Can anyone explain the differences between these 2 methods? The docs for UIViewController explicitly state that viewWillTransitionToSize should be used for managing rotations, but clicking through to the UIContentContainer page, the willTransitionToTraitCollection method makes a confusing entrance.
I think I understand the conceptual difference between a size class change ( trait collection change ) and a size change, but I'm not sure which method to implement in which circumstances. Clarification from a UIKit wizard would be helpful!
Whenever you want to do something aa a response to a user rotating their device you should use viewWillTransitionToSize, if you do that you know for sure that your actions are executed as this is called every time your app's window changes size.
If you only want to take action when the trait collection changes, for instance if you have a certain collectionViewLayout set for a Compact size class and another you want to use for Regular you use willTransitionToTraitCollection.
If the trait collection changes then the size also changes. But it doesn't work the other way around. A portrait iPad and a landscape iPad have the same traits but are different sizes. Add multitasking to the mix and you have a whole variety of sizes that would map to just two traitCollection size classes.
I am currently developing an iOS app and I was wondering how to manage the UI elements. I am using a Storyboard to place my views and Autolayout to make everything resolution independent. If it helps, here's a bit of background on how I came up with this question.
Some Backgroud
I have buttons the represent piano keys and I later in code add a subview to these that draws the actual keys on them. I did this by creating #IBOutlets on the ViewController and susbscribed to the UIDeviceOrientationDidChangeNotification. This called a method that adds the subviews based on the current button frames to get the appropriate sized keys.
This worked fine when running in iOS 8.1, but if I ran the app on iOS 7, the frames of the buttons weren't updated to the new orientation by the time I got the UIDeviceOrientationDidChangeNotification, so everything was messed up in landscape. I did a little research (UIInterfaceOrientation not yet updated when UIDeviceOrientationDidChangeNotification caught in UIView) and it seems that a good solution would be to override the layoutSubviews method. Problem is, layoutSubviewsis a UIView method, and I am managing my buttons and UI in my UIViewController.
Impulsively I wanted to subclass my UIView, override layoutSubviews and from there call a method on my Controller to add the keys to the buttons correctly, but that doesn't sound right.
The Questions
My UI is managed by the UIViewController. But I need to update my views based on a method proper of a UIView. I assume, to respect the MVC principles, that my view should't now a thing about my controller, but then this brings up a few questions:
Who should be managing the UI?
Is my strategy wrong and should the
UIView hold the #IBOutlets to the buttons so that it can later
apply the subviews I need them to have?
If you read the background, do you have a suggestion for this particular situation?
I assume the complexity of this problem is relatively small and I don't need to setup notifications in NSNotificationCenter, but I may be wrong. I would really like to hear this is not the only solution.
Thanks in advance. I hope I was clear enough, but if you want/need any additional details on my particular situation, let me know and I will gladly elaborate.
if I understood the question correctly, your ViewController should be laying out the keys within it's view. A good, but not the only, place to do this is in viewDidLayoutSubviews which a method you can override on UIViewController.
Now if your views should maintain their internal layout. i.e if you buttons/keys have any subviews, you should update those in layoutSubviews on UIView as you mentioned.
Both methods will be called in response to changes in the bounds or center of your parent view.
As far as rotation changes are concerned, in iOS 8, you should use viewWillTransitionToSize:withTransitionCoordinator: or willTransitionToTraitCollection:withTransitionCoordinator:
depending on your needs.
I highly recommend that you write your layout independent of orientation. You should just use the containing view's bounds for reference and never hard code in any frames. For example perhaps one of your keys should be 1/56 the width of it's superview instead of a magical number for portrait and landscape.
I know this has been asked before, but none of these solutions work, and that's the reason of my posting. Please do not close before considering my case.
My plist already has UIViewControllerBasedStatusBarAppearance = false.
I have already tried applying deltas, but to no result.
Changing the top level view frame in ViewWillAppear (like self.view.frame) did not succeed.
I thought of increasing the view height (storyboard attribute inspector), in combination with deltas, but my top level view X, Y are disabled in storyboard attribute inspector.
My main view doesn't have any children views because I load them into main view either dynamically or load them from XIBs which are again shared by more than view controllers. These XIBs provide layout for both Portrait and Landscape. I don't know what approach is ideal for this kind of configuration, but I would like it better if solution lies along these lines.
This approach worked partially, but gave me inconsistent results.
What makes the solution tricky is the fact that I have to support all 4 orientations - this is something I handle in code via didRotate and willRotate delegates for my other views, but failing to do it for statusbar.
Please help...
Could this link be of any help?
You might have to use the new setEdgesForExtendedLayout: method to get this working consistently?
Also, have a look at these official docs if you haven't already done so.
I ended up writing my own function to shift my all subviews (remember, not top level views whose frame is fixated by IB).
It didn't spoil my work but imagine if this was the case for a very big project with so many screens, the limitations would have made it a nightmare.
OK so in my game I need the users to scroll between items, just like you scroll a web page in Safari. Is there any way to do that? If not, maybe scrolling them to the side, like you do in the spriboard? Thanks.
I am not really sure I have understood what you would like to do, but there is a cocos2d extension that seems appropriate to it: CCScrollLayer.
CCLayer subclass that lets you pass-in an array of layers and it will then create a smooth scroller. Complete with the “snapping” effect.
If you are looking for a generic scrolling within your view, I suggest this tutorial or this topic rom cocos2d list.
EDIT:
I have never done it, but I think it should be possible to scale the CCScrollLayer to the size you need.
Otherwise, you might change the contentSize of the layer, or even put the CCScrollLayer into a clipping node.
Anyway, I think that it is much easier to start from this and find a way to adapt it to your specific requirements than start from scratch.
OK, I think it's time to make an official place on the internet for this problem: How to make a UIScrollView photoviewer with paging and zooming. Welcome my fellow UIScrollView hackers.
I have a UIScrollView with paging enabled, and I'm displaying UIImageViews like the built-in photos app. (Does this sound familiar yet?)
I found the following project on github:
https://github.com/andreyvit/ScrollingMadness/wiki
Which shows how to implement zooming in a scroll view while paging is enabled. If anyone else tries this out, I actually had to remove the UIScrollView subclass and use the native class otherwise it doesn't work. I think it's because of changes in the 3.0 SDK relating to how the scroll view intercepts touch events.
So the the idea is to remove all the other views when you start zooming, and move the current view to (0, 0) in the scrollview, updating the contentsize etc. Then when you zoom back to 1.0f it adds the other views back and puts things all back in order.
Anyway, that project works perfectly in the simulator, but on the device there is some nasty movement of the view you are resizing, which looks like it's caused by the fact we are changing the contentsize/offset etc. for the view being resized. You have to do this view moving otherwise you can pan left through the whitespace left by the other views.
I found one interesting note in the "Known Issues" of the 3.0 SDK release notes:
UIScrollView: After zooming, content inset is ignored and content is left in the wrong position.
This kind of sounds like what is happening here. After zooming in, the view will shift offscreen because you have changed the offset etc.
I've spent hours on this already and I'm slowing coming to the sad realization that this just isn't going to work.
Three20's photo viewer is out of the question: it's too heavy weight and there is too much unnecessary UI and other behaviour.
The built in Photo app seems to do some magic. If you zoom in on an image and pan to the far edges, the current photo moves independently of the photo next to it which isn't what you get when trying this with a standard UIScrollView.
I've seen discussion about nesting the UIScrollView's but I really don't want to go there.
Has anybody managed this with the standard UIScrollView (and works in the 2.2 and 3.0 SDK)? I don't fancy rolling my own zoom + bounce + pan + paging code.
UPDATE
I deleted my previous answer because of the news below...
Big news for those who haven't heard. Apple has released the 2010 WWDC session videos to all members of the iphone developer program. One of the topics discussed is how they created the photos app!!! They build a very similar app step by step and have made all the code available for free.
It does not use private api either. Here is a link to the sample code download. You will probably need to login to gain access.
Check This
And, here is a link to the iTunes WWDC page:
Check This
I've written a simple and easy to use photo browser called MWPhotoBrowser. I decided to create it as Three20 was too heavy/bloated as all I needed was a photo viewer.
MWPhotoBrowser can display one or more images by providing either UIImage objects, or URLs to files, web images or library assets. The photo browser handles the downloading and caching of photos from the web seamlessly. Photos can be zoomed and panned, and optional (customisable) captions can be displayed. The browser can also be used to allow the user to select one or more photos using either the grid or main image view.
You say you've seen discussions of nesting UIScrollViews but don't want to go there - but that is the way to go! It works easily and well.
It's essentially what Apple does in its PhotoScroller example (and the 2010 WWDC talk linked to in Jonah's answer). Only in those examples, they've added a whole bunch of complex tiling and other memory management. If you don't need the tiling etc. and if you dont want to wade through those examples and try and remove the bits related to it, the underlying principle of nesting UIScrollViews is actually quite simple:
Create an outer UIScrollView and set its pagingEnabled = true. Add it to your main view and set its width and height to your main view's width and height.
