After reading about UIView's autoresizingMask on SO and developer.apple.com I'm still unclear what the purpose is. What's a situation where setting this property is necessary?
Yes, it is often necessary to set it if you don't want to resize the views manually. Note that it is mostly useful for subviews (i.e. those views that don't take the whole screen) rather then the main view of your app.
Views typically may need resizing if:
the device is rotated
an extra view (say, an ad) is added to the view, so the existing subviews have less available space.
For example, suppose if you have a view with two buttons on it, one in the top-left corner, another in the top-right corner. In order for the buttons to get wider when the view transitions from portrait to landscape, you need to set the FlexibleLeftMargin to the right button, FlexibleRightMargin to the left button.
Edit: autoresizingMask is also the first thing to look at if you see weird holes or overlaps when device is rotated or a new subview is added. Quite often the proper setting of these masks for subviews can get you a nice looking view in both orientations without having to lay out subviews manually - but usually it takes some experimenting.
Edit2: (since this is still gathering upvotes) Autoresizing masks are now mostly superseded with "Auto Layout", which allows for much more flexible constraints on views' sizes and positions. That being said, translatesAutoresizingMaskIntoConstraints is still occasionally useful for dynamically added views.
The purpose is that UIView properly shifts and resizes when its superview changes due to resizing, orientation change, showing editing controls in tableview cells etc.
Related
So I'm pretty new to AutoLayout, but more often than not I'm able to hack my views into shape or model off samples on the web.
However, I've created this rather complex view that just doesn't resize no matter what constraints I try.
Here are a few screenshots of what's going on.
The first shot is my Interface Builder layout. It's got a 4-corners kind of thing going on, with a UIImageView in each corner. In the center is a blurred VisualEffectView; it lays on top of the images. The layout was constructed with the parent view at 200x200
The second shot is a successful rendering at 200x200. As you can see, the 4 images load fine (yeah, I know they're a bit stretched, I just haven't handled their scaling code yet). Programmatically, I set the cornerRadius properties of both the parent view and the blurred view to 1/2 their width, so as to make them circular. Also programmatically, I added a label as a subview to the blurred view.
Then it all goes downhill. The third shot is my attempting to render the view at 250x250. The parent view renders well and maintains a circular shape, but just about everything else is wrong.
The most frustrating part is the UIImageViews, which all go haywire and extend their bounds even though I've set them to be equal widths.
The blurred view at least stays centered, but something isn't called which prevents its bounds.width property to be updated, which is what the cornerRadius is based off of.
The label doesn't stay center in the blurred view, despite setting its autoesizingMask to flexible all around.
Here is a snippet of my initialization code, which might be useful.
Any help that you all could provide would be greatly appreciated (even if it just fixes one of the several issues).
P.S. I apologize for the cats pics.
Edit: I achieved the desired result by writing the code manually and ditching Interface Builder and AutoLayout entirely.
I have a UIView, defined in a nib, and I need to be able to show/hide a middle button in that view. When I show the button, I need to reposition the two bottom buttons below it, as well as make the view taller to make room for everything. When I hide the middle button, I need to move the two bottom buttons up and vertically resize the view to make it less tall. I do NOT need to animate any of this since it the changes will never occur while the view is visible to the user.
I'm new to iOS and I'm used to using Autolayout, but I can't use Autolayout in this case to handle this automatically, so my current approach is to hardcode the frame position and dimensions for the two bottom buttons for each of the two different situations. I'm also hardcoding the two different frame sizes for the view itself. In viewDidLoad, I determine if I need to show/hide the middle button and set the frames for the view and bottom buttons appropriately. This works, but if feels hacky. Is there a better way I should be doing this?
Thanks in advance for your wisdom!
You don't need to hardcode your frame sizes in viewDidLoad. The only thing you should take care of is determining that whether you need to show you middle button or not. Within the implementation file where you are allocating your UIButtons, check if the middle button has to be shown, if Yes allocate it, if not then don't. The frames of two buttons and the view should contain a factor which can set/size them accordingly.
You'd basically be managing the Auto-layout programmatically. And if you're not even allowed to that then whatever else you'd end up doing would pretty much be a hack.
Within the pageViewController:viewControllerAfterViewController: method, just before the return statement, the view which is about to be returned as the next page has the correct view frame size.
However immediately after the pageViewController:didFinishAnimating:previousViewControllers:transitionCompleted: method is called, I check the frame size of the newly introduced view controller ([pageViewController2.viewControllers objectAtIndex:0];) and I find it resized.
Note that, I have set [self.pageViewController.view setAutoresizesSubviews:NO] and the autoresizing mask to None for the newly created ViewController.
Any ideas in which step the new ViewController is being resized?
I think the problem is inherently related to the nature of UIPageViewController. It is built from UIScrollView. I don't exactly know why there is strange resizing behavior, but it seems to be particularly pronounced when the view controllers that make up your pages use auto layout. Seemingly, locking the constraints in your page view controllers to the superview makes the elements resize after the transition because the superview is itself getting resized after said transition.
This sucks because Apple is basically pushing all of us to adopt auto layout. Auto layout is awesome, and I recommend everyone use it from now on, but it really really sucks when you use it with a UIPageViewController. They really ought to either scrap that class or build something easier for developers, something that can be dragged into a storyboard outright.
A few things to consider.
1.) Don't lock anything to the "Top Layout Guide" or the "Bottom Layout Guide". Also make sure you have "Constrain To Margins" disabled on any view intended to hug the sides of the screen.
2.) If you are using a label in your individual page / content view controllers, make sure you bind/constrain it to something other than the superview. I wanted to place a label over a UIImageView, so I aligned the label to the leading and top edges of the image view (using AutoLayout constraints only), creating an offset to give the label some margins.
3.) The following would otherwise be a good tutorial. However, it is a bit outdated. I downloaded the project and basically modified it to get a UIPageViewController implementation that works. The only problem with this project is that it doesn't use AutoLayout. I'm currently writing a blog post that more clearly discusses how to use UIPageViewController and Autolayout together.
http://www.appcoda.com/uipageviewcontroller-storyboard-tutorial/
Have a very large program where there is always a superview that just encompasses a custom segment controller. This view sits at the top of screen and controls navigation in several ways.
So the problem arose in only a selected few view controllers where everything was 100% programmaticly created. Essentially CGRect are not being defined in the property dynamic coordinates. But are not being recalculated on orientation change. Does anyone have a simple way to control this in the subview? I'm about to code something in the superview to pass to orientation to other subviews.. but there has to be a better way. Ideas?
Couple of pointers:
You can use auto-resizing masks to determine what happens to your views when their bounds change (ie, when the orientation changes). So UIViewAutoresizingFlexibleWidth means your view will 'stretch' proportionally with the superview when the bounds are changed. UIViewAutoresizingFlexibleLeftMargin means your view will effectively be right-aligned, as the left margin will adjust according to the width, etc etc.
Sometimes auto-resizing masks aren't enough - perhaps you have to change the view's content on an orientation, or do a complex animation. In this case, you use the willAnimateRotationToInterfaceOrientation method in your view controller. Your subviews might have a custom adjustForOrientation method that you've written that you can trigger when willAnimateRotation... is called.
Finally, on iOS 5 you can actually nest view controllers inside of view controllers, in which case orientation events get passed through automatically...but this is probably needlessly complex for what you're trying to do.
I am adding UIButtons to a UIView located on the right side of a split view controller. Without any autoresizing set, the button text fully displays in landscape orientation. When I rotate to portrait orientation, all button text is fully displayed, but there is extra space on the right hand side of the UIView, because there is more real estate to work with.
I would like these buttons to resize on rotation so that it utilizes the entire width. I tried setting:
[button setAutoresizingMask:UIViewAutoresizingFlexibleWidth];
With this in place, the same extra real estate exists on the portrait orientation, but in landscape orientation I get a lot of buttons with the text shortened with "..."
How can this be done?
when the AutoResisingMask doesnt do it for me, I always resort to subclassing the UIView and overriding the layoutSubviews... this way I can manually place those tricky views that never look right in different orientations.
in fact.. at last year's WWDC, I heard an Apple Engineer say that he "always" creates and adds his views with frame CGRectZero, then sets the correct frame in layoutSubviews. For what its worth...