I an making an extremely simple scrollview and doing it entirely in Interface Builder and cannot get it working.
According to IB the height of my ScrollView is 568. I have set a user defined runtime attribute called contentSize and set it at 320x900. Yet it simply will not scroll.
Here's a screenshot of my view:
If it was working, the word label should be bouncing all around, am I correct? Nothing happens at all. This is done entirely in IB I haven't touched code yet for this.
You need to uncheck the AutoLayout property in IB
You can refer this.
Related
I have a weird output with autoLayout used for following scenario.
I have 4 sub pages to scroll. (subPage or scrollPage has been designed separately with autoLayout).
MainView has a scrollView component which loads the sub pages.
Everything is fine except the starting. After first load, the sub page components are not arranged properly. As soon as it receives a first tap/touch, automatically re-scrolls/re-arranges to proper places. which looks like a bug.
The loading creates problem. I have attached 2 images for reference for the above scenarios.
FirstOne at the first loading
Second one just after tapping on scroll area
Second one is the proper one. I need to show this instead of the first.
Need help to fix this.
Thanks,
Satyaranjan
One more thing to note,
[myScroll scrollRectToVisible:CGRectMake(320*pageNumber, 0, 320 , 240) animated:NO];
this is not working As I am using dynamic width for the subPage. Because it will vary for iPhon5 and iPhone6
First, you generally don't want to set the scrollView's contentSize when using autolayout -- if your sub views are laid out correctly, it will do that automatically.
Try this:
constrain all four of scrollView's edges to its parent
make sure translatesAutoresizingMaskIntoConstraints is NO for all views
Create a view called "contentView" and parent it to the scrollView.
pin all four of contentViews's edges to scrollView
parent your subviews to contentView and arrange them with autolayout
If for some reason you need to change the size of a subview programmaticly, you need to override its intrinsicContentSize method to return the correct size after the change. After the change, you might need to call the view's sizeToFit method from its parent view (not sure about that -- it may happen automatically).
In general, when using autolayout, you should almost never explicitly set the size of anything. If it can't be avoided, you should do it by creating height/width constraints and modifying them at runtime in the updateConstraints method.
EDIT:
I made an example project which demonstrates how to set up a scrollView and a couple other things.
Take a look!
https://github.com/annabd351/AutolayoutTemplate
Hello there fellow iOS programmers. While creating an app I've ran into a problem I can't seem to find an answer to. Let's lay it out:
I'm creating a UIViewController with a UIScrollView as it's only child. Inside this view I have a UIView, and inside of this there is a list of UIViews with UILabels inside them. As you all know you need to specify a contentSize for a UIScrollView.
The problem is that the list needs to be dynamic with it's content, and I therefore have no way to know the views heights beforehand. I'm adding all views with constraints where the height is set to ">=0".
When I later try to set the height of the UIScrollView I need to either get the height of the UIView that the list is inside, or get the origin.y and height of the last view in the list. This of course needs to be ready by the time the view is displayed to the user.
I've currently tried view.systemLayoutSizeFittingSize(UILayoutFittingCompressedSize), which returned 0; view.systemLayoutSizeFittingSize(UILayoutFittingExpandedSize), which returned 10000; and view.origin.y + view.frame.height, which also returns 0. It seems to me like the constraints haven't taken effect yet.
I've tried setting both constraints and UIScollView.contentSize from viewDidLoad(). I've also tried to set constraints in viewDidLoad and setting contentSize in viewWillAppear; this yielded the same results. Setting constraints in viewWillAppear and setting contentSize in viewDidLoad only caused a crash.
Bottom-line: When should I set up the UIScrollView.contentSize if I want to get view.height or similar methods to return a correct result, while at the same time be ready by the time the user sees the view?
Btw, I'm making this app in Swift, so answers in this language is preferred, but I'm able to translate from Objective-C to Swift; post in whatever suits you best.
Thank you! :)
You say:
As you all know you need to specify a contentSize for a UIScrollView.
No, as TN2154 says, the constraints between the scroll view and its subviews are "interpreted as the content size of the scroll view" (emphasis added). This is a boon, because you no longer have to mess around with contentSize if doing auto-layout. Just set the constraints for the scroll view's subviews and the content size takes care of itself. This leverages the labels' intrinsic size (and make sure that the label's numberOfLines to zero).
The only trick is that it sometimes cannot figure out the correct width of the labels (because the trailing constraint is to the scroll view's content size, it will sometimes make the scroll view a horizontally scrolling one). You can remedy this by either manually setting preferredMaxLayoutWidth or by setting a width constraint between the label and the scroll view's superview.
Personally, while I understand the inclination to add the UIView containers between the scroll view and the labels, I'd suggest losing them unless you need them for some other reason. IMHO, it simply complicates the constraints unnecessarily. It's hairy enough as it is. Obviously, if these containers bear other utility for you, then go ahead and keep them (and they'll work fine), but if you're doing this simply for the sake of the constraints, you might consider eliminating them.
I have a XIB file where I specify constraints at design time.
In addition to controls with constraints, I also have controls that have no constraints in the XIB that I want to position programmatically at run time.
