ios placing 3 views inside another view with auto layout - ios

I'll briefly explain the situation: There is a ViewController VC and a View V inside it with the following layout constraints:
horizontal (left and right) spacing to VC is 0
vertical (bottom only) spacing to VC is 0
aspect ratio 75:23
like this:
____
| |
| |
|____|
|____| <- V
I wanna place place 3 view inside V, so lets say we divide V in 4 pieces:
___________
| | | | |
| | | | |
|__|__|__|__|
I wanna place my new 3 Views V1, V2 and V3 like this:
___________
| | | | |
| [1][2][3] |
|__|__|__|__|
that is, all centered vertically on V middle and the View Vi on (i/4) of V width.
How can I do this in storyboard (without code) ?

Connor's answer would definitely work, another thing you could do is use the NSLayoutConstraint Multipliers. Here are the steps:
1) Create three different UIViews all of equal width. For this example I used UIImageViews but that's irrelevant for this purpose.
2) Set each one to have the same vertical constraint (i.e. 50pts from the bottom, or set each one to be "Vertically Centered In Container"
3) To space them out evenly on the horizontal plane, you could set them each to be "Horizontally Centered In Container".
4) Once each view is horizontally centered in the container, change their multiplier to determine the distance the view's center point on the x-axis is from the superview's center point on the x-axis. If you wanted the three views to be spaced evenly, I would set the multipliers at (0.5, 1.0, 1.5) respectively.
Here's an image that show three views with a width and height of 50:
EDIT - To explain even further:
What's happening here is you're setting the center of the subview on the x-axis to align with center of the superview's x-axis, but when you set the multiplier you're telling it to be set a fraction of that distance. When it's set to 1.0 you're saying you want the subview's centerX to be 0.5 the width of the superview. When you set the multiplier to say 0.5, You're essentially saying you want the centerX of the subview to be 0.5 of 1/2 the width of the superview (1/2 * 1/2 = 1/4) so you're setting the centerX of the subview to 1/4 the width of the superview. Same thing with 1.5 - you're then saying you want the center of the subview to be 3/2 of 1/2 the width of the superview (3/2 * 1/2 = 3/4) so the subview's centerX would be 3/4 the width of the superview.

This is a great case for a UIStackView. Configure your container view (V) as:
let myContainer = UIStackView()
myContainer.axis = .horizontal
myContainer.alignment = .center
myContainer.distribution = .equalCentering
The axis tells it to stack subviews horizontally. The alignment gives the alignment for the non-axis; that is, it vertically centers each subview. And an equalCentering distribution will tell the stack view that the space between the centers of each subview should be equal.
Then all you need to do is configure the size of each subview (ie. add a programmatic constraint for width, dividing by the container width), and addArrangedSubview for each subview.

Related

Autolayout constraints for inscribed view [duplicate]

This question already has an answer here:
How to set the NSLayoutAnchor to generate an centered subview with aspect ratio 1:1
(1 answer)
Closed 4 years ago.
I have a view and it's subview. I want to define subview constraints to be the following:
Center X & Center Y of view and subview coincide (easy!),
Subview width & height are equal to
min(view.bounds.width, view.bounds.height)
How do I express this in terms of Autolayout constraints?
Here's one option:
Aspect Ratio of 1:1 with Priority: 1000
CenterX & CenterY with Priority: 1000
Top / Bottom / Leading / Trailing all set to >= 0 with Priority: 1000
Width = SuperviewWidth with Priority: 999
Height = SuperviewHeight with Priority: 999

