ios - 无法约束将 UIView 固定到单元格 contentView 的底部

Question

在我的应用程序的 UITableViewController 的 cellForRowAtIndexPath: 方法中，我需要将一个编程 UIView 固定到每个单元格各自的 cell.contentView 的底部。这是我的代码:

separatorLineView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320,15)];
separatorLineView.tag = 17;
separatorLineView.backgroundColor = [UIColor colorWithHexString:@"F0F5F7"];
[cell.contentView addSubview:separatorLineView];
[self.separatorLineView setTranslatesAutoresizingMaskIntoConstraints:NO];

NSDictionary* views = NSDictionaryOfVariableBindings(separatorLineView);
NSString *format = @"V:[separatorLineView]-|";


positionYConstraint = [NSLayoutConstraint constraintsWithVisualFormat:format
                                                                  options:0
                                                                  metrics:nil
                                                                    views:views];       

heightConstraint = [NSLayoutConstraint constraintWithItem:postSeparatorLineView
                                                    attribute:NSLayoutAttributeHeight
                                                    relatedBy:NSLayoutRelationEqual
                                                       toItem:cell.contentView
                                                    attribute:NSLayoutAttributeHeight
                                                   multiplier:0.01
                                                     constant:15];


[cell.contentView addConstraints:positionYConstraint];
[cell.contentView addConstraint:heightConstraint];
[cell.contentView layoutSubviews];

当使用 setTranslatesAuto...:NO 行运行时，我看不到 separatorLineView，甚至在 View 调试器中也看不到。当我注释掉该行时，separatorLineView 被设置到 cell.contentView 的顶部。

基本上我需要代码做的就是将 separatorLineView 固定到每个单元格的 contentView 的底部 - 请记住我有动态单元格高度。

Answer 1

你需要水平方向的约束，否则它不会知道它的宽度和x位置。检查这个:

UIView * separatorLineView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320,15)];
separatorLineView.tag = 17;
separatorLineView.backgroundColor = [UIColor colorWithHexString:@"F0F5F7"];    [cell.contentView addSubview:separatorLineView];
[separatorLineView setTranslatesAutoresizingMaskIntoConstraints:NO];

NSDictionary* views = NSDictionaryOfVariableBindings(separatorLineView);
NSString *formatV = @"V:[separatorLineView(==15)]|"; // changed this line to set 15 as height and to really pin your view (note I remove the "-" because it adds a 8 margin)


NSArray *positionYConstraint = [NSLayoutConstraint constraintsWithVisualFormat:formatV
                                                              options:0
                                                              metrics:nil
                                                                views:views];

NSString *formatH = @"H:|[separatorLineView]|"; //these are the missing constraints
NSArray *positionXConstraint = [NSLayoutConstraint constraintsWithVisualFormat:formatH
                                                              options:0
                                                              metrics:nil
                                                                views:views];


[cell.contentView addConstraints:positionYConstraint];
[cell.contentView addConstraints:positionXConstraint];