带有自动布局的 UICollectionViewCell 动态高度 [英] UICollectionViewCell dynamic height with autolayout

问题描述

我正在使用 UICollectionViewCell 的自动布局.所以这个想法是允许 CollectionViewCell 根据布局确定它的大小.所有约束都设置正确，但问题是我无法计算数据源方法的大小

I am using auto layout with UICollectionViewCell. So the idea is to allow CollectionViewCell to determine it's size based on layouts. All the constraints are set properly but the problem is that I can not calculate it's size for data source method

collectionView:layout:sizeForItemAtIndexPath:

理想情况下，我想通过以下方式计算 Cell 的高度:

Ideally I would like to calculate Cell's height doing the following:

static MyCell *myCell = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
    myCell = [[MyCell alloc] initWithFrame:CGRectZero];
});
cell.model = model;
[cell updateConstraints];
[cell layoutSubviews];
return cell.frame.size;

但它不会强制更新约束，因此单元格的框架为零.你能告诉我如何根据它的约束来计算单元格的大小吗?

but it doesn't force constraints to update, so the cell's frame is zero. Can you advice me how can I calculate cell's size based on it's constraints?

谢谢

推荐答案

这里是解决方案

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    YourCollectionCell * cell = (YourCollectionCell *) [YourCollectionViewObj cellForItemAtIndexPath:indexPath];

            if (cell == nil) {

                NSArray *topLevelObjects = [[NSBundle mainBundle] loadNibNamed:@"YourCollectionCell" owner:self options:nil];
                cell = [topLevelObjects objectAtIndex:0];
                cell.frame = CGRectMake(0, 0, CGRectGetWidth(self.view.frame), 20);
                // SET YOUR CONTENT
                [cell layoutIfNeeded];

            }

            CGSize CellSize = [cell systemLayoutSizeFittingSize:UILayoutFittingCompressedSize withHorizontalFittingPriority:UILayoutPriorityDefaultHigh verticalFittingPriority:UILayoutPriorityDefaultLow];


            return CellSize;
 }

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