CODEWITHSUNDEEP
iosnslayoutconstraint
Eric Chuang
Eric Chuang

Reputation: 1027

How come my constraints are not working? iOS

I am just trying to set a width and a height constraint on my imgView. I have the following code:

UIImageView *imgView = [[UIImageView alloc] init];
imgView.center = self.view.center;
imgView.image = [UIImage imageNamed:@"favorites5-highlighted.png"];
imgView.contentMode = UIViewContentModeCenter;
[self.view addSubview:imgView];

// width constraint
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:[imgView(==100)]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(imgView)]];

// height constraint
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[imgView(==100)]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(imgView)]];

I end up getting this error: Unable to simultaneously satisfy constraints. I looked up SO and tried adding:

imgView.translatesAutoresizingMaskIntoConstraints = NO;

and

self.view.translatesAutoresizingMaskIntoConstraints = NO;

EDIT:

I am just trying to set the width and height of the imageView to the desired properties. I first tried using

CGRect rect = CGRectMake(0, 0, 10, 10);
imgView.frame = rect;

but nothing changed

Upvotes: 2

Views: 3137

Answers (1)

Rob
Rob

Reputation: 437872

Two issues:

  1. You do want:

    imgView.translatesAutoresizingMaskIntoConstraints = NO;

    You do not want:

    self.view.translatesAutoresizingMaskIntoConstraints = NO;

  2. Your attempt to set center is for naught, as when constraints are applied, this will be lost. Unfortunately, you don't define constraints to define the location of the image view. You might do that with the last two lines of the block below:

    UIImageView *imgView = [[UIImageView alloc] init];
//imgView.center = self.view.center;                                // this does nothing in auto layout
imgView.image = [UIImage imageNamed:@"favorites5-highlighted.png"];
imgView.contentMode = UIViewContentModeCenter;
imgView.translatesAutoresizingMaskIntoConstraints = NO;             // add this line
[self.view addSubview:imgView];

NSDictionary *views = NSDictionaryOfVariableBindings(imgView);

// width constraint

[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:[imgView(100)]" options:0 metrics:nil views:views]];

// height constraint

[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[imgView(100)]" options:0 metrics:nil views:views]];

// center align

[self.view addConstraint:[NSLayoutConstraint constraintWithItem:self.view attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:imgView attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0]];
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:self.view attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:imgView attribute:NSLayoutAttributeCenterY multiplier:1.0 constant:0]];

Upvotes: 11

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