Alvin Alvin - 1 year ago 121
iOS Question

Auto Layout causes infinite layoutSubviews loop

I'm really puzzled by this, when I use auto layout on a subview the layoutSubview method loops infinitely.

All I'm doing is:

- (id)init
self = [super init];
self.backgroundColor = [UIColor grayColor];
_imageView = [[UIImageView alloc] init];
_imageView.translatesAutoresizingMaskIntoConstraints = NO;
[self addSubview:_imageView];

[self applyConstraints];

return self;

[self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-0-[_imageView]-0-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(_imageView)]];
[self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-0-[_imageView]-0-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(_imageView)]];

And this causes an infinite loop in layoutSubviews. Actually even when applyConstraints is not called the loop occurs, the only way to stop it from happening is setting 'translatesAutoresizingMaskIntoConstraints' to YES.

Has anyone encountered/solved this problem before?

Just to clarify, this is an UIView subclass, which is used within a view controller. The view itself does not use auto layout, instead it's frame is set the old fashioned way after initialization.

Answer Source

The loop was caused by one of the superviews, which was removing its subviews, setting their (possibly new) frame and then re-adding them. As the piece of code was absolutely unnecessary I removed it which fixed the problem.

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