Create as many inner UIScrollViews as you want images. Set their width and height to your main view's width and height. Add them as subviews to your outer UIScrollView, each one next to the other, left to right.
Set the content size of the outer UIScrollView to the total of the widths of all the inner UIScrollViews side by side (which is equal to [your main view's width]*[number of images]).
Add your images' UIImageViews to the inner UIScrollViews, one UIImageView to each inner UIScrollView. Set each UIScrollView's content size to each UIImageView's size.
Set min and max zoom scales for each inner UIScrollView and set each of the inner UIScrollView's delegate to your View Controller. In the delegate's viewForZoomingInScrollView, return the appropriate UIImageView for the UIScrollView that is passed. (To do this, just keep each of the UIImageViews in an NSArray and set the corresponding UIScrollView's tag property to the index of the appropriate UIImageView. You can then read the tag in the UIScrollView passed to viewForZoomingInScrollView and return the appropriate UIImageView from the NSArray).
That's it. Works just like the photo app.
If you have a lot of photos, to save memory you can just have two inner UIScrollViews and two UIImagesViews. You then dynamically flip between them, moving their position within the outer UIScrollView and changing their images as the user scrolls the outer UIScrollView. It's a bit more complex but the same principle.
I did some playing around with the native Photos app, and I think I can say with confidence they are using a single UIScrollView. The giveaway is this: zoom in on an image, and pull to the left or right. You will see the next or previous photo. If you tug hard enough, it will even page to the next photo at 1.0f zoom. Flip back and the previously zoomed photo will be back to 1.0f zoom as well.
Obivously I didn't write Photos.app, but I'll take a wild guess at how they did it:
A single UIScrollView and a single UIScrollViewDelegate
Populate the UIScrollView with UIImageView children
Listen for scrollViewDidScroll:
Do some math and figure out what page you are currently on
Listen for viewForZoomingInScrollView:
Return a different view depending on the page index
Listen for scrollViewDidEndZooming:withView:atScale: and optionally do some anti-aliasing, etc based on the content
If you decide to try that out, let me know how it works out for you. I'd love to know how you finally end up getting this to work. Even better, post it to github.
I did some playing around with the
native Photos app, and I think I can
say with confidence they are using a
single UIScrollView. The giveaway is
this: zoom in on an image, and pull to
the left or right. You will see the
next or previous photo. If you tug
hard enough, it will even page to the
next photo at 1.0f zoom. Flip back and
the previously zoomed photo will be
back to 1.0f zoom as well.
This is wrong. I'm using nested scrollviews, and getting exactly the same effect. If you're using some memory management scheme (which I had to start using... my page number is fairly high ('bout 50 each in 2 scrollViews)), then you can use a mechanism similar to whatever you have triggering your page loads / unloads to trigger a zoom reset for the pages -1 and +1 from the current page.
I suspect that apple sets this off as soon as the previous pic has disappeared.
What I don't understand is how to achieve smooth scrolling between pages - there's always a very short hang at the moment of transition. Do not get it. I've gotten pretty deep into fixing it - NSInvocationOperations were my first stop, then I made a reusable views queue for the page views (which retain their image views)... still this durned hang.
I only have one NSOperationQueue running, and I've tried fiddling with the max number of concurrent operations. My thought was that the main thread was getting clogged by competing Queues, or maybe even one queue trying to do to much... still, the hang.
I even tried creating super low-qual versions of my media, in case that was the problem. With each image weighing in at around 10k (these are jpegs, mind you)... you guessed it. The hang's still there.
I'm pretty much resolved to do what I've done before and use TTPhotoViewController from Three20. I've spent some hours swimming through that code, and it's always a great education. At this point, though, I would really like to know where the heck this hang comes from, if only so I can spend my can't-sleep hours wondering about something less brain boiling.
sure would be nice if apple built an image viewer like the photos app into the SDK for us to use. I'm currently using three20 and it works great. But it is a lot of extra stuff to carry around when all you really want is the photo viewer.
i write a code for that , and can be as reference
load current view scrollview and imageview ..
and for the screen next to the current view , only imageview
remove all view when current page load to save memory , so good for many photo project
use tag to differentiate different scrollview
_xxxxxxx
the download link click here
Take a look at https://github.com/facebook/three20/blob/master/src/Three20UI/Headers/TTPhotoViewController.h Not sure if that's what you are looking for