Not understanding auto layout, constraints and size classes - ios

I'm a bit stuck and any help would be greatly appreciated!
I'll give you a quick overview. I have designs for a screen that were built in sketch using an iphone 6 screen size, then redesigned to fit and look right for an iphone 5/5s/5c, and 6 plus as those are the only devices that I want to support.
But the design portion or implementing the designs for just one specific screen size is easy and I understand that part. Where am I'm lost completely, is how to implement a design in one view controller that looks the way that it should in all the screen sizes I designed for.
I've gone through more than a few auto layout and size class tutorials and not sure how I properly use them so that the app recognizes "this is an iphone 5, use these image sizing and placements instead, and this is an iphone 6 plus, use these" and so on.
Everything I've seen to this point regarding auto layout and constraints only use 1 set of numbers to judge distance from elements for example, but all screen sizes would have different distances.
What am I missing or not understanding? I know I'm looking at something improperly.
Thanks in advance for all help!

You're correct that just one set of numbers could be used to judge distances, but this can still describe how a view should appear on different screen sizes. Your problem may be that you're thinking of constraints as describing the frame of your view? (Which obviously has to be different on every device). I find it more helpful to think of constraints as describing how each edge of my view relates to another view.
For example here's a view controller I setup with all the same constraints and how it would look on different devices. The constraints describe how the large grey view is pinned it's left and right edges 20 points from the left and right edges of its container view. It's pinned to 8 points from the top and 8 points from the top of the label. The label is centred vertically and horizontally and it has intrinsic content size. Each button is pinned 20 points from the bottom edge with button 1 and 2 being pinned to the 20 point from the left and right edges respectively.
I don't know if that helped or if that wasn't the answer you were after and you need to arrange your views differently depending on the device: you can tell Xcode which device size and orientation the constraints you're creating are for, using this button in Interface Builder.
Use it to select a device size/orientation. After, any constraints you create will only be used on that device. By default any width and height are selected so normally your constraints are applied to all devices.
Also, you cannot choose which devices you want to support, only the iOS version.

Related

XCode Auto Layout behaving badly

In order to get an iPhone layout to display at 'correct' dimensions on iPad, I'm putting everything (rose) into a view (blue) within the ViewController (gold)
Click / tap to see Schematic View
The iPad is shown as the larger frame with the grey status bar.
So to cater for 7plus size iPhones downwards, I'd have to set up constraints for the 7+ within an iPad frame with different priorities
in different directions. Once the blue view is set, i should happily be able to add my Sub Views in I.B.
Since the whole lot has to appear in the very centre of Ipads, step (1) is to set alignment centre-line constraints of the blue View with priority of 1000.
Next would be to fix the size for iPad displays larger then 7+. Acheived with setting size constraints as a maximum to shrink from. I've only shown the ≤680, so that height or less as in step (2) but a lesser priority, say 750.
Then for it to reduce down in size toward SE size i want to hold that say 20 points away from the viewController (gold). So the constraint for that should be ≥20. as shown at (3), I've assigned 740
The principal works nicely in the horizontal direction, but not the vertical. I've tried endlessly to adjust different priority assignments, including the 'Content Hugging' and 'Content Compression Resistance'properties and I never seem to get the desired results once I put the actual entities I want to see (rose) within the Blue view.
I've read Apple's Autolayout Design Guides closely enough to almost say I've written them, and after 35+years of CAD and 3D animation modelling, I think I could describe objects in text parameters before the iPhone existed.
But I've been bested here. Am I taking the long way 'round to just get an ** iPhone only ** layout to display correctly? My little bald spot thanks you for your answer.
If it were me, I'd use trait variations instead of trying to handle layout for every size class in one set of constraints. I think if you take that approach, you can accomplish what you're after with a lot less work and in a way that's independent of devices that may appear in the future.
Also, keep in mind that if your app supports iPad multitasking, you may have sizes on an iPad that you're not expecting (like iPhone portrait width in device landscape orientation).
With autolayout, try not to think in terms of device type or orientation. Think in terms of the appearance you want for a particular size class, wherever it appears, in whatever device orientation. That gives you the opportunity to create a the best user experience for a given display area, and will make your life easier during initial development as well as when new features are added or new user devices are in the mix.

