I have Imageview and UIView on View Controller. If Imageview is nil or image is not available then UIView replace its postion.Do any know how is it possible using auto layout?
For trying purpose, I have fixed height and width of both(Imageview and UIView). Imageview have "top 8 pixel" and "Horizontally in container" margin. UIView have "top 0 from Imageview" and "Horizontally in container" margin. Set Imageview to nil but it doesn't work.
A good suggestion would be to add both of the image view and the view in a stackView and follow the steps mentioned in: UIStackView Distribution Fill Equally.
However, you can achieve what are you asking for by adding additional constraint between the bottom view and the top layout guide:
and then, set its priority value to be less than the default (1000) -in my example I set it to 500- and the its constant value to 0:
Its appearance should be displayed as dotted line, meaning that there is another constraint -with a higher priority value- deciding the x axis of the view, if this constraint has been removed/deactivated the dotted one should be activated.
Finally, make sure that if there is no available image you have to remove image view from its super view (call imageView.removeFromSuperview()), setting it as hidden or setting its alpha to 0.0 doesn't activate the dotted constraint:
class ViewController: UIViewController {
//...
#IBOutlet weak var imageView: UIImageView!
// I'm checking in 'viewDidLoad' method just for describing purposes,
// of course, you can do the check when needed...
override func viewDidLoad() {
// if there is something wrong, you should call:
imageView.removeFromSuperview()
}
//...
}
The output would be:
Take the outlet of height constraint of UIImageView and do below code
if (imageview == nil){
imageViewHeightConstraint.constant = 0
}
else{
imageViewHeightConstraint.constant = 60
}
And other query you can ask.
You can manage this by giving priority to the constraints using auto layout. Give your UIView top space from ImageView and the TopLayout. Assign a lower priority to the constraint (any value less than 1000) where you have given top space from top layout guide. If your image is nil , remove the image view from the view using imageview.RemoveFromSuperView(), the UIView will automatically take the next constraint i.e. from TopLayout guide. I am attaching a screenshot where to find the priority of the constraint on storyBoard.
Related
TD;DR
It seems that in some cases systemLayoutSizeFitting does not return the correct height to correctly show / position all subviews of a view. Am I using systemLayoutSizeFitting wrong or is there some other way to avoid this?
Long story:
The XIB file of a UIViewController does not only contain the main view but also a number of other views which are added to the view controllers view at runtime. All these additional views should get the same height when they are added to the view controllers view.
The views might look like this: A simple container view holding some subviews which are stacked on top of each other.
Since the height of the container view should be flexible, the vertical spacing between the bottom button and the lable above it, uses a grater-than constraint.
To give all views the same height, I tried to measure the necessary height of each view using systemLayoutSizeFitting:
#IBOutlet var pageViews: [UIView]!
override func viewDidLoad() {
super.viewDidLoad()
var maxHeight: CGFloat = 0
for pageView in pageViews {
// Add pageView somewhere on view and give it leading, trailing and top
// constraint, but no height constraint yet.
addToView(pageView)
maxHeight = max(maxHeight, pageView.systemLayoutSizeFitting(CGSize(width: view.frame.width, height: UIView.layoutFittingCompressedSize.height), withHorizontalFittingPriority: .required, verticalFittingPriority: .fittingSizeLevel).height)
}
for pageView in pageViews {
// Give all pageViews the same height
pageView.heightAnchor.constraint(equalToConstant: maxHeight).isActive = true
}
}
This does not work, when the label text becomes to long:
In the right example the height is not large enough and thus the button is squeezed. I can counter act this by raising the vertical compression resistance of the button, however in this case the other controls (e.g. the title label) is squeezed...
Why is this? Why does not systemLayoutSizeFitting return a height which is sufficent to show all controls without any squeezing?
Its actually smash button's height when label text is getting bigger . You are setting top and bottom constraints but button height is not declared so when label getting bigger , view basically say "I can reduce button height before updating my height , I have space.Bottom and top constraints are still same , didn't effect."
Giving the constant height constraints of button might be fix your issue.
If you want your view to resist to compression you should use the defaultHigh priority as a verticalFittingPriority instead of fittingSizeLevel.
I'm trying to get a rounded UIImageView but it seems to render differently on different devices;
Looks like this on an iPhone Xr:
Looks like this on an iPhone 7:
I have a height constraint of 60 and the following code:
override func viewWillLayoutSubviews() {
super.viewWillLayoutSubviews()
self.userAvatar.layer.cornerRadius = self.userAvatar.frame.height / 2
self.userAvatar.layer.masksToBounds = false
self.userAvatar.clipsToBounds = true
self.userAvatar.layer.borderWidth = 0
}
Any ideas?
It seems to me that you have given the image leading and trailing constraints instead of a fixed width.
To achieve a circle give image view width equal to height.
This happens due to different widths of devices.
If you're managing this view using Interface Builder (i.e. Storyboard or XIB), you can enforce a square shape (which becomes a circle when combined with the rounded corners you already have) for the view directly from there by defining a constraint for its Aspect Ratio. No need to code anything.
Control-drag (like you do to create Outlets, Actions, etc.) from the image view to itself, and the following popup will appear.
Select Aspect Ratio, which will create a constraint matching whatever the view's current ratio is (in this example, it's 15:8). If the view was already square, the constraint created should already be correct.
If not, you can find that constraint by clicking the following icon (for the Size inspector):
From there, you can double-click on that constraint to edit it, and change the Multiplier to 1:1:
In fact, an even easier option is, once you've Control-dragged from the view to itself, hold down Alt/Opt and the option displayed in the popup will change to Aspect Ratio (1:1), meaning you can set it directly from there without even having to edit the constraint.
Constrain the height equal to the width.
And, create a simple UIImageView subclass:
class RoundedImageView: UIImageView {
override func layoutSubviews() {
super.layoutSubviews()
layer.cornerRadius = bounds.height / 2
}
}
The frame can (and will) change based on view lifecycle. By updating the cornerRadius in layoutSubviews() it will keep it "round".
I wanted the "number" & "status" to display on the left if there is not QRCode display (constraints has been set for image & labels.)
Result without QRCode:
.
The result with QRCode will be:
IT IS very easy just make width Constraint of QRcode image, if QR code is not available than make widht constant = 0,
#IBOutlet weak var width: NSLayoutConstraint!
if (your condition)
{
width.constant = 0
}
else
{
width.constant = 30
}
You can do that with a second pair of constraints attached to left side of a view.
Add outlets to that constraints and set constant value to desired offset(from code), if there is no QRCode View.
Another way is to add MoreThanOrEquel constraint to left side (e.g >= 10)
Than another constraint with constant value 10, but with lower priority.
When you remove QRCode view, it will destroy it constraints and constraints to left side will affects and move yours labels to left.
You could make constraint for labels that way:
I.e. make constraint for image leading to left side + image width, both labels also have leading to left side. Then if there is no QR Code adjust labels leading constraints to value you need.
Or you could make both labels leading to image view and set the image view width constraint to 0.
This Problem is very simple , can achieve using UIStackView just making hide/Show.
For Ex: If QR-code is present show or else hide QR-Code.
Label (Number and status and image) will automatically get adjust. Following is the screen short for better understanding.
IBOutlet UIView *qr_view; // Image or View
Case 1 :QR Present
qr_view.hidden = NO;// Show
Case 2: QR Not Present
qr_view.hidden = YES;// hide
I have a view that I am making hidden at the bottom of the screen, and want the scrollView above it to adjust and fill the void space.
The view at the bottom of the screen is a GADBannerView and has a fixed height of 50 (bannerHeight). The scroll view above it has a constraint to the bottom of the container that equals 50 (scrollConstraint). See photo.
In viewDidLoad is am setting these constraints to the following:
bannerHeight.constant = 0
scrollConstraint.constant = 0
This is causing the bannerView did disappear but the scroll view is staying in it's original position and not filling the void space.
You can force the superview to take into account the change of the constraint because this does not happen automatically. Add your code to viewDidLayoutSubviews() instead or simply call view.layoutIfNeeded() after you set the constants to 0 in the viewDidLoad().
If this does not work, you can try this alternative approach:
Go to your Storyboard and click on the scroll view's bottom constraint (the blue line that gives the scroll view its bottom constraint of 50). In the Attributes Inspector you should be able to see details about your constraint, it should look something like this
In the field that asks for an Identifier, give it the name "ScrollViewBottom" or whatever name you like.
