Question

[buttonCollectionView addConstraint:[NSLayoutConstraint constraintWithItem:maskView
                                                                 attribute:NSLayoutAttributeBottom
                                                                 relatedBy:NSLayoutRelationEqual
                                                                    toItem:buttonCollectionView
                                                                 attribute:NSLayoutAttributeBottom
                                                                multiplier:1.0
                                                                  constant:maskHeight]];

我创建了向UICollectionView添加视图，但为什么它的位置错误？

像这样：UIView: 0x188bbee0; frame = (0 0; 100 5);

CollectionView's frame is: UICollectionView: 0x178b8e00; frame = (0 0; 320 44);

编辑：

添加其他约束

maskView = [[UIView alloc] init];
maskView.backgroundColor = [UIColor colorWithRed:137 / 255.0f green:209 / 255.0f blue:198 / 255.0f alpha:1];
[maskView setTranslatesAutoresizingMaskIntoConstraints:NO];
maskView.translatesAutoresizingMaskIntoConstraints = NO;
[buttonCollectionView addSubview:maskView];
CGFloat maskHeight = 3;
maskXPos = [NSLayoutConstraint constraintWithItem:maskView
                                        attribute:NSLayoutAttributeLeft
                                        relatedBy:NSLayoutRelationEqual
                                           toItem:buttonCollectionView
                                        attribute:NSLayoutAttributeLeft
                                       multiplier:1.0
                                         constant:(CELL_WIDTH - MASK_VIEW_WIDTH) / 2];
[buttonCollectionView addConstraint:maskXPos];
[buttonCollectionView addConstraint:[NSLayoutConstraint constraintWithItem:maskView
                                                                 attribute:NSLayoutAttributeBottom
                                                                 relatedBy:NSLayoutRelationEqual
                                                                    toItem:buttonCollectionView
                                                                 attribute:NSLayoutAttributeBottom
                                                                multiplier:1.0
                                                                  constant:maskHeight]];
[maskView addConstraint:[NSLayoutConstraint constraintWithItem:maskView
                                                     attribute:NSLayoutAttributeWidth
                                                     relatedBy:NSLayoutRelationEqual
                                                        toItem:nil
                                                     attribute:NSLayoutAttributeNotAnAttribute
                                                    multiplier:1.0
                                                      constant:MASK_VIEW_WIDTH]];
[maskView addConstraint:[NSLayoutConstraint constraintWithItem:maskView
                                                     attribute:NSLayoutAttributeHeight
                                                     relatedBy:NSLayoutRelationEqual
                                                        toItem:nil
                                                     attribute:NSLayoutAttributeNotAnAttribute
                                                    multiplier:1.0
                                                      constant:maskHeight]];

Answer 1

对底部尝试此约束：

[buttonCollectionView addConstraint:[NSLayoutConstraint constraintWithItem:buttonCollectionView
                                                                     attribute:NSLayoutAttributeBottom
                                                                     relatedBy:NSLayoutRelationEqual
                                                                        toItem:maskView
                                                                     attribute:NSLayoutAttributeBottom
                                                                    multiplier:1.0
                                                                      constant:0]];//For MaskView's bottom to be aligned with bottom of Collection view distance between two should be '0'

此外，如果你试图以X为中心，你可能会看到NSLayoutAttributeCenterX

Autolayout约束会产生错误的结果

1 个答案: