I'm having difficulty adding some constraints automatically. Usually when I add a constraint in Storyboard I click on the item and add a constraint to it (be that align to center x or leading edges etc)
However, when I add a constraint programmatically I'm unsure how to achieve the same results. With the following code I'm hoping to make my _spinner view to be half the width and half the height of it's parent _loadingView.
[_loadingView addConstraint:[NSLayoutConstraint constraintWithItem:_spinner
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:_loadingView
attribute:NSLayoutAttributeWidth
multiplier:0.5
constant:0]];
[_loadingView addConstraint:[NSLayoutConstraint constraintWithItem:_spinner
attribute:NSLayoutAttributeHeight
relatedBy:NSLayoutRelationEqual
toItem:_loadingView
attribute:NSLayoutAttributeHeight
multiplier:0.5
constant:0]];
However running this produces some conflicts. The _loadingView has constraints stating that it should be 80% width and height of it's parentview which is the ViewController.view So _loadingView should be 80% of ViewController.view and then _spinner should be 50% of _loadingView. But by adding the constraints on the spinnerview it is causing a conflict.
So I thought it needs an x and a y coordinate so I specified the spinner to be placed in the center of the _loadingView as follows:
[_loadingView addConstraint:[NSLayoutConstraint constraintWithItem:_spinner
attribute:NSLayoutAttributeCenterY
relatedBy:NSLayoutRelationEqual
toItem:_loadingView
attribute:NSLayoutAttributeCenterY
multiplier:1
constant:0]];
[_loadingView addConstraint:[NSLayoutConstraint constraintWithItem:_spinner
attribute:NSLayoutAttributeCenterX
relatedBy:NSLayoutRelationEqual
toItem:_loadingView
attribute:NSLayoutAttributeCenterX
multiplier:1
constant:0]];
But this still produces conflicts and the spinner constraints are not being added.
Related
I added a FBAdView to a UIView in the view controller.
(I set the view background to red)
the FBAdView was created with adSize of kFBAdSizeHeight50Banner.
The problem is that the FBAdView calculates its width when it is being added, but after rotating the device it doesn't calculate its width again
I tried using autolayout but it didn't work
code for adding the FBAdview (Adding to UILabel with red backgroud)
FBAdView *fbAdView = [[FBAdView alloc] initWithPlacementID:#"***************_***************"
adSize:kFBAdSizeHeight50Banner
rootViewController:self];
fbAdView.delegate = self;
[fbAdView loadAd];
[self.banner addSubview:fbAdView];
code for autolayout - doesn't work
// Width constraint, parent view width
[self.banner addConstraint:[NSLayoutConstraint constraintWithItem:fbAdView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self.banner
attribute:NSLayoutAttributeWidth
multiplier:1
constant:0]];
// Height constraint, parent view height
[self.banner addConstraint:[NSLayoutConstraint constraintWithItem:fbAdView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:self.banner
attribute:NSLayoutAttributeHeight
multiplier:1
constant:0]];
// Center horizontally
[self.banner addConstraint:[NSLayoutConstraint constraintWithItem:fbAdView
attribute:NSLayoutAttributeCenterX
relatedBy:NSLayoutRelationEqual
toItem:self.banner
attribute:NSLayoutAttributeCenterX
multiplier:1.0
constant:0.0]];
// Center vertically
[self.banner addConstraint:[NSLayoutConstraint constraintWithItem:fbAdView
attribute:NSLayoutAttributeCenterY
relatedBy:NSLayoutRelationEqual
toItem:self.banner
attribute:NSLayoutAttributeCenterY
multiplier:1.0
constant:0.0]];
print screen
when the banner is added it fit the screen width
after rotating it doesn't change its width (like its parent red view)
I think you're missing some constraints.