I want to apply Auto Layout to UILabel like flexible height & width

I applied flexible height & width to my UILabel and now I want to use that type of functionality by using Auto Layout.
I am able to increase height and width of UILabel as Device width and height, but X and Y is not changed according to Device width and Height.
Ex:-
Device :- iPhone 7
UILabel :-
X : 20
Y : 120
Width : 300
Height : 30
Device :- iPhone SE
UILabel :-
X : 20
Y : 120
Width : 245
Height : 25
Now problem is that Size of UILabel decrease with aspect ratio but X & Y coordinate was not changed.
According to flexible height & width that will set like 17 & 102, but in auto layout it was not change.
Constraint :
Constraint Image
You have fixed X and Y Position for your label (Which is not device specific)
If you need to achieve this you need to set X and Y according to Centre of your view
I have create to set centre X (For Y Pos )
And How I have set centre of Y Pos
EXPLAINATION
The centre of UIView according to self.view is 318.5 and required space from top is 20 so final multiplier is 20:318.5
as every view has different centre
For Iphone SE centre would be around 17
Don't Forgot to set First Item to Label.Top as we need 20 from TOP
OUTPUT:
Hope it is clear to you :)
I have attach a image to make a label height dynamically. Select trailing constraint and change relation from "Equal" to "Greater Than Equal". Make sure number of line of label should should be "0".

iOS constraint equation values

I'm trying to find out what the values of the left and right views in a constraint equation are.
Currently this is how I see it.
The origin-point (0,0) in the coordinate system is at the top left.
Therefore views.attribute that are closer to the top and left are smaller.
In the image posted above.
RedView.Leading has a higher value than BlueView.trailing.
The equation is satisfied because 8 is added to BlueView.trailing.
The same would apply to the circled constraint in the image below.
superView.top is less than greyView.top because superView.top is on origin.x .
My question is are the values relative to the origin point ?
Theory of Relativity in Auto Layout
Short answer:
Yes and no. Actually more no. But most importantly: It's irrelevant!
Detailed answer:
Layout attributes are abstract descriptions of a view's position and size.
Position attributes:
top
bottom
leading
trailing
...
Size attributes:
width
height
While size attributes can describe an absolute value (e.g. view.height = 20.0) position attributes are always relative to another position attribute. That's why Apple only shows two views in their example, without any coordinate system. The equation
RedView.leading = 1.0 × BlueView.trailing + 8.0
states that RedView's leading edge is always 8.0 points to the right of BlueView's trailing edge. The origin of the underlying coordinate system doesn't matter!
Let's say we have a coordinate system ∑1 with an origin O1 and let's assume that BlueView's trailing edge is at x = 100 with respect to that origin. This would mean:
BlueView.trailing = 100
RedView.leading = 1.0 × 100 + 8.0 = 108
Now we look at a different coordinate system ∑2 with an origin O2 that's shifted by 20 points to the left, so
O2.x = O1.x – 20
O2.y = O1.y
In this coordinate system BlueView's trailing edge is at x = 120. So we get:
BlueView.trailing = 120
RedView.leading = 1.0 × 120 + 8.0 = 128
As you can see the values for the layout attributes BlueView.trailing and RedView.leading are different in ∑1 and ∑2. However, the horizontal spacing between the views is the same
RedView.leading – BlueView.trailing = 8
in both coordinate systems.
And that's the whole point of Auto Layout:
To describe the positions and sizes of views relative to each other, rather than using absolute values with respect to a particular coordinate system.
When I tell you to park your car behind your neighbor's car and leave a 1 meter gap in between, you know what to do, right? Without knowing where the road begins!
It's not important.
However – and I guess that's what made you ask the question – the system will need to "tell" the display at some point which pixels to draw for a particular view. And the pixel grid does have an absolute origin and a fixed coordinate system.
So eventually, the system will substitute the layout attributes for the outermost view (the window) before solving all the constraint equations. At that point in time your layout attributes will be relative to a particular origin (most likely the window's origin in the upper left corner, yes) but it's simply irrelevant!
Apple may choose any coordinate system they want (even a coordinate system whose origin is 50 points above the screen) and regardless of that particular system your layout will still look the same with the same set of constraints.
No, values are not relative to origin point. Forget about this.
To position them there must be some additional constraints applied to such attributes of views as:
left, right, top, bottom, leading, trailing, width, height, centerX, centerY, lastBaseline, firstBaseline, leftMargin, rightMargin, topMargin, bottomMargin, leadingMargin, trailingMargin, centerXWithinMargins, centerYWithinMargins.
Also in iOS 9 there were added diffrent kind of anchorPoints to make adding constraints easier.
Also Autolayout added localized leading and trailing attributes which position (leading is at left or right side of view) depends on Device Locale.
I would suggest the following equations:
redView.width = 0 + 1 * blueView.width
redView.height = 0 + 1 * blueView.height
redView.leading = 20 + superView.leading
blueView.trailing = -20 + superView.trailing
redView.bottom - blueView.bottom
redView.bottom = superview.bottom - 20
So it does not matter where origin is.
Everything you are asking requires knowledge of Auto Layout.
Leading, Trailing, Top, Bottom and other several constraints are applied w.r.t to the views.
Example:
RedView.leading = 1.0 x BlueView.trailing + 8.0
here, the leading constraint of RedView is applied w.r.t the BlueConstraint trailing whatever it is. i.e. RedView is placed 8 points farther than BlueView in horizontal direction.
https://developer.apple.com/library/content/documentation/UserExperience/Conceptual/AutolayoutPG/index.html
provides a good knowledge of the auto layout constraints, in what context they are applied and the how the views layout according to them.
Also there are top layout guide, bottom layout guide, margins with respect to which you apply constraints to a view.
Read more about auto layout to get a clear understanding.
Edit:
Example:
BlueView frame: (x: 0, y: 0, width: 4, height: 2)
Now the BlueView trailing that we have is: 4
So now we are setting RedView leading as:
RedView.leading = 1.0 x BlueView.trailing + 8.0
i.e. RedView.leading = 1.0 x 4 + 8.0 = 12.0
So now the frame of RedView is: (x: 12, y: 0, width: 4, height: 2)
Also from above equation,
BlueView.trailing = RedView.leading - 8.0
i.e., BlueView.trailing = 12.0 - 8.0 = 4.0
So, the equation is valid for both RedView and BlueView.