Now loop over all the constraints that make up your scroll view and use the identifier name to find the correct one and change it's constant as follows
for constraint in yourScrollView.superview!.constraints {
if constraint.identifier == "ScrollViewBottom" {
constraint.constant = 0
}
}
Finally, force the view to take into account of this change by calling the following straight after
view.layoutIfNeeded()
Suppose I have three labels that are laid out below each other in a column. The uppermost label's top edge is pinned to the superview's top edge. All following labels' top edges are pinned to the preceding label's bottom edge. The leading and trailing edges of all labels are pinned to the leading and trailing edge of the superview. Here's what it looks like in Interface Builder (I added a blue background on every label to visualize its extent).
In the simulator the result looks like this.
All labels are connected to outlets in a view controller.
#IBOutlet weak var label1: UILabel!
#IBOutlet weak var label2: UILabel!
#IBOutlet weak var label3: UILabel!
When I set the text of label2 to nil
label2.text = nil
the label itself collapses.
However, the top and bottom spaces around the label do not collapse. This is evident by the fact that there is no blue background on the middle label in the last screenshot. As a result, the space between label1 and label3 is double the space of the layout in the first screenshot.
My question is - on iOS8 - what is the easiest way to collapse either the middle label's top or bottom space so that the two remaining labels still use the vertical spacing defined in the original layout? To be clear, this is the result I want to achieve.
Options I've found so far:
Bottom/Top Spacing Constraint Outlet
Define an outlet for the middle label's top or bottom spacing constraint.
#IBOutlet weak var spacingConstraint: NSLayoutConstraint!
Store the constraint's initial constant into a variable (e.g. in awakeFromNib or viewDidLoad).
private var initialSpacing: CGFloat!
override func viewDidLoad() {
initialSpacing = spacingConstraint.constant
...
Set the constraint's constant to zero whenever the text is set to nil or back to its initial value when the text is not nil.
spacingConstraint.constant = label2.text == nil ? 0 : initialSpacing
This approach feels a bit clumsy since it requires two additional variables.
Height Constraint Outlet
Set the vertical spacing around the middle label to zero and increase its height by the same amount. Define an outlet for the height constraint and proceed as above, setting the height to zero when the text is nil and back to it's initial value when the height is not nil.
This is still as clumsy as the previous approach. In addition, you have to hardcode the spacing and cannot use the built-in default spacings (blank fields in Interface builder).
UIStackView
This is not an option since UIStackView is only available on iOS 9 and above.
I'm using this UIView category for this purpose.
It extends UIView by adding two more property named fd_collapsed and fd_collapsibleConstraints using objective-c runtime framework. You simply drag constraints that you want to be disabled when fd_collapsed property set to YES. Behind the scene, it captures the initial value of these constraints, then set to zero whenever fd_collapsed is YES. Reset to initial values when fd_collapsed is NO.
There is also another property called fd_autocollapsed
Not every view needs to add a width or height constraint, views like UILabel, UIImageView have their Intrinsic content size when they have content in it. For these views, we provide a Auto collapse property, when its content is gone, selected constraints will collapse automatically.
This property automatically sets fd_collapsed property to YES whenever specified view has content to display.
It's really simple to use. It's kinda shame that there is no builtin solution like that.
Your solutions are good enough for me and I'd do Bottom/Top Spacing Constraint Outlet solution but since you want something different. You can use this third party: https://github.com/orta/ORStackView It has iOS7+ support and do exactly what you need.
This is low-key a pain all perfectionist devs learn about when trying to stack a bunch of labels. Solutions can get too verbose, annoying to folow, and really annoying to implement (ie. keeping a reference to the top constraint... gets annoying once you do it multiple times, or just change the order of the labels)
Hopefully my code below puts an end to this:
class MyLabel: UILabel {
var topPadding: CGFloat = 0
override func drawText(in rect: CGRect) {
var newRect = rect
newRect.origin.y += topPadding/2
super.drawText(in: newRect)
}
override var intrinsicContentSize: CGSize {
var newIntrisicSize = super.intrinsicContentSize
guard newIntrisicSize != .zero else {
return .zero
}
newIntrisicSize.height += topPadding
return newIntrisicSize
}
}
Usage:
let label = MyLabel()
label.topPadding = 10
// then use autolayout to stack your labels with 0 offset
Granted, its only for top padding, but that should be the only thing you need to layout your labels properly. It works great with or without autolayout. Also its a big plus not needing to do any extra mental gymnastics just to do something so simple. Enjoy!