I have a UIViewController which I add to another UIViewController as a child. When the child gets added, the parent set frame on my child using childVC.frame = ...., but this fubars my constraints.
I can duplicate this issue in IB easily. Create a UIViewController, change the size to be "Freeform" and ditch the status bar (just so it looks right visually). Add in a UIButton (or anything) and constraints so so they are both the same size (see image below)
Now change the size of the top level view in the view controller and watch what happens.
It changed my constraints on me. I wanted my button to just get bigger and still hold the original constraints. Something which happens automatically if you toggle between iPhone retina 3.5/4.0 in screen or change from landscape to portrait. But why not when I resize the view? This is making a royal pain to lay things out in freeform and test different sizes.
More importantly... why does the exact same thing happen when I set the frame in code when I add the child for my VC and how do I prevent it?
Frame based calculations and Auto Layout are not compatible. Or at least, they mean stormy waters. That's why you are having issues. Having switched to Auto Layout you have to accept that you no longer manipulate frame directly.
So, you cannot do childVC.frame = whatever.
Instead, you must now use Auto Layout to update the size of childVC.frame. Do that by creating - in IB - an IBOutlet that is the width constraint of childVC. Similarly, create another IBOutlet that is the childVC height constraint.
In your view controller, update the constant value to change the size.
myWidthConstraint.constant = 123.f;
The place to do this is in the controller's updateViewConstraints method, or in the case of a view, updateConstraints.
That said, it's better to set up Auto Layout so that you don't need any programmatic updates. When properly defined, it will know how to handle things with the view's bounds change. To be honest, it should only be necessary to update sizes programmatically if you want to do something more unusual.
Can I just say however that you are better
Related
I have a subclass UITableViewCell. In storyboard I added some labels and buttons and created respective outlets, and I set and tweaked their respective frames using the size inspector. The layout looks good for a iPhone 6. On an iPhone 5 things are off screen on the right. In the layoutSubviews method of the UITableView subclass I attempt to adjust the frame of my labels and buttons. When the tableview first appears the buttons and labels are in the positions specified for their respective frames in Storyboard and not in the frame/position I set in layoutSubviews. A moment later they appear in the positions set in layoutSubviews. Sometimes however, I see it revert to the old storyboard set position.
Any ideas what might be happening? I want to set the labels and button frames explicitly and have them stay where I put them. I don't want to use constraints as they are really painful to use in Storyboard, and frequently don't behave well or with good granularity.
If you do not use constraints, please remove use auto lay out and use size class.
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
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 have a UITextView set in my storyboard at a certain position. When the app first loads up, I would like the textView to be at a different position then where it is in the storyboard. I do this programmatically by setting its frame to a different frame with a different origin (later the textView will be animated back to the original position). But no matter how I do it, the app always starts up with the textView in its storyboard assigned position. I can't seem to do this anywhere... viewDidLoad:, viewWillAppear:, nothing works. How can I override it?
One other thing... lets say the textView has a different origin then it does in its storyboard (the frame was reset at some point in the app). If I add a subview to the textview using addSubView:, the textView resets to its original position in the storyboard. Why?! Any way to stop this?
If you want to change the position of the textView when it starts up, I'd suggest that you do not have it in the storyboard and instead add it to the subview with its correct frame.
Especially with Autolayout in effect, having it there already means you would have to modify its constraints and if you're modifying its position programmatically already anyway, you might as well add it to the view programmatically too where you have more control over its constraints programmatically as well.
Under auto layout you can't set frames - well, you can, but as soon as another layout pass takes place, the frame will be reset to that defined by the constraints.
The simplest way to change the size or position of views you've laid out in interface builder using auto layout is to create outlets to the various constraints, and then edit their constant properties. If that doesn't give you enough flexibility, you still need outlets to the constraints, but when you want to move things you'll have to delete those constraints and add new ones.