Adding these lines (might need some minor changes) makes your code work:
self.banner.translatesAutoresizingMaskIntoConstraints = NO;
fbAdView.translatesAutoresizingMaskIntoConstraints = NO;
// Width constraint
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:self.banner
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeWidth
multiplier:1
constant:0]];
// Height constraint
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:[banner(==50)]"
options:0
metrics:nil
views:NSDictionaryOfVariableBindings(banner)]];
I've posted a sample project at https://github.com/overlordnyaldee/BannerAutoLayout
I have a UICollectionView added to a UIView. I just want the collection view to resize with orientation change, so that it fits the superview (UIView). After I add the layout constraint the collection view is missing. I could not even get the first constraint work properly.(below)
NSLayoutConstraint *leftSideConstraint = [NSLayoutConstraint constraintWithItem:self.collectionView
attribute:NSLayoutAttributeLeading
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeLeading
multiplier:1.0
constant:10.0];
And then I add the constraint to self.view.
What am I doing wrong? Please, help!
Update:
This is how it works. I am new to autolayouts. I was just trying to satisfy the constraints one by one to be sure that they all work:) Thank you
NSLayoutConstraint *constraint1 = [NSLayoutConstraint constraintWithItem:self.collectionView
attribute:NSLayoutAttributeLeading
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeLeading
multiplier:1.0
constant:5.0];
NSLayoutConstraint *constraint2 = [NSLayoutConstraint constraintWithItem:self.collectionView
attribute:NSLayoutAttributeTrailing
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeTrailing
multiplier:1.0
constant:-5.0];
NSLayoutConstraint *constraint3 = [NSLayoutConstraint constraintWithItem:self.collectionView
attribute:NSLayoutAttributeBottom
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeBottom
multiplier:1.0
constant:-5.0];
NSLayoutConstraint *constraint4 = [NSLayoutConstraint constraintWithItem:self.collectionView
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeTop
multiplier:1.0
constant:5.0];
[self.view addConstraints:#[constraint1, constraint2, constraint3, constraint4]];
You can't just add one constraint for view to position correctly. It needs to know it's x and y position, width and height. With this one constraint you only gave it x position. You need three more constraints eg. trailing, top and bottom or top, width, height. Basically any set of constraints that will fully describe view position, width and height.
To save performance I'm creating the date picker only once in my app via a Singleton class and want to add the date picker then programmatically. This works, however I don't really know how to set the constraints in order to center the Date picker within its cell. This is my code:
//Inserting and aligning the date picker
self.datePicker = [[Singletons sharedManager] datePicker];
[self.datePickerCell addSubview:self.datePicker];
// Width constraint, half of parent view width
[self.datePickerCell addConstraint:[NSLayoutConstraint constraintWithItem:self.datePicker
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:self.datePickerCell
attribute:NSLayoutAttributeWidth
multiplier:0.5
constant:0]];
// Height constraint, half of parent view height
[self.datePickerCell addConstraint:[NSLayoutConstraint constraintWithItem:self.datePicker
attribute:NSLayoutAttributeHeight
relatedBy:NSLayoutRelationEqual
toItem:self.datePickerCell
attribute:NSLayoutAttributeHeight
multiplier:0.5
constant:0]];
// Center horizontally
[self.datePickerCell addConstraint:[NSLayoutConstraint constraintWithItem:self.datePicker
attribute:NSLayoutAttributeCenterX
relatedBy:NSLayoutRelationEqual
toItem:self.datePickerCell
attribute:NSLayoutAttributeCenterX
multiplier:1.0
constant:0.0]];
// Center vertically
[self.datePickerCell addConstraint:[NSLayoutConstraint constraintWithItem:self.datePicker
attribute:NSLayoutAttributeCenterY
relatedBy:NSLayoutRelationEqual
toItem:self.datePickerCell
attribute:NSLayoutAttributeCenterY
multiplier:1.0
constant:0.0]];
I have a view(self.printSettingsView) created from xib. I add this view as a subview to another view(self.view). I programmatically add constraints as follows:
[self.printSettingView setTranslatesAutoresizingMaskIntoConstraints: NO];
NSLayoutConstraint *leftConstraint = [NSLayoutConstraint constraintWithItem:self.printSettingView
attribute:NSLayoutAttributeLeading
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeLeading
multiplier:1.0
constant:0];
[self.view addConstraint:leftConstraint];
NSLayoutConstraint *topConstraint = [NSLayoutConstraint constraintWithItem:self.printSettingView
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:self.topBar
attribute:NSLayoutAttributeBottom
multiplier:1.0
constant:0];
[self.view addConstraint:topConstraint];
NSLayoutConstraint *heightConstraint = [NSLayoutConstraint constraintWithItem:self.printSettingView
attribute:NSLayoutAttributeHeight
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeHeight
multiplier:1.0
constant:0];
[self.view addConstraint:heightConstraint];
NSLayoutConstraint *widthConstraint = [NSLayoutConstraint constraintWithItem:self.printSettingView
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeWidth
multiplier:1.0
constant:0];
[self.view addConstraint:widthConstraint];
All the other constraints take effect except for height.