I do this by repositioning views manually in didRotateFromInterfaceOrientation.
When I rotate the device, my code places the controls that are manually controlled but then later it appears that auto layout messes up the placement of manual controls that have no constraints on them in the Interface builder.
Question - When exactly does Auto layout run if I rotate the device.
Auto Layout runs at the end of the run loop after setNeedsLayout is called on a view, or immediately when setNeedsLayout is followed by layoutIfNeeded. Note that there are many methods that may call setNeedsLayout in their implementation, such as addSubview:, removeFromSuperview, etc.
A couple suggestions:
Instead of updating your constraints in didRotateFromInterfaceOrientation:, try doing so in updateViewConstraints.
You may also want to add placeholder constraints in Interface Builder to the views you will position programmatically. I think IB will automatically constrain views to their x/y position if a placeholder constraint is not set, but I'm not 100% sure on that.
The important thing to know is that the results of constraint calculations are applied in layoutSubviews. So if you want to set frames, you do so after calling super in layoutSubviews or in your view controller's viewDidLayoutSubviews.
Having said that, I've only experimented with this. I've not done it in production code and can't say that you won't run into issues.
I'm actually not clear on whether it's OK to set frames manually like this. The only relevant bit of information I've come across is the following from Apple's Auto Layout documentation:
You cannot set a constraint to cross the view hierarchy if the
hierarchy includes a view that sets the frames of subviews manually in
a custom implementation for the layoutSubviews method on UIView (or
the layout method on NSView).
Here, the phrase "view that sets the frames of subviews manually" implies to me that manually setting frames is OK. I'd be interested to know if anyone has a see a more explicit discussion on this.
you must not change the frame you must connect the constraint with iboulet and in the didRotateFromInterfaceOrientation you can change the constraint like this:
(void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation{
if (UIInterfaceOrientationIsLandscape(fromInterfaceOrientation)) {
self.constraintTop.constant = 50;
}else{
self.constraintTop.constant = 100;
}
}
I'm trying to adjust the size of a button to (it's intrinsic size + a little bit more) in order to draw a custom background. However, every time I access self.titleLabel within the button, the size and position resnaps to that of the storyboard. I don't have to do anything with the label to reproduce this, just retrieve it from the button.
I've put logging code all over my button and view controller in order to find where this is happening. It's not coming from a relaying-out of subviews or any other notification I see to get within the view controller. The line before accessing titleLabel, the position and size are correct. The line after, it has snapped back to the storyboard position. Commenting out the access prevents the size/position snapping. Can someone tell me where or why this is happening?
I have no constraints set (that I can tell), but am I fighting against auto-layout here? Should I be doing this a different way like composing controls or something?
Something similar (or the same?) has been asked before at UIButton modifying titlelabel seems to change its frame and UIButton titleLabel resizes on press?, but both were left unanswered or explained away with just "maybe a bug."
If the project has auto-layout enabled, then YES, you're fighting auto-layout. You have two choices, either subclass UIButton so that you can override the intrinsic size calculation, or modify the constraints so that the intrinsic size is not used in any constraint. If you do the latter, then you probably want to create an IBOutlet to the constraint for the width, so that you can adjust the constant property as needed.
This isn't a bug, it's a consequence of auto layout. When using auto layout, you shouldn't set any frames. Instead, you should change the size or position by modifying the constraints. What's happening, is that whenever the view needs to be redrawn, the frame reverts to the frame that's defined by the constraints.
I am not sure what is going on and how to handle this. I have a UIView in a cell and I set the constraints using IB and for some reason it stretches out to the end of the cell. How can I stop it from stretching.
And here is the result:
I am dynamically injecting a stepper control but as you can see the UIView stretches to the end of the cell. I tried pin width then it completely messes up everything and does not even display the UIView.
Here is the screenshot of constraints:
Okay, let me draw some distinctions here.
The trivial way to this is you always have the stepper in the cell (and no UIView). For those cells where we are not supposed to see the stepper, you set its hidden to YES; for those cells where we are supposed to see it, you set its hidden to NO. That is what I would do.
The programmer way to do this is you don't have any blue UIView in your cell at all. You add the stepper in code, and you also provide its constraints in code to position it. You said:
so I don't have to hardcode the coordinates
But adding constraints in code is not "hard coding" the coordinates. With constraints, you describe the position conceptually in terms of insets from the superview, and as the superview resizes, you are still correctly positioned. So there is no philosophical objection to adding the stepper and its constraints, and it is just laziness not to do that.
The lazy but wasteful way is to do what you are doing, i.e. add the blue UIView in the nib as a guide. Even if you do use the blue UIView as a guide, though, you should be able to get this right if your constraints are right. I just tried this and I was not able to reproduce the problem: my blue view appeared in my cells in the same place where it appears in Interface Builder.
The instant solution is don't use Autolayout in the nib from which a UITableViewCell is drawn — i.e. uncheck "Use autolayout" in the file inspector for this nib. You will thus use old-fashioned springs-and-struts (autoresizing) to position the subviews.