I'm trying to workaround a long-running bug in Apple's SDK here, but I can't see how to achieve it without huge amounts of code.
Here's the bug:
Create a view.
Put another view inside it, with an origin ANYTHING except (0,0).
Configure the subview to resize to fill
...then, at runtime:
4. Set the superview size to zero
5. Set the superview back to ANY non-zero size
BANG! Apple's SDK goes haywire, resets the origin of the subviews, loses all ability to tell up from down, etc. (seems like the programmer "Forgot" to include a variable to record what the spring/strut-size was before it went to 0).
I've heard this bug has existed in OS X for 5 years or so, and Apple still hasn't fixed it. What I would like is some way (any way!) of working around it, without re-writing Apple's entire springs/struts system and implementing it properly, without the bug. Unfortunately, I can't even find the original references to the OS X bug that someone showed me previously.
EDIT:
...I have a resizing "drawer" at the bottom of the screen that has to shrink to small height. The problem is subviews "collapsing" all down to origin 0 (amongst other things) at the drop of a hat (technically: they're reducing their origin.height, but not re-increasing it).
The best solution I have found is to limit your minimum window size so that none of your views can ever hit zero size.
EDIT: an hour later, the collapsing behaviour has returned, without me touching the source files. I'll use source-control to double-check, but I believe all that happened is I added other files to a different part of the view-hierarchy and re-built. Argh!
(what follows SEEMED to work, but is now failing again, in the same way)
Hmm. So, I had two UIVC's on one screen. Refactoring so that I only had one made the resizing bug vanish. It seems to be a bug in the UIVC layout code.
NB: I had the idea this might be a problem because I know Apple currently advises you to only have one UIVC on screen at once with iPhone, even though this means you have to ignore their MVC architecture for complex apps. So, technically, they warn you away from this. But, at the same time, I'm now unable to use the MVC stuff for this code.
The following worked (for my current example - may not be universal!).
HOW:
If you're adding any UITableViewController instances ... give up. You'll have to re-implement that class yourself
Find my subviews that were in UIVC instances, and change the extended class in the UIVC header from "UIViewController" to "NSObject"
Move all code from viewDidLoad to init (remembering that "init" has special rules about first few lines etc)
Replace the instantiation of that UIVC from "[[vc alloc] initWithNibName:nil bundle:nil]" with a plain "[[vc alloc] init]"
Another potential workaround (that works in my current situation):
The only View I have right now that MUST have a non-zero origin and MUST resize-to-fit is a UITableView.
Apple has a special feature of letting you put any view as a "table-header".
So ... I've taken all my other components, stuck them in a large view, and made that the table-header view.
The downside is that they now scroll off the top when you scroll the table, but it allows me to give the table a zero-origin, working around the SDK bug.
Related
I have searched multiple discussions/examples for hours re UITableView using UIRefreshControl, and found most predate iOS11, and fall into one of two basic implementations, neither of which are working for me. Either I pull down and it won't finish (i.e., control slides with spinning wheel, and swiping up merely bounces it back down - yes, I'm using .endRefreshing); or it successfully completes but not before flashing large title on top of control (with original title still pulled down), and table cells jump up and down.
I am using Storyboard, and checking the enable box. I am placing the code in ViewDidLoad, and have tried declaring a custom var outside and inside ViewDidLoad (as well as not using one, but that seems incorrect). In ViewDidLoad, I have tried using tableView's .refreshControl, as well as .addSubview. In the selector func, I have tried placing .reloadData above and below .endRefreshing. Every variation produces one of the above two incorrect behaviors.
I am new to all of this, and completely frustrated, as all I'm trying to do is learn how to implement the feature on an iPhone. I saw a post stating UIRefreshControl does not work as of earlier this month, but I find it hard to believe that Apple would just leave this rudimentary and ubiquitous feature broken for weeks+. Can anyone please help? Thanks, and happy holidays!
I have a UIView in which I display a movie if a particular chapter demands it. This view is resized via constraints in Main.storyboard to adapt to iPhone. All works fine on iPad. It also works fine on iPhone unless the app is asked to reload when a movie containing chapter was last active meaning that a movie will be first-up on loading. In this scenario, the movie is loaded into the iPad dimensions instead of the smaller iPhone specs.
It appears that the constraints on the movie's view are not engaged in a timely manner. The issue centers on a query of the the view's bounds. If I insert a delay before using the bounds the issue goes away. In fact, a delay of 0.0 seconds does the job!
Using a kludge that relies on a delay seems pretty funky to me. I can also move the call that uses the bounds to viewDidLoad to resolve the issue but then I see some underlying “garbage” when reloading the app, the launch image seemingly not in effect. Any suggestions?
It sounds like you're using bounds before your views have been lain out. Without actually seeing your code, I would suggest executing your described code inside of viewDidLayoutSubViews().
I have a very intriguing obstacle to overcome. I am trying to display the live contents of a UIView in another, separate UIView.
What I am trying to accomplish is very similar to Mission Control in Mac OS X. In Mission Control, there are large views in the center, displaying the desktop or an application. Above that, there are small views that can be reorganized. These small views display a live preview of their corresponding app. The preview is instant, and the framerate is exact. Ultimately, I am trying to recreate this effect, as cheaply as possible.
I have tried many possible solutions, and the one shown here is as close as I have gotten. It works, however the - (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx method isn't called on every change. My solution was to call [cloneView setNeedsDisplay] using a CADisplayLink, so it is called on every screen refresh. It is very near my goal, but the framerate is extremely low. I think that [CALayer renderInContext:] is much too slow.
