I have 3 image views that I have placed in the nib. They need to start at a different y value based on portrait or landscape. Additionally, they will move to the bottom of the screen based on a button click. At that point, I remove the top constraint and add a bottom constraint.
Due to the complexity of this, I decided to handle those particular constraints in the code. However, I still get a warning that the y position for those image views is ambiguous.
Is there any way for me to tell Xcode not to worry, that I have set the constraints in code? The only solution I can think of is to create a constraint in the nib and delete it on view did load but that seems hacky.
You can add constraints that are removed at build time. This tells interface builder that you're going to handle it in code. Working on capturing a screen shot.
Related
My question is that, can I trust on
Resolve autolayout issues’ - “Add missing constraints”
option(as in the attached Screen shot), which automatically adds constraints to the objects present in the storyboard?
I used this and tried running the app in all screen formats and it works fine, so can I continue using this or is it wrong to consider “Add missing constraints” for the constraint design. I’m new to auto layout and any kind of response, explaining this concept will be appreciated. Thanks
Utilizing the automatic constraint system is a bad idea. Most of the time, it won't work dynamically for all screen sizes. It generally adds constraints so objects appear correct in the current resolution you're designing in.
For example, it may pin a label you have placed in the center of an iPhone screen based on the distance from the left edge of the screen instead of the X value. That distance from the edge is going to stay the same when you run it on an iPad and it's going to be significantly off-center to satisfy that constraint.
However, depending on the situation, it could pin them correctly (IE leading edges to the super view instead of a constant). You can use the automatic constraint system for suggestions to reference what you need to add still, but I would not rely on it for dynamic UI.
Spend your time learning autolayout instead of throwing darts in the dark, it's really not as intimidating as it seems!
No you should not trust. Add missing constraints will add constraints that are missing. It will not add constraints that's your design actually want.
So I suggest you to understand what constraint you'll require to complete UI.
`For every control, Compiler need to know its : x,y,width and height.
For example : You drag & drop UILabel on your xib. Now you add top space constraint. So compiler will give warning. Need constraint for : X position.
On above example width and height will take according to text of label. Now you had given top space so its y position is known.
But for X you didn't give any constraint. In this case if you use Add missing constraints. compiler will add constraint for x position according to your placement. It may be your require constraint or may be not.
No iT just add the required constant so may be they are fixed so remove all constraints and try again.
Just like what the others say, "Add Missing Contraints" will always give the result of the layout that you desired. It's best that you learn to add constraints manually. But, there are times that you can be lazy for a couple of seconds by using that method but only for very simple layout.
I'll just share my thoughts about when should we use this method.
I use "Add Missing Constraints" when:
My layout is very much simple, it's like I know that when I do it automatically will yield the same result as doing it manually. This help saves a lot of time.
I am setting up constraints manually, but sometimes I don't know what constraints I am missing because the object that I am setting the constraints still shows red lines(missing constraints). This is just my purpose of learning.
I'm working on my first swift app and I found out quickly that I need to use constraints to properly layout my page. So far I'm running into two issue.
The first one is that after adding some constraints, my view is pushed off the screen on the storyboard, but it looks fine(outside of my second issue) in the Assistant editor.
My second issue is that on some phone sizes the constraints are causing the text fields to expand when viewed in the Assistant editor and on an iPhone 6s test device.
I've added some screen shots below. Any help with this issue would be really appreciated.
Each time you add a constraint in storyboard, it is not automatically applied to your working view. You may think it should be applied immediately, but try to think think like this. If you have a view, and you apply height constraint (for example) and if Xcode applied it automatically you would get a view of width 0, since you haven't applied width constraint. That's why you need to tell Xcode to update constraints explicitly.
So when you want to update constraints, select view you want to update and go to Resolve Auto Layout issues, and click on Update Frames. This is located in the bottom right corner of your storyboard. It looks like a small triangle between two lines. Here you can update all views or just selected views.
For the second issue, you need to apply fixed width constraint to your stack view, instead of adding leading and trailing constraints. By doing that stack view will have the same width on each device.
I'm trying to figure out how to use autolayout, and there seems to be a lack of info about it on the internet. I placed a view within my view controller with three buttons inside it. Before I place any constraints, the buttons show up on the preview. However, as soon as I make ANY constraints, the whole sub view completely stops showing up in the preview. I made a constraint to center vertically, and then one to place it 25 pixels from the left edge. It should know exactly where to place it, but still nothing shows up.
Any ideas on why constraints cause my buttons to not show up?
With Autolayouts the constraints should be as clear as possible. You can try by adding size constraints as well as fix(right, top or bottom) constraints if necessary.
When you don't use auto-layout it positions everything manually. When you enable auto-layout it switches this behaviour off so you have an unconstrained object, which is why it dissappeared.
Turns out I didn't have constraints on the size of the sub view, so it didn't know how to center it. I didn't think I needed that because I thought it would default to what it's already at.
I have been learning Xcode and iOS and things are going well with coding but I am confused about a few options in interface builder.
It seems that when I add a contraint I can choose to "Update Frames" and then either "Items of new contraints" or "All Frames" but it seems that I don't always need to do this... sometimes I do and sometimes I don't - I don't think I truly understand the concept. It seems to be optional. When is the case to choose it or not?
Once a constraint is added, then should that be it?
There is also a context menu (Resolve autolayout issues) (3rd item on the bottom on interface builder, represented by a triangle between 2 vertical lines) which also allows me to Force Update of constraint or update of frame. Why is this needed ? I notice the options inside are usually disabled so I presume this becomes active when there are issues ?
I have tried searching the internet and I can't find anything specific; the more I read, the more confused I seem to get.
Also, a sanity check: a frame is the bounding box of every single control (view) not just the viewcontrol, so every view (control) as its own frame. Is this correct?
I'll try to explain the concept of constraints and storyboard representation.
Constraints - are used to determine the position of UIView elements inside your view. For example, the vertical distance from top of the view to UIView element top. When you add constraint using the storyboard it plays 2 roles:
Positioning the element inside a view when your app runs
Positioning the element in the storyboard representation itself
Update Frames - is used when you want to update storyboard display so that it fits the currently applied constraints. When the display of the storyboard does not match the constraints a warning will appear.
Add missing constraints / Update constraints - will create/change the constraints applied on UIView element to match what currently presented in the storyboard. Kind of the other way around from update frames.
This answer is not a replacement for Apple's Auto Layout Guide
You do not have to click on "update frame" every time you add a constraint, if you do, it will update the frame of the view to whatever it should be based on the constraints. Yes, every view has a frame and it is the rectangle relative to the views superview.
More often than not you'll probably click on update constraints (Shift + Command + =), this will allow you to resize views that are already constrained, and have the constraints updated to match.
This seems like it should be very simple, but I am having a terrible time trying to get every subview (they act like menu bars) constrained to the bottom of the parent view in the IOS storyboard.
There seems to be automatic constraints placed between the subviews that make them override the constraint I'm trying to set. I try to take these off, and then place the new constraints, but nothing seem to work as I loop over trying to reset constraints, over and over and over...
It should be very simple, set all of the uiviews to a particular width and length and set the distance between the bottom of the superview to be equal to 0. That's it.
The secret to happy constraint editing in interface builder is simple:
Don't do it
If that isn't possible, then:
Create your own constraints before trying to delete the system ones
Make judicious use of the pinning menu and editing constraints in the inspector
Don't drag and drop your views after you've added them - this causes interface builder to discard all constraints and set you up with a new set of "best guess" system constraints.
I've written more about this here but that's the gist of it.