Xcode : changing view size depending on screen size

I would like to change view size depending on the screen size of the device.
For example, the view should not have the same size on iphone 4s and iphone 6.
The best way would be to use size class, but iphone 4s and iphone 6 are in the same.
Is there a way to add custom size class in order to do that ?
Or should I set auto-layout constraint programmaticaly depending on screen size ?
Thanks
At this point in time you really only have one solution, and it is using constraints.
Constraints have been existing for a long time now and should be used in all iOS projects. Never EVER change view sizes using their frames. Always adjust the constraint instead.
You can achieve pretty much anything using constraints. There are many tutorials / stack posts about it, you'll be able to look it up.
From what I understand here, you want your view to be bigger on bigger screens, and smaller on smaller screens. Without any other information i can only show you a very trivial example.
Add 4 constraints in storyboard (or in code, but it's just easier in storyboard I believe) from your resizing view to another view. Those four constraints should be Top, Bottom, Leading and Trailing (Up, Down, Left and Right).
Each constraint will basically say "my view should be X units from its superview, on that side".
If you go in the constraints attributes you can configure different things, like "I want my left side to be X units from the right side of that other view".
I suggest you mess around with colored empty views and see how they work, and if you can, have a more experienced programmer answer your questions on the side, because constraints, as simple as they are, are quite confusing at first. It took me about 2 months to be what i consider comfortable with it, and I'm a full time developer.
I can answer a couple more questions here if you want, but I'm pretty sure we'll be off topic really fast !
Have fun using constraints, they're great !

Constraints for universal storyboard on iPhones

I'm struggling a bit with constraints on iOS with the differents screens sizes nowadays.
I tried google and stackoverflow to find a solution but my english does not seem fluent enough to find an answer.
I got 4 buttons verticaly aligned, the first and the last one are constrained by the edges of screens (kinda easy). But I'm really struggling with the constrains of the 2 middle buttons. I can't find a way to make them equally spaced from the left and right buttons on every size screens.
Is there something easy and tricky to make these constraints right ? Or am I doing it wrong and should I try to do it programmaticaly ?
Thanks
Add three invisible views in middle of each button, make their width equal with each other with constraint then your four buttons will be equally spaced. For the Y then you just need to pin it at your desired place.
If you are going to support only iOS 9 and higher, then use a UIStackView.
The solutions to this problem is very simple. This can be solved using the concept of "spacer views". You have to place invisible views between each red coloured view. You would be requiring 3 in your case. Then make their background as clear colour. .
Next, make their width equal and constrain their edges to the views that are after and before that view. You then define the size for red coloured view.
REMEMBER dont give the "clear coloured views" any fixed width. It would be determined by the runtime.This would solve the problem. Tell me if any more information is required.
Here is a blog post for the solution for this
http://adamdelong.com/fluid-layouts-with-auto-layout-size-classes-spacer-views-and-constraint-priorities/
This is the youtube video for this
https://www.youtube.com/watch?v=eSG-3-QpmWk&feature=youtu.be
Besides Tj3n's answer with views between buttons, you could use
A UIStackView (iOS 9!) where you use for settings Axis: horizontal, Distribution: equal spacing
A Toolbar (depends on what you want to do with your buttons) with toolbar items and flexible Space between them
Why not size classes? Apple introduced the concept of adaptive user interfaces in iOS 8 relying on a combination of Auto Layout and size classes.
If you aren't aware of what is size classes, there are plenty of tutorials available, please find one.
Summary: Apple very cleverly removed two story borads for iphone and ipad and made a single story board for universal app. No you dont have to struggle trying to apply autolayout constraint that satisfies all the screen sizes :)
Below are few of the size classes and their meaning :)
Regular width x Regular Height ----> iPad Potrait mode/ipad landscape mode
Compact width x Regular Height ----> iPhone 6 plus,iPhone 6,iPhone 5s,iPhone 5,iPhone 4s potrait mode
Compact width X Compact Height ----> iPhone 6,iPhone 5s,iPhone 5,iPhone 4s landscape mode
Regular width x Compact Height ----> iphone 6 plus landscape mode.
You can select the size classes you want to support from story board :) and start applying constraints specific to each size classes (like buttons in middle) or if you have generic one (like your buttons fixed to screen) for all the size classes.
You can deploy, remove, reuse or delete the constraints form various size classes.
SUMMARY: Buddy, If you are not using size class yet, its a high time to start using it :) There is a wonderful video on it in apple WWDC sessions 2014 i believe. Download, watch, start playing with it.
Happy coding :)
you can use equations to get this appearance.
use views' trailing points to get this.
View1.trailing = superview.trailing*(2.0f/9.0f)
View2.trailing = superview.trailing*(4.0f/9.0f)
View3.trailing = superview.trailing*(6.0f/9.0f)
View4.trailing = superview.trailing*(8.0f/9.0f)
if you make View1.width = superview.width*(1/9.0f) you can achieve what you want.
there are a lot of similar solutions for this issue. but the base is using trailing points.
It may also be done with using centerX positions of Views.
View1.centerX = superview.trailing*(3.0f/15.0f)
View2.centerX = superview.trailing*(6.0f/15.0f)
View3.centerX = superview.trailing*(9.0f/15.0f)
View4.centerX = superview.trailing*(12.0f/15.0f)
Thanks to LearneriOS answer, I solved my problem.
In order to get my wished result, I created 3 views with 10 width.
My first and my last button were already constrained. I constrained my first extra view to my first button with Horizontal spacing then i constrained my first extra view with the Center vertically in container. I then constrained my extra view to his own width and heights.
There come the important part: I did go on the constraint menus and selected the width constraint. The value inside was still 10 but I did change the priority from 1000 to 750.
Then I did copy my first extra view and constrained all of them to the nearest buttons, the same way I did with my first entra view but I removed their width constraint (to all the extra views but the first one) and constrained the extra views with the first one by plugging the: Equals Width.
Then I got my result, I hope it was clear enough and thanks again.

