I don't really understand constraints and have tried many different suggestions found online. All they seem to do is bunch everything up on top of one another or do nothing at all.
I have the following IPad application but I want it to work on any size device, mainly a IPod touch.
The page is simply two buttons that I want to remain the same no matter what screen they're on.
Any help on this appreciated.
It helps to think about points of reference that won't change with different screen sizes. Sometimes you want things on, say the top left corner so you just do constraints to the top and the left.
I'll give you two suggestions
Suggestion One
For your case, it seems like you might want to do constraints off centerY since you want them to be in the middle despite the screen size.
So I would make a constraint to "Center Vertically in Container" and then tap on the constraint and adjust it's value to negative or positive, so that way it's always X pixels above or below the centerY.
Now that's not going to be enough. it knows it's Y position but it doesn't know its height, width, or X position. So you need to add enough constraints to satisfy those.
A few examples:
X/Width: Two constraints to leading and trailing on each button OR Center horizontally and fixed width constraint. (again be careful with fixed width constraints since screen sizes can change, sometimes it's what you want though)
Height: Yeah just give it a height constraint in this case.
Note that this means no matter the screen size they'll always have the same gap between them (and maybe different gaps to the other edges).
Suggestion Two
Use a container view, either a stack view (fill, equal spacing, vertical alignment, a spacing value for gap between) or normal view.
You can make the view a fixed height based off the height and spacing between the buttons you want. Then simply center that container view horizontally and vertically on the super view.
Nonsuggestion
There are certainly other ways (like using buffer views with equal heights constraints. So you'd have an invisible view on top, a view in between and a view on bottom. and you'd give those equal heights constraints and align the buttons to the edges of the invisible views surrounding them. As long as you gave the buttons a fixed height this would work for vertical constraints) but I think these two would probably be the best.
Related
I would like to center four buttons horizontally and vertically. Each of the buttons shall get a background image later, so I think it's important that the aspect ratio stays more or less the same, otherwise the pictures won't fit onto the button.
A screenshot of what it should look like:
All buttons have the same size and should take up as much space as available (small margin, 10px or so, not more if possible). I don't know how to set the constraints that the application looks good on all devices (iPhone 5s and iPad 10.5").
The application must not necessarily run in all orientation modes.
How do I have to set the constraints?
This problem can easily be reduced to the problem of making a maximum square centered in its superview. You can do that easily with just four constraints:
The rest — the grid of buttons — just falls into your lap. For example, make my blue view a UIStackView containing a two UIStackViews, and there's your grid. Or you could do it with explicit constraints yourself.
If this app can rotate, you might need two sets of constraints, one for when the width is less than the height, the other for when the height is less than the width. You would then have to swap them in code. But that's another issue, and is not difficult.
Add them to UIStackView, for placing them horisontally use horisontal value for axis property you can customize it with distribution, alignment and other properties of UIStackView.
It's the easiest way
Suppose that I have the following view controller and this is how I want to see it on all iPhone:
If I run it on iPhone 6 it has the following look:
Here you can notice that UITableView not fit the whole screen and UIImageView doesn't placed at the bottom of the screen.
How can I achieve the required behavior via constraints in XCode 6? I thought that I need the following constraints:
Leading space and top space to container margin for UITableView
Bottom space and trailing space to container margin for UIImageView
Vertical Spacing between UITableView and UIImageView
But it doesn't work as expected even after auto-resolve constraints issues:
Thanks in advance.
Ok, a few things here:
Each view needs enough constraints to define it's x and y position, and it's width and height unambiguously. To start with, go back to Interface builder and delete all of your constraints and lay out the view as you would like it to look. You want to have control over every constraint added, don't let IB automatically resolve the issues, as in all likely hood it won't do what you want.
Do you have an image that is the size you want it to be on screen, once you've factored in #2x, #3x etc? If so, then your job will be easier, as the width and height of the image view can be defined by the width and height of the image (ie the image view's intrinsic content size).
In order to use Autolayout effectively, you need to think about your view holistically, and think about how you want your views to behave when the screen size changes, be clear in your head about the behaviour.
To achieve the layout you want, I would do the following:
Constrain the tableview's leading, top and trailing edges to the superview, with a constant value of 0. This means it can get wider and thinner with the device, it will stretch horizontally, but always stick to the top. This has defined the tableview's x and y position, as well as it's width (height still to go, but keep reading...)
Constrain the image view to match the horizontal centre of it's superview (x position defined) and constrain it's bottom edge to the superviews bottom edge (y position defined). If've you've got the right sized asset, then that will take care of the width and height too. If not, you could go ahead give it explicit width and height constraints.
Now we can constrain the tableview's bottom edge to the top of the image view, with a constant of 0 (ie touching). Note we haven't give the table view an explicit height constraint, so as the device screen grows vertically, the table view will stretch vertically.
Autolayout is hard at first. I'd recommended lots of reading to get over the initial hump, really get to know what a constraint is doing, it's limitations, and the way in which the system parses constraints to translate them into frames. This book is really good, and really helped me learn:
http://www.amazon.co.uk/Auto-Layout-Demystified-Mobile-Programming/dp/0321967194
Best of luck
First make sure you have selected the correct size class. The 'Compact Width | Regular Height' size class must be selected in the Interface Builder. Now add the Trailing space,Leading Space, Top space and Bottom space constraints to the table view. For the image view set the view mode to Aspect fit and add the constraints : Align Center Y ,Top space,Bottom space, Leading space, Trailing space and Aspect Ratio .
I have a relatively simple portrait-only UI, laid out in a Storyboard, with items which I want to vertically spread to fill both 3.5 inch and 4 inch screens.
In other words, I want the spacing between the controls to be adjusted so that the UI nicely fills the screen, irrespective of the screen form factor.
This doesn't seem like an unusual thing to want to do, however I just can't get Interface Builder (within Xcode 5) to add the right constraints - I only seem to be able to get it to add fixed vertical space constraints, which do not adjust for different screen sizes.
Does anyone know how to do this without resorting to programmatic UI construction? I've invested a lot of effort in getting the Storyboard-based UI just right.
The solution needs to work on both iOS 6 and 7. Thanks!
How to do this depends on exactly what kind of adjustment you want when the screen size changes. One way to do it to give the top and bottom most views vertical spacing constraints to the top and bottom of the superview, respectively. Add a view, I usually use a UILabel with no text, in between all the views you have stacked vertically, and give them equal heights to one another. Give one of those "spacer" views a fixed height, but edit it so its priority is less than 1000 (which means it's not mandatory that it be satisfied). Then add spacing constraints between each nearest neighbor above and below each "real" view and the "spacers", so that you have all the views from top to bottom connected together by vertical spacing constraints. When the screen size changes, the only thing that can change will be the height of the "spacers", since the priority is less than 1000, and all other constraints are mandatory. My constraints look like this:
The labels each have the standard (8 point) spacing to the "real" views above and below them. The top and bottom views should have whatever spacing you want to the screen edges.
Apple have now posted a document which describes the officially-endorsed approach to solving this problem:
https://developer.apple.com/library/ios/documentation/userexperience/Conceptual/AutolayoutPG/AutoLayoutbyExample/AutoLayoutbyExample.html#//apple_ref/doc/uid/TP40010853-CH5-SW8
Summary of the approach: insert spacer views between your controls, which have equal width/height (as applicable) constraints.
I have pretty straightforward requirements where two labels must be centered horizontally. So, I have selected them and chose Editor->align->center horizontally. Then added top space to container constraint to both of them. I also need the labels to shrink/grow regarding content size. However, IB shows errors and several warnings. I could make the labels shrink/grow just by adding pin between them (horizontal space) but they will not be centered in that case. Here are the screenshots:
here are the errors and warnings:
UPDATE theraven gave an interesting suggestion to use dummy view for centering it horizontally and pinning two labels to it. I have removed all existing constraints, added this dummy view and center X + center Y constraints to it. Then pined two labels to it (added horizontal space constraints). However, I still get a bunch of errors and warnings:
UPDATE2 Just updating the question, but still no valid answer found. #Theraven workaround works for iPhone4, iPhone4S, iPhone5 and iPhone5S, however it's not real centering but rather a workaround. Therefore for iPhone6 and iPhone6 Plus it doesn't work as leading and trailing spaces will be fixed and won't automatically resize for larger width.
