I have a particular app that, because of the navigation structure, leaves me unable to use normal UINavigationBars with translucency, so I've chosen to try and use iOS8's UIVisualEffectView with Blur.
This solution mostly works, but there is a very noticeable flickering effect that occurs when the UITableView beneath this blur view is scrolled around. As the edges of an image or colored rect pass underneath the blur view, there is a significant amount of flickering that occurs.
Has anyone experienced this? Anyone know how to solve this problem?
My implementation is simple, I dragged a UIVisualEffectView onto my view controller and constrained it to top, left, and right screen bounds, and added a height constraint of 64. Beneath that is just a UITableView with some images and text.
"I assume that what’s not under the view is not being taken into account to compute the blur. It is likely being extrapolated (by padding the image by mirroring, replicating, wrapping, etc… as you would do to minimize boundary effects on any convolution). But this creates an undesired visual jump in many cases.
If you want to minimize this artifact, just make the
UIVisualEffectView bigger than your view. A few pixels will suffice,
the blurring kernel is not that big anyway. And make your view to clip
to bounds."
Reference: https://medium.com/#imho_ios/avoid-artifacts-on-uiblureffect-edges-c30e737c21fb
This worked for me, at least eliminated the bottom flickering in the Navigation Bar. However, it did not work at the top. I believe that is due to view (maybe UIWindow?) clipping against - in my case - the tableView.
UPDATE:
It seems the bug are fixed in iOS 9.0 and later.
I make an uiview which alpha is 0 and add blurview as subview of that. So i can minimize that flickering problem also can hide/show or rounding corners it with animation.
Related
I have a UIVisualEffectView with a UIBlurEffect effect as a pinned UICollectionViewCell in a UICollectionView.
The blur is masked with an icon so that the icon appears in a subtle shimmery way, responding to whatever it is drawn on top of.
The effect is on top of the collection's background. As it stays pinned and the varying background scrolls underneath, it gently changes to reflect the background and looks very nice.
However, except for the collections's scrolling background, most content is drawn in front of the blur effect. This is necessary because that other content is more important and shouldn't be obscured.
Even though it is behind the more important content, I'd like the effect view to reflect the content that is scrolling in front of it. Any suggestions for how this might be made to work?
Ideas:
Could I grab a chunk from the previously drawn frame and draw this under the effect view? How would I do that?
Could I render the whole collection view, apply the blur, and then render everything that should be on top of the blur a second time? How can I make that efficient?!
Thanks.
I went with a slightly refined version of the second option.
I added some duplicate cells to the collection view that are rendered behind the blur, and then also in front. I've only done this for one of my cell types with lots of colour in it. It works pretty well.
If you have a better approach I'll happily assign you the correct answer.
I have subclassed and am using UIPopoverBackgroundView in order to make custom appearances for my UIPopoverControllers. Everything seems to work great so far, the popover draws well and looks the way I expect it.
The issue is that, when my popover is left open for a period of time with no activity, the border will often suddenly be drawn wrong. This specifically seems to only happen when the popover contains a scrollview/tableview which is larger than the popover (i.e. it is scrollable). It also doesn't happen every time, but if it does happen, it occurs in less than one minute of inactivity. If I take a screenshot, the issue is not visible (despite it clearly being seen on screen) so I can't provide any images of the issue unfortunately.
Does anyone know of any reason why the border would be drawn incorrectly after several seconds of inactivity and how to fix the issue? I can provide snippets of code if necessary, though I'm fairly certain everything is right (and equivalent to the many examples I've seen online). I also do not resize the popover at any time during the inactivity (I do resize when initially displayed to fit the content up to a maximum size).
Since I can't take a screenshot to demonstrate the issue, the best I can do is describe it. It appears as if the border in certain areas is drawn at the wrong size (as in, part of the right edge is being drawn in the middle of the popover; NOT that the border itself is too wide, but rather that the area the border should be bordering is wrong). The area along the actual edge is still there, but is lacking it's layer effects (I have the backgroundView using a border and rounded corner layer effect to give it a nice rounded white edge, emulating the same appearance as the default background view, just a different color). Removing the layer effects does not prevent the issue though. Sometimes it's only a part of the right edge which is drawn incorrectly, sometimes part of the bottom edge is also affected. I can't seem to find any correlation as to when or how this happens (though it is frequent), nor to which edge is affected (though I've never seen it affect the top or left edge).
Does it only happen in the simulator or also on a real device?
This specifically seems to only happen when the popover contains a scrollview/tableview which is larger than the popover (i.e. it is scrollable)
Do you resize the scrollview / tableview in this case? Try adding a UIView inside your UIPopView that would be the container.
I am triggering an iOS animation to move some elements around on my screen, and when I do so, an area at the bottom of the screen (away from where I think I'm doing the operation) changes shade slightly. When I turn on 'show blended layers' in the iPhone simulator, it's clear that at the beginning of my animation, something starts overlaying that area, but I cannot figure out what. The view that I'm adding to my screen is a composite view, including a scrollview and an overlay -- something in there is overflowing the bounds it should be in, and I can't figure out what. The simulator obviously knows what it is -- it's happy to color it red for me as a blended layer -- but I can't get it to tell me what layer is being blended so I can fix it. How do I do this?
ETA: If I turn on clipsToBounds on the inserted view, my problem goes away. But I'd still like to know how to identify layered views when I'm trying to debug. Is there a way?
Try animating it all, but each time hide one more subview until one moment, when a subview is removed and problem is no longer visible - You will know which view is faulty.
Better is to go [view subviews] - to really access them all.
If you look at the button/label titled "Address" you'll notice a little speck of white in the corner. This speck of white only occurs when the user starts scrolling the tableView, which is located underneath the searchbar.
I can only guess that the modal border kills all transparencies while scrolling.
This is an iOS issue with regards to scroll view and is seen in many places - no solution other than you reducing or creating some offset for the tableview.
this artifact could be caused by a variety of different things. The first things I would check when seeing these things is that all of the UIViews (and there subviews) that overlap this area
A. Have a background color with an alpha value of 0
B. Have "Cear Graphics Context" turned off in Interface Builder (or corresponding flag in code)
I have a UIScrollView over an image at the bottom of my app that acts as a dock with icons that can be scrolled through horizontally. Instead of the harsh edges of the UIScrollView, I would like the icons to fade out for a more aesthetically pleasing look. Being new to iOS development, I don't know if either of these would be valid options:
Create a faded image to use as an overlay on the scrollview so the
icons only appear through the visible portion.
Actually change the
alpha of the images based on their distance from the center (or from
each edge).
I suspect the first idea would be the most simple, but I'd like to throw this out there for any other ideas.
Note: I did see this tutorial, however that technique assumes that the background is a solid color. If I were to do it programatically, I would probably need to fade the individual images.
You can definitely implement something along the lines of #2. It'd be something similar to what the tutorial describes. The alpha transition however won't be as smooth as using the gradient layer mentioned in the tutorial or using an image since the entire icon would have the same alpha. How much discernible the difference is depends on the size of your icons. Smaller icons, very few will be able to tell the difference. Larger icons the difference would be quite clear.
You'd have to implement the
(void)scrollViewDidScroll:(UIScrollView *)scrollView
method in your scroll view's delegate class. This method will get called every time the scroll view changes the location of its content. In this method you can call its subviews and adjust their alphas as required. To optimize it a bit instead of calling the alpha adjustments on all the elements you can just update the subviews which are still partially/completely visible.
EDIT: to figure out which views to adjust you'll use the contentOffset property of the scrollView that gets passed as a parameter in the above method.