Size class does not works

I need to create an app with adaptive UI. for that I use auto layout and size class. but i can't get the expected result. it displays different UIs for different screen sizes. kindly guide me to create the adaptive UI(for all screen sizes). Thanks in advance.
This is indeed problem with constraints as mentioned in comments to your question. Using size classes only allows you to set constraints for all iphones at lowest level (that's why screen size for size class Compact x Regular is same for all iphones in xcode).
It is difficult to help you, without knowing all of your constraints. My advice is, use Preview assistant, where you can see all of your devices and generated UI. By opening this Preview assistant, tap on bottom "+" symbol and add device you wish to inspect.
As you can see on this screenshot, in my storyboard, there are margins around the middle view, however on iPhone 4, where width is smaller, these margins are lower (they have lower priority as constraint), while view retains it's width/height.

Should I lay out every element with auto-constraints?

Auto contraints seems like a bit of a chore. I have a bunch of elements in my main view (this is a single-view app) inside Main.storyboard. So imagine a few labels, buttons, controls, etc.
For example, take one label that says "Hello World" that's centered horizontally in the upper portion of the screen.
I need to add the following constraints to make it appear "normal" in my various devices ipad/iphone:
Horizontal Center constraint
Leading Space
Top Space
Trailing Space
It works, but it seems like a lot of work, I don't remember doing this work in the good old days (~3 years ago) with struts and springs. So I need to add all these constraints to each of my other elements too. So if I have 10 elements, I need roughly 10x4=40 contraints? Is this the ideal way to do this?
If it were up to me a view and the elements as I place them in the view and all controls in it would just be stretched relatively to fit the size of the device. An example would be like in photoshop, where we just decide what the overall image looks like and then scale the image to just fit the dimensions that we want. Is this possible in xcode?
Note that my app is just portait only - for iphone/ipad, but looks exactly the same in both (ie same layout for the controls)
You don't need to set that many constraints.
Horizontal center + top space would be enough given your example, or leading, trailing and top space.
If you are setting leading, trailing and horizontal center, you are over-specifying in that axis and possibly giving the auto-layout system contradictory information that will cause problems.
For that specific example: no, you only need a horizontal center and a top space, because UILabels have an intrinsic content size so their width and height is specified by their content and not constraints (unless you want them to be).
You didn't do this work in the good old days because Auto Layout wasn't on iOS then and there was only one particular possible iPhone size at the time: now there are 4. Auto Layout is an essential tool for modern iOS development.
As for controls stretching relatively to the device size, it depends on the control, but in general standard controls maintain the 44 point touch target rule - for example nav bars have gotten wider to accommodate wider phones but they haven't gotten any taller, because the larger screen size should be used to display more content instead of more chrome.
But yes, if you wanted to have controls have particular dimensions based on device size that is definitely possible with Auto Layout.

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