Autolayout 不适用于 centerX-centerY

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，我都会遇到以下错误：

Terminating app due to uncaught exception 'NSGenericException', reason: 'Unable to install constraint on view. Does the constraint reference something from outside the subtree of the view? That's illegal. constraint: (active)> view:>'

我检查了之前的多个问题，但没有任何帮助：/

谢谢

代码

[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

你为什么不使用：

imageView.center = cell.center

它应该使您的图像在单元格中居中。

Answer 2

尝试将 centerX 和 centerY 约束添加到 imageView 的父视图，而不是 imageView

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

Answer 3

请在为 UIImageView 添加约束后尝试此操作。

对于Objective C

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

对于Swift

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

请先尝试这个，先给出约束，然后将 imageView 添加到单元格 contentView。

Answer 4

删除 addConstraint 行并在约束的每个实例化之后添加 .active = YES。同时将 [image superview] 更改为 cell

Autolayout 不适用于 centerX-centerY

Autolayout not working on centerX- centerY

objective-c

ios

nslayoutconstraint

ios-autolayout