I have 2 views that I have taken in storyboard but I haven't set any layouts in the storyboard.I want to set them by code.So here is what I did:
I read about autoResizingMask property of a view and 'translatesAutoResizingMaskIntoConstraints'.So setting 'translatesAutoResizingMaskIntoConstraints' to 'NO' makes sense.So I have done that but still I' not able to set the constraints programmatically.Now,as some constraints are automatically set in storyboard when we take the views from storyboard,I tried:
[self.view removeConstraints:[self.view constraints]];
After doing this,it removes all default constraints from the superview(i.e. self.view).But still I am not able to set constraints from code.What should I do?I need some guidance.
Here is my code that I have been using:
[self.view setTranslatesAutoresizingMaskIntoConstraints:NO];
NSLayoutConstraint *layouts1 = [NSLayoutConstraint constraintWithItem:_redView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:_yellowView attribute:NSLayoutAttributeWidth multiplier:3.0f constant:100.0f];
[self.view addConstraint:layouts1];
Related
Here is my problem, I have a scroll view scrollExerciseIndex that I use only as a scrolling bar, in this scroll view I place a UIView indexesView and I want it to be always at the center of the scroll view. For this I use layout constraints :
UIView * indexesView = [[UIView alloc] initWithFrame: CGRectMake(xPosition, 0, dimension*numberIndexes, dimension)];
[self.scrollExerciseIndex addSubview:indexesView];
[self.scrollExerciseIndex setContentSize:CGSizeMake(dimension*numberIndexes, dimension)];
if (xPosition != 0) {
NSLayoutConstraint * xCenterConstraint = [NSLayoutConstraint constraintWithItem:indexesView attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.scrollExerciseIndex attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0];
[self.scrollExerciseIndex addConstraint:xCenterConstraint];
}
Here is the expected result :
Don't pay attention to all the element, just the bar at the bottom of the screen is my problem.
I have to create view programmatically because sometimes I will activate the constraints, sometimes not and I have to set the frame of the view dynamically. So for now I initialise the view indexesView like so :
UIView * indexesView = [[UIView alloc] initWithFrame: CGRectMake(xPosition, 0, dimension*numberIndexes, dimension)];
(I know, not very original)
I would like to know if there is a way to initialize the view programmatically but to say to auto-layout that it has no constraints on the position because right now if the screen turns in landscape mode there is a conflict as the scrollview's frame changes so the distance between the center of the scroll view (on which I set a constraint) and the position of the subview's frame (xPosition) is no longer the same.
As you can see, the view is no longer at the center of the scroll view and I have some constraints broken.
Will attempt to recover by breaking constraint
NSLayoutConstraint:0x7bed6c50 UIView:0x7bed6ad0.centerX == UIScrollView:0x7e273200.centerX
Thanks for your help.
Ok, I found what I was looking for by reading a book about Audio-Layout.
My problem was that audio layout would create constraints behind my back automatically. When using AutoLayout a type of constraints is created from non-autoLayout specifications (The used to describe interface when auto layout didn't exist). So constraints are created using the initial frame of the view. The only thing I had to do was :
[indexesView setTranslatesAutoresizingMaskIntoConstraints:NO];
to disable this creation of constraints from the frame, and then recreate explicitly the constraints for width and height if needed (which wasn't the case for me, but I still made the test) like so :
`NSLayoutConstraint * widthConstraint = [NSLayoutConstraint constraintWithItem:indexesView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1.0 constant:widthValue];
NSLayoutConstraint * heightConstraint = [NSLayoutConstraint constraintWithItem:indexesView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1.0 constant:heightValue];
[indexesView addConstraint: heightConstraint];
[indexesView addConstraint: widthConstraint];`
When adding constraints programmatically, don't forget to call : [indexesView setNeedsUpdateConstraints]; so the constraints are recalculated only when needed.
Last info that I read and can be useful in general, when adding a lot of constraints, the apple doc specifies that it is more efficient to use the method :
[myView addConstraints:(NSArray<NSLayoutConstraints *> *)] than to call addConstraint: for each constraint.
Hope it can be useful to someone.
I have a view controller set up in a storyboard. The view controller's view contains a subview(UITableView) with pinned edges to the 4 sides of its parent, essentially making the view fill its parent.