What you could do is add both labels to another view, like a container view. Then you need to center this one horizontally and add the necessary constraints.
To add the containing UIView, you can select both labels, go to Editor -> Embed In -> View.
Then you would need to add constraints to make the containing view fit the two labels. So something like this:
First Label (left one):
Leading Space to Superview
Top and bottom Space to Superview
Horizontal spacing to the next Label
Second Label:
Trailing space to superview
Top and Bottom to superview (or align top with the first one)
Then the containing view should resize as to fit both labels. Then all you need to do is add the top offset constraint for this container view and a horizontal alignment it in the parent view.
This way, the containing view will grow as much as it needs to fit both labels and the space between them and will always be centered in the parent view.
I took a screenshot of my test constraints in case it helps you more.
Hope this was what you were looking for.
To solve this use a blank UIView in between your two labels and center it horizontally. Then pin the two labels either side of the centered blank view. It is common convention to use spacer views like this in auto-layout.
I really don't like the idea of adding another view just for sake of estethic.
Another alternative is to horizontally-center the left view, and horizzontally space the right view of an amout X with the left one.
Then to give the horizontally-align contraint of the first view a negative value equal to the first view width plus half the views distance. Or use multipliers as said in a previous comment.
But this only works with fixed width views i guess.
Use centered UIStackView as a container for two labels with a spacing required.
I didn't really understand what you wish to do.
The error you get (in the first screen shot) is that you are missing constraint for the x position of the labels.
For UILabel you must have constraint both for y and for x position regarding to the container view, when you selected them both and chose Editor->align->center horizontally, you just say that label1.center.x = label2.center.x.
You still need to say where they will be in the container view, you added the top space to container, so you do have the y position, but you didn't say where the x position should be.
You said
I have pretty straightforward requirements where two labels must be centered horizontally
But where they should be in respect to their container?
thanks
Using spacer views is the best possible solution I could figure out, even though it looks ugly for the developer. The user wouldn't even know what's going on behind the scenes and once you have the spacer UIView, you can always reuse it.
I have a UIViewController on my storyboard that has 2 subviews side-to-side horizontally. I added constraints to fix the leading and trailing edges to a constant (20 pts), and another constraint to keep the widths equal. If I assume the following, it should be possible to calculate what the width of each subview will need to be:
the subviews do not overlap
there are no other views present (horizontally, at least)
the width of the screen (the superview) is known
However, XCode gives me a warning that my views are horizontally ambiguous. I'm guessing that means that XCode is not making one of these assumptions, but which one is it? And is there a way for me to instruct XCode to make that assumption?
EDIT: Okay, played with it a bit and got the warning to go away, but it looks like it's not making the first assumption - it's just setting each subview's width to superview.width - 40, and happily burying one view underneath the other. So the question is how to I stop them from overlapping?
EDIT 2: Okay, my actual screen is a lot more complicated than my simple example. Here's what I got:
So in this setup I have 4 views that are vertically and horizontally staggered. I want the blue, red, and purple views to all be the same subview.frame.size.width = superview.width - 60. The blue and purple are lined up in the left column, and the red is alone in the right column, and all the gaps (between the two columns and between each column and it's nearest edge) are at a constant (20 pts). These 3 tables have a variable height, which I will be setting programmatically as described in James's answer here. At the bottom is a pink view that stretches the width of the screen (minus gaps), and sits at a constant 20 pts below either the purple or the red view, whichever is lower (which I'm attempting to do by giving it a spacing constraint of >= 20 to each view, and I hope that it will pick exactly 20 for one of them). Since all of the heights are dynamic and may not necessarily fit on the screen at the same time, I made their superview a UIScrollView instead of the normal UIView.