If it is possible to have two CALayers render the same source, that would be golden. However, I am not sure how to approach this. Luckily, this is simply a concept app and isn't destined for the App Store, so I can make use of the private APIs. I have looked into IOSurface and Quartz contexts, but I haven't been able to solve this puzzle so far. Any input would be greatly appreciated!
iOS and OSX are actually mostly the same underneath at the lowest level. (However, when you get higher up the stack iOS is actually largely more advanced than OSX as it is newer and had a fresh start)
However, in this case they both use the same thing (I believe). You'll notice something about Mission Control. It isolates "windows" rather than views. On iOS each UIWindow has a ".contentID" property and CALayerHost can use to make the render server share the render context between the 2 of them (2 layers that is).
So my advice is to make your views separate UIWindows and get native mirroring for free-(ish). (In my experience the CALayerHost takes over the target layers place with the render server and so if both the CALayerHost and the window are visible the window won't be anymore, only the layer host will be (which the way they are used on OSX and iOS isn't a problem).)
So if you are after true mirroring, 2 copies of it, you'll need to resort to the sort of thing you were thinking about.
1 Option for this is to create a UIView subclass that uses
https://github.com/yyfrankyy/iOS5.1-Framework-Headers/blob/master/UIKit.framework/UIView-Rendering.h#L12
this UIView private method to get an IOSurface for a target view and then using a CADisplayLink once per second get and draw the surface.
Another option which may work (I'm not sure as I don't know your setup or desired effect) is possibly just to use a CAReplicatorLayer which displays a mirror of a CALayer using the same backing store (very fast and efficient + public stable API).
Sorry I couldn't give you a fixed, "this is the answer reply", but hopefully I've given you enough ideas and possibilities to get started.
I've also included some links to things you might find useful to read.
What's the magic behind CAReplicatorLayer?
http://aptogo.co.uk/2011/08/no-fuss-reflections/
http://iphonedevwiki.net/index.php/SBAppContextHostManager
http://iphonedevwiki.net/index.php/SBAppContextHostView
http://iphonedevwiki.net/index.php/CALayerHost
http://iky1e.tumblr.com/post/33109276151/recreating-remote-views-ios5
http://iky1e.tumblr.com/post/14886675036/current-projects-understanding-ios-app-rendering
I have a NavigationController that stacks UIViewcontrollers that have UITableView among other UI elmeents. The tables I use are actually custom tables that use custom cell views. With this arrangement those tables don't show scrollbars of any kind even though I have configured in IB the Shows Vertical Scrollers to show them.
I've tried several ways of debugging this without success. If I print to console the value of this property (showsVerticalScrollers), it prints 1, so the property is properly set, and no, my table is not wider than its parent view, actually it's way more narrow than its parent view.
Are there reasons why a table won't show it's scrolls?... btw, this happens in iOS5 running in simulator. I'm using xcode 4.2 with SLeopard. I don't have access to an iPad to test it in the hardware but other tables I have in the same project, show their scroll bars without a problem.
EDIT
thanks for the answer... I did one last test and found that one of the causes for not showing a scrollbar is the number of elements shown in the table, when they fit in it without the need to actually scroll. Say if you have a table with 1 row and the vertical size of the table is too big for just one row?, then iOS won't show the scrollbar when bouncing.
It's hard to provide a possible solution without seeing any code, but the advice I can offer is to update your code to the bare minimum needed code to implement a UITableView and see if scrolling works, if it does, add in functionality in small increments, testing the scrolling with each new code addition till you reach the point that scrolling breaks. Incremental testing in this fashion helps to avoid issues like this where you are unable to effectively debug your application.
I'm taking a look at this widget, and it appears to be a UIPickerView, however I haven't seen anything provided by the iPhone SDK API that allows for horizontal scrolling only. Mostly it's all done vertically. Also there appears to be a custom graphic around this picker, so it might not be that either.
I'm curious if anyone is able to determine if this is indeed a UIPickerView or perhaps a hacked up UIScrollView? The widget is handy -- and I like its use. I found it in some random groceries app in the app store.
Here is the screenshot:
Thanks all.
I'd definitely use iCarousel library:
https://github.com/nicklockwood/iCarousel
The library is really well documented, the code is clean and maintained.
That is totally custom. You could indeed do something of the sort overlaying an UIImageView and an UIScrollView. I'd guess it's a 100% custom. As with all programming, there are many ways to do any single thing.
As I recently posted in response to this question, a class for an iOS horizontal picker control (STHorizontalPicker) has just been posted on GitHub. It's nowhere near as sophisticated as UIPickerView, but it provides the basic functionality for picking numeric values and the underlying foundation is probably a good starting point for adding more sophisticated functionality (it's a UIScrollView containing a UIView with multiple CATextLayers for the markers).
It was designed to be used in UITableCellViews and currently looks like this:
This website has source code for a picker that is aligned horizontally without subclassing it.
That definitely looks like a custom component. I'd suggest getting the .app file off your iPhone, opening up the bundle, and looking to see if there's a xib file for that interface. You may get lucky and find the component sitting in there. My guess is that it's a subclass of UIScrollView, but of course there's no way I could be sure of that without personally knowing the developer or the codebase.
You will recognize pickers by their giant screen-gobbling footprint :-) This is most likely a horizontal UIScrollView with a series of fixed-width labels (or images). The tricky bit is to have the bezel on top with a transparent center pass touches back to the underlying scroll view. Or you can take the easy way out and overlay four image strips (for each edge) and leave the middle open so touch events go directly to the scroller.
It's a custom control, but it's really not that hard to build.