I am adding the view controller's main view as a subview of another view controller's view like this:
UIView *overlayView = firstViewController.view;
[overlayView setTranslatesAutoresizingMaskIntoConstraints:NO];
UIView *sourceView = secondViewController.view;
[sourceView addSubview:overlayView];
NSLayoutConstraint *constraint;
constraint = [NSLayoutConstraint constraintWithItem:overlayView attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:sourceView attribute:NSLayoutAttributeLeading multiplier:1.0 constant:0];
[sourceView addConstraint:constraint];
constraint = [NSLayoutConstraint constraintWithItem:sourceView attribute:NSLayoutAttributeTrailing relatedBy:NSLayoutRelationEqual toItem:overlayView attribute:NSLayoutAttributeTrailing multiplier:1.0 constant:100];
[sourceView addConstraint:constraint];
constraint = [NSLayoutConstraint constraintWithItem:overlayView attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:sourceView attribute:NSLayoutAttributeTop multiplier:1.0 constant:0];
[sourceView addConstraint:constraint];
constraint = [NSLayoutConstraint constraintWithItem:overlayView attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:sourceView attribute:NSLayoutAttributeBottom multiplier:1.0 constant:0];
[sourceView addConstraint:constraint];
[sourceView layoutIfNeeded];
I want to have a gap from the right edge of the view to its parent equal to 100 pixels.
Now weirdly enough this works as expected on iOS 8, but fails to do so on iOS 7 and the view is displayed full-screen ignoring the 100 constant set on the trailing constraint. Also, if the view controller's view that is being added has no child views - then it is working as expected. Is setTranslatesAutoresizingMaskIntoConstraints: being applied to all the subviews of a view in iOS 7 ? What might be the reason for this ?
EDIT:
The issue lies somewhere in the way subviews are being managed by the OS.
When the Container View is set as a outlet to the view property of the view controller, things don't work. If however, I set the Table View as an outlet to the view property, the it works. Something weird happens if there is a child view with pinned edges to its superview and then I am adding other constraints to the superview. I dont understand why it works fine on iOS 8 though...
EDIT 2
The problem seems to happen only with the trailing constraint. If I want to modify the constants of any of the other constraints there are no issues ?!
Can you try interchanging sourceView with overlayView in your constraint?
`constraint = [NSLayoutConstraint constraintWithItem:sourceView attribute:NSLayoutAttributeTrailing relatedBy:NSLayoutRelationEqual toItem:overlayView attribute:NSLayoutAttributeTrailing multiplier:1.0 constant:100];`
This essentially means that sourceView.trailing - 100 = overlayView.trailing; which is not what you would want.
Edit 1:
Is setTranslatesAutoresizingMaskIntoConstraints: being applied to all the subviews of a view in iOS 7?
NO. translatesAutoresizingMaskIntoConstraints is set only for the views you explicitly call setTranslatesAutoresizingMaskIntoConstraints for.
I have a UIView defined in a .xib file. I need to set translatesAutoresizingMaskIntoConstraints = NO. This means that the frame is not translated to constraints so I need to set the size constraints by myself.
I have created a working category method for a UIView:
-(NSArray*)setSizeConstraints:(CGSize)size
{
NSLayoutConstraint* height = [NSLayoutConstraint constraintWithItem:self attribute:NSLayoutAttributeHeight relatedBy:0 toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:size.height];
NSLayoutConstraint* width = [NSLayoutConstraint constraintWithItem:self attribute:NSLayoutAttributeWidth relatedBy:0 toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:size.width];
[self addConstraint:height];
[self addConstraint:width];
return [NSArray arrayWithObjects:height, width, nil];
}
But I would like to set these constraints from the Xcode interface builder, but all my AutoLayout controls are greyed out:
Is there a way to do this in the interface builder?
This actually is possible.
Simply put the view you'd like to constrain into another view, like the highlighted view here.
Then, add your desired constraints.
Finally, pull the view you just added constraints to out of its parent view. You can now add constraints to that view.
As you've surely found out by now, it looks like there's currently no way to set Autolayout constraints at the main UIView level from Interface Builder.