When all is said and done, I'm still getting a warning that all 4 of my views are horizontally ambiguous, and that the pink bar is vertically ambiguous. I think it's having trouble realizing what is supposed to go next to what, which is why it thinks it's horizontally ambiguous. And I think it's not picking to place the pink bar exactly 20 pts below either the purple or red views, which is why it thinks it's vertically ambiguous. Can anyone confirm or deny any of these suspicions? Or suggest a way around it? When I run it in the end, I just get this (I made the background of the scroll view yellow, which you can't tell in the storyboard screenshot):
Vertically Ambiguous
Okay, I think I've solved the vertical ambiguous part. I added two vertical constraints between the pink and purple views and two vertical constraints between the pink and red views. For each pair, the first constraint is that the spacing between them must be > 20 pts, and it has 1000 priority. The second constraint is that the spacing is = 20 pts, but it only has an 800 priority.
For example, if the bottom of the purple view ends up being lower than the bottom of the red view (as it is in my first screenshot), Xcode should try to set the vertical distance between the pink and red views = 20, but it will realize that that conflicts with condition that the space between the purple and pink being >= 20. Since the >= constraint has higher priority, the = constraint will be ignored. Now, when Xcode looks at the constraint that the spacing between the purple and pink views being = 20, it checks that against the constraint that the pink and red must be separated by at least 20. Since the bottom of the red view is higher than the bottom of the purple view, the >= 20 constraint between the red and the pink still passes.
So TL;DR, you can set up a view to have a spacing at a given value (x) from the most extreme of multiple views by giving it a >= x constraint with 1000 priority and giving it a = x constraint with <1000 priority for each view you are considering - and my vertical ambiguity problem has been solved. I do not yet have a solution for the horizontal ambiguity for all 4 of the views.
Horizontally Ambiguous
Okay, I got the horizontally ambiguous part fixed now as well. What it boils down to is that constraints in scroll views (and therefore table views) work differently than they do for any other kind of view. Here's what the step-by-step looks like.
Place the UIScrollView
Place a UIView into the UIScrollView to serve as a "contentView" for that scroll view
Add constraints to pin the contentView to all 4 corners of the scroll view AND pin it's width and height (so 6 constraints between the contentView and it's superview - 2 more than usual). Note that the width and the height can be pinned to something much larger than the normal screen size, which is probably why you are using a scroll view to begin with.
Add all of your other views you want in the UIScrollView (UIButtons, UILabels, etc. - I'm just going to assume UILabel from here on so I don't have to type as much, but any kind of UIView subclass will work) as subviews of the contentView, NOT directly as subviews of the UIScrollView
With this setup, the UILabels that are given constraints to their superview will constrain to the contentView, which has a defined size, so nothing is ambiguous.
Alternatively, if you want to fix the sizes of your UILabels (or dynamically calculate them, depending on the functionality of your app) and let the contentView expand to hold them:
Place the UIScrollView
Place a UIView into the UIScrollView to serve as a "contentView" for that scroll view
Add constraints to pin the contentView to all 4 corners of the scroll view AND pin it's width and height
create an outlet for the width constraints on the contentView (let's say we name it contentViewWidthConstraint)
place the UILabels
fix the sizes of the UILabels
create an outlet for the width constraints on the UILabels
Then in the code for viewWillLayoutSubviews
add up the widths of all of the UILabels and any gaps you want between them (as a CGFloat, which I'll call totalWidth)
set contentViewWidthConstraint.constant = totalWidth
And you're good to go! Note that I assumed you were setting the width in most of this example, but it should be just as applicable to height.
The problem is that many different widths of the two views will satisfy the constraints that you've set up. Here are two examples (I drew the shapes stacked vertically to make it easier to see the overlap example):
You can add a horizontal space constraint with a value of 0.