UICollectionView Bounds Width is always 600

问题

I have a custom UIView say CustomView which has a UICollectionView as its SubView. I have added this customView inside a UITableView Prototype Cell and pined all four (top, bottom, left, right) edges to the standard distance with TableViewCell.contentView.

Now i want to set the UICollectionView section insect. In this method - (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section when i get UICollectionView.bounds.width, i always get 600 no matter if i am running it on 4s, 5s, 6 or 6 plus or iPad. This is very annoying and i can't set the proper insect for the UICollectionView section insect. Any help will be great. thanks

Here is my code.

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section {

  NSInteger number = [self collectionView:collectionView numberOfItemsInSection:section];
  NSIndexPath *firstIndexPath = [NSIndexPath indexPathForItem:0 inSection:section];
  CGSize firstSize = [self collectionView:collectionView layout:collectionViewLayout sizeForItemAtIndexPath:firstIndexPath];
  NSIndexPath *lastIndexPath = [NSIndexPath indexPathForItem:number - 1 inSection:section];
  CGSize lastSize = [self collectionView:collectionView layout:collectionViewLayout sizeForItemAtIndexPath:lastIndexPath];
  UIEdgeInsets  insect =  UIEdgeInsetsMake(0, (collectionView.bounds.size.width - firstSize.width) / 2,
                                           0, (collectionView.bounds.size.width - lastSize.width) / 2);

  return insect;

}

here is my initlize of my CustomView which has collectionView as a subView

- (void) initilize {
  UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc ] init];
  flowLayout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
  self.collectionView = [[UICollectionView alloc] initWithFrame:self.bounds collectionViewLayout: flowLayout];
  self.collectionView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
  [self.collectionView registerClass:[PickerCollectionViewCell class] forCellWithReuseIdentifier:@"PickerCollectionViewCell"];
  self.collectionView.delegate = self;
  self.collectionView.dataSource = self;
  self.collectionView.backgroundColor = [UIColor clearColor];
  self.collectionView.showsHorizontalScrollIndicator = NO;
  self.collectionView.allowsMultipleSelection = YES;
  [self addSubview:self.collectionView ];
  self.backgroundColor = [UIColor clearColor];
}

Attached are also two images for my story board.

In the second picture pickerView is my CustomView which contains UICollectionView.

Any help will be great.

回答1:

Width equals 600 because you take it before UIView updates constraint for current screen. You can check UICollectionView frame in - (void)viewDidLayoutSubviews method and you will receive actual value.
Here is two options:
1) You can make insects calculation independent from UICollectionView frame
or
2) You can re-calculate collection view layout after when viewDidLayoutSubviews fires and redraw UICollectionView
(I would rather the first one)

来源：https://stackoverflow.com/questions/34997364/uicollectionview-bounds-width-is-always-600