Question

我正在尝试手动添加约束;每次代码尝试添加centerX和centerY约束时，我都会出现以下错误：

由于未捕获的异常终止应用程序＆＃39; NSGenericException＆＃39;，原因：＆＃39;无法在视图上安装约束。是约束引用视图子树外的东西？那＆＃39; S 非法。约束：（有源）＆GT;视图产品：＆gt;＆＃39;

我之前检查过多个问题，但没有任何帮助：/

谢谢 !My code[1]

CODE

[cell.contentView addSubview:imageView];
[cell.contentView addSubview:title];
title.translatesAutoresizingMaskIntoConstraints = NO;
imageView.translatesAutoresizingMaskIntoConstraints = NO;


NSLayoutConstraint *imageViewHeightConstraint = [NSLayoutConstraint
                                                    constraintWithItem:imageView
                                                    attribute:NSLayoutAttributeHeight
                                                    relatedBy:NSLayoutRelationEqual
                                                    toItem:nil
                                                    attribute:NSLayoutAttributeNotAnAttribute
                                                    multiplier:1.0
                                                    constant:[UIScreen mainScreen].bounds.size.width/8];
NSLayoutConstraint *imageViewWidthtConstraint = [NSLayoutConstraint
                                                 constraintWithItem:imageView
                                                 attribute:NSLayoutAttributeWidth
                                                 relatedBy:NSLayoutRelationEqual
                                                 toItem:imageView
                                                 attribute:NSLayoutAttributeHeight
                                                 multiplier:1.0
                                                 constant:0];
NSLayoutConstraint *imageViewCenterXConstraint = [NSLayoutConstraint
                                                 constraintWithItem:imageView
                                                 attribute:NSLayoutAttributeCenterX
                                                 relatedBy:NSLayoutRelationEqual
                                                 toItem:[imageView superview]
                                                 attribute:NSLayoutAttributeCenterX
                                                 multiplier:1.0
                                                 constant:0];

NSLayoutConstraint *imageViewCenterYConstraint = [NSLayoutConstraint
                                                  constraintWithItem:imageView
                                                  attribute:NSLayoutAttributeCenterY
                                                  relatedBy:NSLayoutRelationEqual
                                                  toItem:[imageView superview]
                                                  attribute:NSLayoutAttributeCenterY
                                                  multiplier:1.0
                                                  constant:0];
[imageView addConstraint:imageViewHeightConstraint];
[imageView addConstraint:imageViewWidthtConstraint];
[imageView addConstraint:imageViewCenterXConstraint];
[imageView addConstraint:imageViewCenterYConstraint];

Answer 1

删除addConstraint行并在每次约束实例化后添加.active = YES。同时更改[image superview]

的cell

Answer 2

尝试将centerX和centerY约束添加到imageView的superview，而不是imageView

[cell.contentView addConstraint:imageViewCenterXConstraint]; 
[cell.contentView addConstraint:imageViewCenterYConstraint];

Answer 3

请在向UIImageView添加约束后尝试此操作。

对于目标C

[cell.contentView layoutIfNeeded];
[self.view layoutIfNeeded];

对于Swift

cell.contentView.layoutIfNeeded()
self.view.layoutIfNeeded()

请先尝试一下，先给出约束，然后再将imageView添加到单元格内容中。

Answer 4

为什么不使用：

imageView.center = cell.center

它应该将您的图像置于细胞中心。

Autolayout没有在centerX-centerY上工作

4 个答案: