Is there an equivalent of getGlobalVisibleRect in Objective-C ? I'm trying to get the visible rect of a subview that could be obscured by other views above it in the parent view hierarchy but it seems very tedious as some other similar question(s) on SO indicate. The desired implementation is to auto play some content in an AVPlayer view if a certain percentage of the AVPlayer view is visible on screen, similar to how Facebook auto-plays video media in one's feed. However this seems convoluted with having to firstly get the root view and recursively check with its subviews and their subviews and their subviews... and do a CGRectIntersectsRect with the player view & every subview above it. Surely there's got to be a simpler way to do this or am I headed down the path of recursion?
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I am trying to build an iOS app that will have the structure of Facebook's feed:
A vertical collection view that will have cells. Each cell will consist of image and text.
In fact, I am building my app with the help of this video by LetsBuildThatApp (this guy rocks by the way).
Currently, I am able to touch the image and animate it to full width, and also pan to dismiss it if velocity on Y-axis is more than a specific threshold.
What I want to achieve after that is to also be able to pinch/double tap to zoom. Like this:
I searched around and found some great articles on how to use UISCrollView to zoom. [Article1, Article2].
The problem is that I use autolayout to perform animations but these articles either use Storyboards or frames to position the image in the center of the scroll view [or at least this is how I understand it]. And also they don't involve any animations to start with.
Also, I don't want to present or push a view controller onto the navigation controller stack. I would rather animate the view on top of the base view as I do now.
Any idea on how to achieve this?
Thank you in advance!
I have an iPad app similar to the iPad Keynote with a narrow overview on the left and a paged UICollectionView of my "slides" on the right. The collection view is using the default FlowLayout. Some of these slides are standard PDFs and some are embedded UIViewControllers that have been scaled (with a CGAffineTransform) and embedded in the cell. I'd like to smoothly animate the overview sidebar offscreen and zoom the current page cell to fullscreen. The collection view should allow paged swiping at whatever size. I'm using storyboards and autolayout.
I think I need to simultaneously animate about three things:
The collection view constraints (to the sidebar) to enlarge/shrink it
The flow layout's sizeForItemAt: value
The CGAffineTransform on the embedded view controller.
I have some pieces working (a single embedded View Controller "slide" that scales correctly) but cannot get the collectionView/cell resize dance to work correctly. The cell resize animation is jerky, or ends up with the wrong offset, or works for the leftmost cell but not for other cells.
I've tried most of the suggestions in the answers to this question but with no convincing success. I can't believe it's impossible but at this point I'm considering the smoke and mirrors approach of animating a static slide and hiding it after the animation completes. The attached video - ignoring the glitches - illustrates the kind of effect I'm after:
It's worth noting, on close inspection, that Keynote cheats somewhat when it comes to swiping between slides in edit mode, and manually manages the next slide sliding onscreen, so probably doesn't use a UICollectionView.
Has anyone done anything similar, or have any suggestions for things to try?
I managed to solve this. There's a proof-of-concept GitHub repo here.
There are a few moving parts:
There are two pieces of UIView scaling code. I suspect these could be combined with suitable delegate references as the nested view controllers are embedded. The first piece scales (statically) correctly when the Collection View cell is created. The second is an animated scale/translate when the sidebar size is changed.
I added a FlowLayout subclass to remove flicker as the collection's layout is invalidated during scaling.
The sidebar-related transform in the top-level VC uses most of the tricks in the book - invalidateLayout(), performBatchUpdates(...), layoutIfNeeded() etc. as well as animating the contentOffset to the correct value. Some manual tracking of the correct page/slide is required.
There's still a slight flicker occasionally at the start of resizing. This may not be an issue with my particular colour-scheme which will be black on dark gray. Bonus points if anyone can suggest how to track this down or alleviate it.
I'm trying to do a custom layout like the Chanel app you can find the app in the Appstore.
https://itunes.apple.com/us/app/chanel-fashion/id409934435?mt=8
I know they are using an UICollectionView, but no clue how to start.
The interaction feels like a tableview mixed with a paginated scroll. When you scroll the elements grow, and the first element position itself at the top.
Start with dragging & positioning just one UIView. See UIGestureRecognizer docs and look for existing examples of movable views. You'll need an UIPanGestureRecognizer to move the view.
Resize the view depending on its Y position.
Create & position an image inside that view depending on the view size using a couple autolayout constraints.
Note that Chanel app has different constants for these constraints. With a minimum view height, one image's top is 80% height, for another image it's 90% height. Make sure you can manipulate constraints from code (I think it's a good idea to create everything from code there, XIBs are not very flexible).
Make the view "anchoring" to certain points (e.g. top = -75%, 0%, 75%, 90% from what I see in the Chanel app) when you stop moving it. Just find the nearest one and animate the view to it.
Once you did it with 1 view, move all your work to an NSView subclass (if it's not yet there) and create a collection of these views.
You can create UICollectionView, but I'd rather do it with a simple NSArray: I actually don't see a reason to use UICollectionView here; it's a very simple structure. Anyway, you write your own gesture recognizer (don't you? I can't see another way) - so what's the point to use UICollectionView? If you want to expand the app functionality some day, UICollectionView will unlikely help you with that. Well, it's my hypothetical approach, you can find another one while working on that.
Position other views while you're moving an "active" view. Do it by hand, without any UIScrollViews.
Write a function that reflects the Y position of the "neighbor" views while you moving one. It should "slow down" to the bottom of screen.
I'm using a UICollectionView (with horizontal layout) to manage a collection of images. The view controller that manages the collection view has the bottom toolbar visible with a play button to start a slideshow of the images in the collection. My question is what is the best way to implement a slideshow that involves a collection view? My initial thought was to try to make the collection view changing the visible cells with a UIView transition (transitionFromView or transitionWithView) with a cross dissolve option but I didn't get the effect I was expecting (maybe something wrong in my code). The other idea I had was to simply add a subview to the collection view to handle slideshow. This subview would have access to the data source and be able to iterate through the images. Don't know if this last option is a good way to approach the problem. Anyone has ever tried this and/or what would the recommendation be to solve this problem?
My idea is no need of collection view. In scrollview place imageview which display images. In timer Change the offset of scrollview. so it looks like automatically images are changing as like slide show.
I have created a small app using a ScrollView w/ paging and a series of UIImageViews each representing a page. It acts similar to the Photos.app.
I want to be able to pan and zoom individually for each image (page of a scrollview).
What would be the most sound approach to do this? Should I replace the UIImageView page with a scrollview with a UIImage inside it? I would then have a main scroll view where each page of the scrollview had a scrollview with an image inside it that could be pinched,etc.
It seems like a messy approach. I am looking for a clean approach. Any suggestions?
Well, as far as I know the approach you suggest is the way it is done. I have used this to create a PDF viewer and once everything is in place it doesn't feel too messy.
You might want to use CATiledLayer as your inner (per-page) scrollview's layer (instead of CALayer) if these images you have are really big (which could well be the case since otherwise zooming in on them would not bring you much but pixelation, but this is just an assumption on my part).
Checkout UIPageViewController. This controller manages a view controllers for each page and transitions between them using effects like page curl or scroll.
In your case you would create a view controller that manages a scrollview for zoom & pan for each page.