I've been looking around here and seeing lots of questions that seem related, but I haven't found anything that's exactly what I need.
I have three UIViews that are animating inside a custom viewController. I want there to be a static background inside the viewController that is only revealed within the clipping bounds of the UIViews.
It's kind of like spotlights on a prison yard: the background should stay in one place, but as the spotlights move you can see different parts of it. Except that I don't need circles, regular old UIView frames are fine.
For instance, it seems like what I need is in the answer to this question: How to achieve dynamic UIView masking?
...the answerer provides a link to a page that shows how to statically mask an image, and then the answerer says "But personally I think i would make 2 UIImage views and crop the content of the draggable UIView"--without any info on how to do that.
How do you do that?
Related
I want the background image to only be visible where the individual cells are, so as you scroll it reveals different parts of a fixed image underneath. It's basically the opposite of a common tableview with opaque cells over a background, if that makes sense.
I still want the cells to be rendered normally in addition to their edge serving as a mask boundary, since they'd have text and other subviews that aren't just for masking.
I can't find an example, but I've seen this effect before done using CSS and it looks nice. It's not incredibly complicated, but I can't seem to figure out an efficient way to do it in UIKit.
I'm making simple number coloring game (like sandbox, pixel art, unicorn, etc) and came across a problem. I tried various methods of filling rects in the screen.
At first i created a backgroundView(a simple UIView) which had 2500 subviews(also UIViews), each one had size = (CGSize){50,50}. Added a tap gesture recognizer, detected which view should be filled, and simply changed the background color of that view. But when i placed the backgroundView in the scrollView, the scroll and zooming were awful.
Tried same thing but this time each rectangle was a CALayer. So a backgroundView, which had 2500 sublayers(each was a CALayer with 50,50 size) - zoom and scroll was also awful.
Tired to use custom drawing with overriding drawRect method in UIView subclass or drawInContext in CALayer subclass(i was filling rects with CGContext), this time problem was also caused by the zooming and scrolling. Because i needed to update every rect when user zooms, it was triggering a lot of drawRect calls, and performance was also bad.
Any thoughts how can i fill rects in the screen ?
Explanation
Yup! Adding 2,500 tiny UIViews to a scroll view can destroy performance. I wouldn't use that approach, but if you do, at least make sure that subview_N.opaque = YES; on all subviews to disable compositing.
The CALayer approach that you described is basically the same as the UIView approach because views are backed by CoreAnimation layers (see -[UIView layer]).
The best options for drawing thousands of rectangles to the screen on iOS without decimating frame rate, is to use one of the following approaches:
Draw directly using CoreGraphics
Draw directly using OpenGL (extremely involved)
Use a layout engine such as UICollectionViewLayout
Now, you said you had tried overriding -[UIView drawRect:], but you didn't provide any example code for us to checkout. Please update your question with actual code for method #3 if you want more specific feedback. It's very likely that something is wrong with the drawRect code you created. CoreGraphics can definitely draw thousands of squares on screen without dragging frame rate down that badly.
One Solution
I recently released a project, YMTreeMap, that draws thousands of rectangles into a UIView to create financial TreeMaps. It's in Swift, not Objective-C, but the underlying concepts are the same. For this, I created a custom UICollectionViewLayout that lets Apple's well tested UICollectionView class handle the nitty gritty of selective drawing, zooming and animation.
The example UIViewController code in the YMTreeMap project shows how to draw thousands of colored rectangles to the screen if all you know is their location and size. This sounds like what you are doing. Since you're also scrolling and zooming, this solution might be perfect for you because UICollectionView has native support for both of those.
Is there a way to find all UIView items positioned over a given point? I have a Swift project with a custom keyboard. The footer has four buttons and the taps are not working. I think perhaps there's an overlapping view which is higher in the Z-order so it blocks the taps, but transparent so I can't see it.
I didn't write it so I'm not sure about what view might be doing this. If I can pick a point and find all views that cover that point then I could use reflection to find out which of our extensions of UIView it might be.
Thanks
Mike
I want to implement scrollable button list which are displayed inside popup. I would need some kind of masking, but buttons should also work inside mask. Any suggestions how to do it?
It is possible to achieve this with CCMask class but this is pretty slow way to do it as mask has to be applied every update.
If you use this class you will also loose button detection so you will have to play with touch detection. You will also nead a lot of tweaks to position mask & objects exactly where you want.
When you will finish everything it will not be as good as you thought it will be .. The feeling of scrolling will just not be OK, since there will be masking lag ...
It is better to hide hidden parts of scrollable items with some kind of "window" images
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.