *)scrollView
When scrollview content offset y value passed a point, add a label to the viewcontroller.view not tableview. When you scroll back or release, remove the view.
You might also be able to add label to the table view and set the frame origin to negative y value, so when you pull the label will move into view (Never tested this do might not work)
I am following this excellent small tutorial about drawing on screen in the layer of a UIView (subclass).
http://spritebandits.wordpress.com/
It just works.
There is just one thing. I placed this view as subview of a UITableViewCell which, naturally, is displayed as part of a UITableView.
I guess I would have the same issue when I would place it within an UIScrollView. (UITableView inherits from UIScrollView anyway)
Touches are triggered by my painting view as long as their related movement is horizontal. As soon as I move the finger kinda vertical, even partly, then the UITableView takes over and scrolls the table.
Is there any proper way of stopping the Table to taike control of the touches while the touch is actually within my view?
If it is of importance: I am using storyboard. The cell is a prototype cell with its own subclass of UITableViewCell.
I've implemented this using the same class "Canvas" you're saying and also inside a UITableViewCell. But I didn't use the entire cell for drawing, only a UIView inside of the UITableView as a subview.
I reached the whole user experience by activating and deactivating the UITableView scrolling when that UIView (subview of the cell where I allow the drawing) fires touchesBegan or touchesEnded. So when they touch/move inside the UIView, they're drawing. When it's outside, they're scrolling. So they can't scroll on the UIView because they will be drawing.
The problem in your case is that since the whole cell is the view for drawing, the user cannot scroll in this concrete cell because it's the drawing one.
Hope this will help.
I dont have an answer for that. But there is essentially a work around.
You could get the user in to a drawing mode, where the scrolling for a UItableviewcell is disabled and then
once the user is done with drawing, you could enable scrolling again.
Inclusion of a button anywhere on the screen would help you switch modes.
I've created a UITableVIew and it is a subview of a UIView. There are three issues that i'm having and it is only occurring on iOS 4 devices:
1) The table doesn't bounce when the view hits either the top or bottom of the table while scrolling. The vertical bar doesn't shrink either, it feels sticky and it is very much acting like an Android table view. I've tried enabling the bounce property but that doesn't make any difference.
2) The horizontal scroll bar appears when the view is scrolled down to the bottom of the table. This shouldn't appear since the table view's contentSize has been set correctly. It does eventually disappear when the contentSize is set 20 pixels less than what it should be.
3) I can't scroll to the bottom of the footer view, and only half the footer view is visible.
I've added a UITableView as a subview to other views throughout my project and this has never occurred, and so i've copied the way that I create other UITableViews, but still no luck.
Any suggestions would be greatly appreciated.
Thanks,
Ankur
I worked out the problem. The problem is a little strange, although i had a feeling that the way i was coding was a little messy.
I am subclassing a View, and the parent view has a layoutSubview method, which is only calculating and setting the frame for a table view subview. In the subclass, i had to override layoutSubview for the same reason as the values for the table view's frame need to be different. This means that the table view's frame was being laid out twice, once by the parent class and a second time by the subclass. It seems that iOS 4 doesn't like this, and i should only set the frame once per subview per layoutSubview call.
Now i've created a layoutTableView method, which is called from the parents layoutSubview, and i've overridden layoutTableView in the subclass. Therefore the table view's frame is only being set once.
I have two Scenes in my Storyboard that are nearly identical. Both are UITableViewControllers. Both have header and footer views. The header views have a UISearchBar and the footer views have a UIView that contains a UITextField. Each have only one prototype cell. One is prototyped as a "Basic" cell and the other is prototyped as "Right Detail" cell.
Here's the problem. When I click the UITextField in the footer view on the first scene, the table resizes automatically so that the bottom of the table is at the top of the keyboard. This allows me to scroll the table up so the footer view shows and the user is able to see what they're typing. The other scene will not automatically resize the UITableView so the UITableView cannot scroll the footer view to where it can be seen and the UITextField is hidden under the keyboard. I can't even manually scroll the table far enough since the footer is always at the bottom of the UITableView.
A little added info. The scene that works has many rows of data while the one that doesn't work only has a couple. I tried adding a number of rows until the table had enough to enable scrolling and it doesn't fix the problem.
I have checked everything I can think of and I can't see anything that would allow one of the views to let the UITableView to automatically resize to work with the keyboard and the other not. I must have overlooked something but I can't seem to find it.
Any help will be greatly appreciated!
Rob
I thought this problem was caused by copy-and-pasting from one view to another, but I had the same problem once I'd (in theory) fixed it.
The answer for me turned out to be simple: I hadn't called [super viewWillAppear:animated] in my UITableViewController subclass' viewWillAppear: implementation. Make sure you've got a call to the superclass' method and hopefully the problem will go away.
I am guessing the frame of the tableview is not being resized to the smaller size in the second case.
Print out the frame and content sizes in both the cases once its loaded, that should help you see if there is an issue.