Xcode: I've set my UIImageView to both Min and Max width, then why is it always the smallest size?

I've put the following constraints to my UIImageView (Name = RunwayGallery):
Width: >= 200
Width: <= 600
Align Center X to: Superview
100:133 Ratio to: RunwayGallery
Top Space to: ImageAbove, Equals 10
So why is the UIImageView always 200 width? Even when there is enough screen space on both sides (and below) to enlarge the UIImageView to fill the screen.
Many thanks.
Don't define the width of the image view in constraints. Define the padding that you want to the left and the right of the image view. Then auto layout can make your image view as large as possible without growing too large.
You need to add more constraints to tell the UIImageView which width between 200 and 600 to choose.
What do you expect the width of the superview to be? Assuming the superview's width will be between 200 and 600, you can tell the UIImageView to fill the width of the superview by removing both width constraints and adding the following constraints:
Leading Space to: Superview Equals: 0
Trailing Space to: Superview Equals: 0
Now the UIImageView knows to stretch so that there is no space between its leading (left) and trailing (right) sides and the superview's leading and trailing sides.
Alright, I've mixed some of the answers of you guys and came up with this:
Leading Space to: Superview Equals: 0 (priority 900)
Trailing Space to: Superview Equals: 0 (priority 900)
width <= 600 (priority 1000)
This fully works. It makes sense if you think about it. It is filling to both sides with the leading and trailing space, UNLESS it becomes greater than 600.
Thanks for the answers! Appreciated.
EDIT: This is still the same:
Align Center X to: Superview
100:133 Ratio to: RunwayGallery
Top Space to: ImageAbove, Equals 10

change Auto Layout dynamically

I have to show 3 Labels like
LABEL1 | LABEL2 | Label3 //Horizontally
I want these 3labels width are equally divided according to Screen size width
How can I achieve this with nib file directly?
Thanks
Question 2
Label1 | Label2 | Lable3
//All Labels widths are equally
//All Labels are Subview of a view call X view
Label1 : height is 100
Label2 : height is 150
Label3 : height is 300
Q: Now I want X view's height as max(100,150,300) = 300
Just give top, left , right, height and equal width constraints to all label....

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