I had a similar problem here (Launch Screen XIB: Missing Width / Height Constraints (Xcode 6)), while working with the launch screen of my app.
The only workarounds I found, if you want to keep working with IB, are:
Using a UIViewController and its UIView inside the XIB, instead of just a UIView
Working only with Storyboards (and, once again, UIViewController)
However, I understand these approaches may not be ideal or "clean", especially if you simply have a subclass of UIView and you want to draw its interface in a good old XIB.
I'm trying to make constraints programmatically. I have textField and button created in IB. Here is the code:
UIView *superview = self.view;
self.button.translatesAutoresizingMaskIntoConstraints = NO;
self.textField.translatesAutoresizingMaskIntoConstraints = NO;
NSLayoutConstraint *constraint = [NSLayoutConstraint constraintWithItem:self.textField
attribute:NSLayoutAttributeCenterY
relatedBy:NSLayoutRelationEqual
toItem:superview
attribute:NSLayoutAttributeCenterY
multiplier:1.0f
constant:0];
[superview addConstraint:constraint];
constraint = [NSLayoutConstraint constraintWithItem:self.textField
attribute:NSLayoutAttributeCenterX
relatedBy:NSLayoutRelationEqual
toItem:superview
attribute:NSLayoutAttributeCenterX
multiplier:1.0f
constant:0];
[superview addConstraint:constraint];
constraint =[NSLayoutConstraint constraintWithItem:self.button
attribute:NSLayoutAttributeTrailing
relatedBy:NSLayoutRelationEqual
toItem:self.textField
attribute:NSLayoutAttributeLeading
multiplier:1
constant:-10];
[superview addConstraint:constraint];
constraint =[NSLayoutConstraint constraintWithItem:self.button
attribute:NSLayoutAttributeBaseline
relatedBy:NSLayoutRelationEqual
toItem:self.textField
attribute:NSLayoutAttributeBaseline
multiplier:1
constant:0];
[superview addConstraint:constraint];
And after running I have this issue:
Constraints also have no effect on views.
What am I doing wrong?
First in the storyboard editor select the view controller you want to change then, in the constraint editor, select "ADD missing constraints in view controller"
Select an elment that you'd like to modify at runtime by remomiving and adding new constraint, in the object inspector panel select each constraints and edit it by checking the box "placeholder: remove at build time".
This is a way to say to storyboard editor that you are fine with the constraint ant it should not apply or complain about an insufficient constraints situation.
Constraints flagged are removed at runtime, so you should provide you own constraint and is better if you do in the right place. Ovverride -updateViewConstraints in the view controller and remember to call super and add you new constraints.
You have three auto-generated constraints "IB auto generated at build time for view with fixed frame". These conflict with the ones you make yourself. Probably, you have set fixed size properties on the text field and button in Interface Builder. Possibly, you have a fixed width on your button, and that conflicts with the trailing constraint.
Combining IB with code constraints can be tricky. I have found it is often easier to design things only in IB or only in code to avoid conflicts like these, although combining the two is perfectly viable.
For a good explanation on what NSIBPrototypingLayoutConstraint is, have a look at this SO answer:
Trouble with AutoLayout on UITableViewCell
I have created a UIView using the following code within viewDidLoad (where 'secondview' obviously is the name of the UIView):
secondview = [[UIView alloc] initWithFrame:self.view.frame];
[secondview setBackgroundColor: [UIColor yellowColor]];
secondview.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:secondview];
Then within viewDidAppear I added constraints to this view:
NSLayoutConstraint *constraint = [NSLayoutConstraint constraintWithItem:secondview attribute:NSLayoutAttributeRight
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeRight
multiplier:1.0f constant:-20.0f];
[self.view addConstraint:constraint];
However, the constraints are not applied to the view (atleast not that I can see). Instead, the view simply seems to disappear from the screen. If the constraint code is commented out however, the view once again loads with the appropriate frame (obviously without the constraints being applied). When applying the same constraints to a Button or ImageView, the constraints are applied perfectly. This has lead me to think that the issue is because of 'initWithFrame' when creating the View, as neither the button nor ImageView actually require it's size to be specified.
What are your thoughts? What should I do differently?
For anyone who comes across this... I needed to add more than one constraint. That did the trick.