iOS Custom Keyboard Extension Autolayout - ios

Question

I'm developing a custom keyboard and i want to use only a UICollectionView as content. The CollectionView should fill (center x and y, width and height available space) of the keyboardview.
My problem is that if i rotate the device the collection view won't be resized.
I tried layout constraints, resizing the view on viewWillTransitionToSize but it does not work. Can anyone give me a hint or show me a way to get this done?

Answer 1

Autolayout should set translatesAutoresizingMaskIntoConstraints to NO before adding Constraint. The code below can make a UICollectionView autolayout with equal edges.
- (void)viewDidLoad {
[super viewDidLoad];
UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];
UICollectionView *collectionView = [[UICollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:layout];
collectionView.translatesAutoresizingMaskIntoConstraints = NO;
collectionView.backgroundColor = [UIColor redColor];
[self.view addSubview:collectionView];
//Adding layout constraint
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:collectionView attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0.0]];
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:collectionView attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterY multiplier:1.0 constant:0.0]];
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:collectionView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeWidth multiplier:1.0 constant:0.0]];
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:collectionView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeHeight multiplier:1.0 constant:0.0]];
}
In addition, I recommend you to use Masonry to build autolayout. In your case, you just need to run the code below to make constraints.
[collectionView mas_makeConstraints:^(MASConstraintMaker *make) {
make.edges.equalTo(self.view);
}];
By the way, autolayout will use more memory then calculating frame yourself. As iOS Keyboard extension has a very harsh memory usage limit (around 40mb depends on your device). If your keyboard would use many memory on process other things, I suggest you don't use autolayout.