CODEWITHSUNDEEP
iosobjective-cautolayoutnslayoutconstraint
Padin215
Padin215

Reputation: 7484

Autolayout constraints

I need a view to be centered vertically when in portrait mode and moved to the right in landscape (say 150 pixels).

I've tried setting some constraints but can't seem to nail it down:

[myImage addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-(577@700)-[contentView]-(257@800)-|"
                                                                options:0
                                                                metrics:nil
                                                                  views:NSDictionaryOfVariableBindings(contentView)]];

NSLayoutConstraint *myConstraint = [NSLayoutConstraint constraintWithItem:contentView
                                                    attribute:NSLayoutAttributeCenterX
                                                    relatedBy:NSLayoutRelationEqual
                                                       toItem:myImage
                                                    attribute:NSLayoutAttributeCenterX
                                                   multiplier:1.0
                                                     constant:-1];
myConstraint.priority = 700;

[myImage addConstraint:myConstraint];

This works in landscape mode, but not in portrait. In portrait, the left side constraint (570@700) fails, then the left side constraint can succeed (257@800) and the center X is never implemented. I need the first set (570@700 and 257@800) to both fail so it can resort to the center X constraint.

or should i just ditch the centerX constraint?

Upvotes: 2

Views: 803

Answers (1)

John Sauer
John Sauer

Reputation: 4421

I see two options:

  • Add the Constraint that makes contentView's CenterX = myImage's CenterX, and save a reference to the Constraint. When the device rotates to landscape, set the Constraint's constant to 150; when rotated to portrait, set the constant to 0.
  • When the device rotates, remove contentView's horizontal location & size Constraints, and add the appropriate Constraints for your device's orientation.

The first option is simpler, but less future-proof if a new Apple device has different dimensions. If you go with the first option, you won't need the @"H:|-(577)-[contentView]-(257)-|" Constraint, but you will need a Constraint to tell contentView its horizontal size.

Let me know if you'd like me to elaborate on either option.

Upvotes: 2

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