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POAutolayout constraints: Unable to simultaneously satisfy constraints
 

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  1. POAutolayout constraints: Unable to simultaneously satisfy constraints
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    <p>I have an issue with adding a NSLayoutConstraint. I'd like to update the height of an UICollectionView so that all cells fit in the UICollectionView without scrolling. This is because I have put the UICollectionView in a UIScrollView, together with other UI Elements.</p> <p>I have set the constraints in the interface builder, and I resize the UICollectionView on viewDidLoad, when I know how many items should be displayed. I do this with </p> <pre><code>[self allBooksCollectionViewSetConstraints]; </code></pre> <p>I have set</p> <pre><code>[allBooksCollectionView setTranslatesAutoresizingMaskIntoConstraints:NO]; </code></pre> <p>This is my code</p> <pre><code>- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation) fromInterfaceOrientation { [self allBooksCollectionViewConstraints]; } -(NSInteger)allBooksCollectionViewHeight { float booksPerRow; if (UIDeviceOrientationIsPortrait([UIDevice currentDevice].orientation)) { booksPerRow = 6.0; } if (UIDeviceOrientationIsLandscape([UIDevice currentDevice].orientation)) { booksPerRow = 8.0; } //calculate right height do display all cells NSInteger cvHeight = (ceil((float)[allBooksCollectionView numberOfItemsInSection:0]/booksPerRow)*200.0)+49.0; return cvHeight; } -(void)allBooksCollectionViewSetConstraints { NSInteger cvHeight = [self allBooksCollectionViewHeight]; [scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:[NSString stringWithFormat:@"V:[view(%d)]", cvHeight] options:0 metrics:nil views:@{@"view":allBooksCollectionView}]]; } </code></pre> <p>I have tried removing the UICollectionView constraints from the UIScrollview, but it doesn't change a thing.</p> <pre><code>[scrollView removeConstraints:allBooksCollectionView.constraints]; </code></pre> <p>On orientation change I get the following error:</p> <pre><code>Unable to simultaniously satisfy constraints ... ( "&lt;NSLayoutConstraint:0x9aa49f0 V:[UICollectionView:0xc0b6000(849)]&gt;", "&lt;NSLayoutConstraint:0xb2b15d0 V:[UICollectionView:0xc0b6000(1049)]&gt;" ) Will attempt to recover by breaking constraint &lt;NSLayoutConstraint:0xb2b15d0 V:[UICollectionView:0xc0b6000(1049)]&gt; </code></pre> <p>But the other constraint needs to be broken! Not this one, because 1049 is cvHeight.</p> <p>How can I fix this?</p>
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    1. USMathijs
    1. USMathijs
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    1. COyou should only be adding constraints in updateConstraints or updateViewConstraints
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      1. POAutolayout constraints: Unable to simultaneously satisfy constraints
      1. USMax MacLeod
 

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