I am using an AQGridView to display my data in a grid on iPad. Every cell is a UIView subclass and typically, there are 18 cells displayed simultaneously.
I would like to add a round corner to these cells, so I set the cornerRadius property of the relevant layers (i.e. the layer of the main UIView and of one subview). However, this results in performance issues and the scrolling is not smooth any more. When using other CALayer properties, such as shadowOpacity, this does not happen.
Are there any other ways to add a rounded corner (apart from using an image)? Or am I doing something wrong?
I also saw a major performance hit when using cornerRadius on the layer of a view that contained a UIImageView subview. Rasterization solved that problem: view.layer.shouldRasterize = YES;
It could be where you're placing the setCornerRadius call. Make sure it's somewhere that only gets called once, not, for example, in a drawRect method.
Related
I have a tableView. Instead of having multiple subviews in each tableViewCell , i have added one main subview which draws each of the other subviews in its drawRect method.
(I have read somewhere that this makes scroll animation look better. Also apple has a sample project CustomTableViewCell).
First , problem is when i changes the orientation of device, then drawRect does not call automatically. And each tableviewcell appears to be stretced.
I solved this by using
mainView.contentMode = UIViewContentModeRedraw
This solves the problem. Now when the orientation change is done, drawRect is called automatically .
But during the orientation change, the animation of rotating view still shows each tableview cell stretched. It is a very small thing, but still it is noticeable. Can anyone suggest something on this ?????
You can't redraw during animation (not easily, anyway).
Split the table cell into components again and setup autoresizing correctly. The animation will then animate only component positions and it will look fine.
Where did you read drawRect: would make scroll animation better? Did you have some problems with scrolling animation?
Edit:
IMHO There is no way how to fix resizing animations and keep the performance increase from using drawRect: instead of subviews.
I'm trying to make sure my UILabel's and UITextView's stay sharp when they exist within a UIScrollView. I came along the 'contentScaleFactor' property on the UIView class, it seems to work perfectly fine on custom drawing but UITextView's and Labels just refuse to redraw themselves at the right contentscale.
http://pastebin.com/PBjhjMbR
Maybe this is due that the actual views that draw the text are a subview of these classes?
You need to set contentScaleFactor recursively on all subviews and also call setNeedsDisplay on each view that you set it on to make them display at higher quality. I have also found that it is not worth setting it on a UIImageView because they won't render at higher quality anyway so there's no point in wasting memory by making their backing layers bigger.
I've got a pretty big UIScrollView (contentSize 8000 x 960) with a lot of small labels.
The labels are only added if you scroll to the area where the label belongs to. So, at first, the scrooling is smooth, but as more and more labels are loaded, the performance suffers more and more.
What's the best solution to keep the scrolling smooth? Is CATiledLayer the way to go? Or should the labels off the view should be hidden or something like that?
Thanks a lot for your help!
Stefan
EDIT:
I got a huge performance boost when drawing some objects instead of using views; but now, I've got another problem; if I draw directly onto the UIScrollView, everything performs great. But if I lay a UIView on the UIScrollView and draw on that, performance goes down again (both times calling setNeedsDisplayInRect: in scrollViewDidScroll:).
So hierarchy:
UIWindow
UIView
UIScrollView <== drawing here
works fine.
But hierarchy:
UIWindow
UIView
UIScrollView (size 8000x960)
UIView (size 8000 x 960) <== drawing here
performs bad.
Any ideas why? I need the UIView above because the drawing should be ABOVE some UIViews; so I place the UIViews in the scrollView and draw in the view above...
The label reuse is one of possible solutions. Sometimes it doesn't help a lot. When a new UIView appears the drawRect method will be called and that may cause problems with animation.
Sometimes the best solution is to draw your labels (I mean text) directly using Core Graphics without creating UILabel object or something else. The CALayer will increase performance, but there is a possibility that it will not help you a lot.
But first of all you should remember that views with alpha = 0 or hidden = YES will not be drawn at all, so there is no penalty for using them. Maybe you should try to hide unused ones before using Core Graphics.
The best way would be to have just a few UILabels and reuse them. But you'll have to implement - (void)scrollViewDidScroll:(UIScrollView *)scrollView and do some reusable logic there. Depending on case it might be easier to use a UITableView and transform it 90 degrees, so it looks like a scrollview. That way you can the build-in reusable logic of the TableView.
For others seeing this post, I was able to drastically improve performance and keep UIViews in a scroller without using a table by enabling each view's "shouldRasterize" property. This property renders the view as an image while the view is in motion, causing it to not need to be reprocess for each pixel it moves. So, if I have a UIButton called button, it gets enabled like this:
button.layer.shouldRasterize = YES;
Did u try something similar to UITableViewCell
dequeueReusableCellWithIdentifier
Using a reuseIdentifer to reuse the once allocated labels..
I have a UIToolbar in IB with a custom UIBarButtonItem that is set to an image. The image height is larger than the UIToolbar height. The image does not load for some reason. Attached is a screenshot.
You should avoid using subviews that are larger than the parent view - even if it does work and draws the view outside of the bounds, you cannot always count on it because the clipping is skipped for performance reasons and depending on the drawing order the overlapping part of the subview might be covered later. Second problem is that only the part within the frame of the superview is able to handle the touch events.
As to why you don't see your image, it's probably a different problem, I doubt it has something to do with it going outside the frame. Post your code to get more feedback ;)
I'm trying out this nice way of customizing grouped UITableViewCell backgrounds:
http://code.coneybeare.net/how-to-make-custom-drawn-gradient-backgrounds
I've implemented it in a test app and it works great, except for one thing... when rotating the device, the cell background is stretched, making the corners look distorted.
Is there any way to force a table cell to redraw itself on an orientation change? Do I need to use setNeedsDisplay somewhere?
(I've tried [cell.backgroundView setNeedsDisplay] in a couple of places just as a random guess... but that didn't work.)
Set backgroundView.contentMode = UIViewContentModeRedraw if you want it to redraw when the bounds change.
Additionally, do not override -isOpaque like the example suggests; I'm pretty sure that opaque-ness is backed by the CALayer property of the same name. Instead, set self.opaque = NO in initWithFrame:.