What could i be doing wrong here???
Thanks
Without knowing the constraints on your xib file or what you expect to happen vs what is happening (a screenshot would be helpful) it's hard to say. However I do have one suggestion where maybe the logic isn't correct.
The second constraint is pinning printViewSettings top to the bottom of the topBar, that part makes sense. The next one however sets the height of printViewSettings to the height of its superview. This may not jive with what you want because your superview contains your topBar as well and so may be larger than you expect. What you might actually want is a constraint that pins the bottom of printViewSettings to the bottom of the superview instead.
Sorry guys about the incomplete information. The problem in a gist was that i was assigning a constraint to the subview in my main view and whatever be the constant of the constraint the size of the subview remained constant. I found that the issue was the subview in turn had components(subviews) with fixed height constraints. I made them proportional to the height of the parent view and it works now.
In my app, I have the following setup:
TextView (self.textView)
Toolbar
When the keyboard become visible, I add a constraint that pushes the bottom of the text view up with the required number of pixels.
spacer =[NSLayoutConstraint
constraintWithItem:self.textView
attribute:NSLayoutAttributeBottom
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeBottom
multiplier:1.0
constant:-height];
[self.view addConstraint:spacer];
When the keyboard disappears, I remove the constraint.
THIS WORKS FINE. However...
I want to add an imageview that lies on top of the text view. This seems straightforward. But now the "dismiss keyboard" resize is broken.
Here's the code I use to create the imageview, and pin it to the textview bounds.
self.overlay = [[UIImageView alloc] init];
[self.overlay setTranslatesAutoresizingMaskIntoConstraints:NO];
[self.view addSubview:self.overlay];
[self.view addConstraint: [NSLayoutConstraint
constraintWithItem:self.overlay
attribute:NSLayoutAttributeBottom
relatedBy:NSLayoutRelationEqual
toItem:self.textView
attribute:NSLayoutAttributeBottom
multiplier:1.0
constant:0]];
[self.view addConstraint: [NSLayoutConstraint
constraintWithItem:self.overlay
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:self.textView
attribute:NSLayoutAttributeTop
multiplier:1.0
constant:0]];
[self.view addConstraint: [NSLayoutConstraint
constraintWithItem:self.overlay
attribute:NSLayoutAttributeLeft
relatedBy:NSLayoutRelationEqual
toItem:self.textView
attribute:NSLayoutAttributeLeft
multiplier:1.0
constant:0]];
[self.view addConstraint: [NSLayoutConstraint
constraintWithItem:self.overlay
attribute:NSLayoutAttributeRight
relatedBy:NSLayoutRelationEqual
toItem:self.textView
attribute:NSLayoutAttributeRight
multiplier:1.0
constant:0]];
[self.view layoutIfNeeded];
Here's how it should look:
Initial before keyboard showing
Keyboard showing
Keyboard removed. Layout should be back to initial state, but instead I get this
Solution: Set the content hugging priority for the tool bar to 1.000 to avoid that it gets all stretched out.