我正在尝试为NSLayoutConstraint中的UIImageView设置适当的UITableViewCell。期望的约束如下：
UIImageView是单元格contentView的唯一子视图。我已设置tableView.rowHeight = UITableViewAutomaticDimension和tableView.estimatedRowHeight = 80
2018-03-28 15:52:30.454688-0400 TestApp[28844:694668] [LayoutConstraints] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.
Try this:
(1) look at each constraint and try to figure out which you don't expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
(
"<NSLayoutConstraint:0x604000486cc0 UIImageView:0x7f91cf670470.width == 1.77778*UIImageView:0x7f91cf670470.height (active)>",
"<NSLayoutConstraint:0x604000486e50 H:|-(0)-[UIImageView:0x7f91cf670470] (active, names: '|':UITableViewCellContentView:0x7f91cf66f7e0 )>",
"<NSLayoutConstraint:0x604000486ef0 H:[UIImageView:0x7f91cf670470]-(0)-| (active, names: '|':UITableViewCellContentView:0x7f91cf66f7e0 )>",
"<NSLayoutConstraint:0x604000486f40 V:|-(11)-[UIImageView:0x7f91cf670470] (active, names: '|':UITableViewCellContentView:0x7f91cf66f7e0 )>",
"<NSLayoutConstraint:0x604000486ea0 V:[UIImageView:0x7f91cf670470]-(11)-| (active, names: '|':UITableViewCellContentView:0x7f91cf66f7e0 )>",
"<NSLayoutConstraint:0x604000487530 'UIView-Encapsulated-Layout-Height' UITableViewCellContentView:0x7f91cf66f7e0.height == 233 (active)>",
"<NSLayoutConstraint:0x6040004874e0 'UIView-Encapsulated-Layout-Width' UITableViewCellContentView:0x7f91cf66f7e0.width == 375 (active)>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x604000486cc0 UIImageView:0x7f91cf670470.width == 1.77778*UIImageView:0x7f91cf670470.height (active)>
Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
点击“添加缺失约束”按钮不会添加任何新约束。值1.77778是我的宽高比的正确十进制表示。我不确定为什么运行时需要破坏这个约束。
我还尝试使用Action创建UIViewAlertForUnsatisfiableConstraints的符号断点 - ＆gt;调试器命令expr -l objc++ -O -- [[UIWindow keyWindow] _autolayoutTrace]，我发现打印输出有用，因为它打印整个视图层次结构。我不确定UILayoutGuide的“AMBIGUOUS LAYOUT”与我的UITableView或单元格有什么关系......
•UIWindow:0x7f94bd466e60
| UITransitionView:0x7f94bd64b860
| | •UIView:0x7f94bd468e70
| | | *<UILayoutGuide: 0x6000007bdb20 - "UIViewSafeAreaLayoutGuide", layoutFrame = {{0, 44}, {375, 734}}, owningView = <UIView: 0x7f94bd468e70; frame = (0 0; 375 812); autoresize = W+H; layer = <CALayer: 0x600000822ec0>>>
| | | *UILabel:0x7f94bd469050'Test App'
| | UILayoutContainerView:0x7f94bd610f50
| | | UINavigationTransitionView:0x7f94bd488fa0
| | | | UIViewControllerWrapperView:0x7f94bd6129d0
| | | | | •UIView:0x7f94bd61cea0
| | | | | | *<UILayoutGuide: 0x6040001b7840 - "UIViewSafeAreaLayoutGuide", layoutFrame = {{0, 0}, {375, 690}}, owningView = <UIView: 0x7f94bd61cea0; frame = (0 88; 375 724); autoresize = W+H; layer = <CALayer: 0x6040002370a0>>>
| | | | | | *UITableView:0x7f94be080800
| | | | | | | FancySDK.ImageCell:0x7f94bf025600'5EC2187C-4839-47A3-83E9-C...'
| | | | | | | | •UITableViewCellContentView:0x7f94bd749410
| | | | | | | | | *UIImageView:0x7f94bd749810
| | | | | | | | _UITableViewCellSeparatorView:0x7f94bd749a40
| | | | | | | FancySDK.ArticleCell:0x7f94bd8d9600'18CCDA82-E137-496E-AB0C-5...'
| | | | | | | | •UITableViewCellContentView:0x7f94bd49a0a0
| | | | | | | | | *UIView:0x7f94bd48cfa0
| | | | | | | | | | *UIImageView:0x7f94bd48d180
| | | | | | | | | | *ic_expand:0x7f94bd48d3b0
| | | | | | | | | | *UILabel:0x7f94bd49c210'Apple will unveil the nex...'
| | | | | | | | | | *UILabel:0x7f94bd4a20d0'Apple’s annual Worldwide ...'
| | | | | | | | | | *UILabel:0x7f94bd49ccd0'https://www.theverge.com/...'
| | | | | | | | _UITableViewCellSeparatorView:0x7f94bd4a3990
| | | | | | | UIImageView:0x7f94bd62f410
| | | | | | | UIImageView:0x7f94bd62fbf0
| | | | | | *UIView:0x7f94bd61ccc0
| | | •Recommended for You:0x7f94bd611580
| | | | _UIBarBackground:0x7f94bd614750
| | | | | UIImageView:0x7f94bd615000
| | | | _UINavigationBarLargeTitleView:0x7f94bd50ff60'Recommended for You'
| | | | | UILabel:0x7f94bd4822f0
| | | | •_UINavigationBarContentView:0x7f94bd60ad60'Recommended for You'
| | | | | *<UILayoutGuide: 0x6040001b7e60 - "BackButtonGuide(0x7f94bd60aa00)", layoutFrame = {{0, 0}, {16, 44}}, owningView = <_UINavigationBarContentView: 0x7f94bd60ad60; frame = (0 0; 375 44); layer = <CALayer: 0x604000235ee0>>>
| | | | | *<UILayoutGuide: 0x6040001b7d80 - "LeadingBarGuide(0x7f94bd60aa00)", layoutFrame = {{16, 0}, {24, 44}}, owningView = <_UINavigationBarContentView: 0x7f94bd60ad60; frame = (0 0; 375 44); layer = <CALayer: 0x604000235ee0>>>
| | | | | *<UILayoutGuide: 0x6040001b7ca0 - "TitleView(0x7f94bd60aa00)", layoutFrame = {{46, 0}, {321, 44}}, owningView = <_UINavigationBarContentView: 0x7f94bd60ad60; frame = (0 0; 375 44); layer = <CALayer: 0x604000235ee0>>>
| | | | | *<UILayoutGuide: 0x6040001b7bc0 - "TrailingBarGuide(0x7f94bd60aa00)", layoutFrame = {{367, 0}, {0, 44}}, owningView = <_UINavigationBarContentView: 0x7f94bd60ad60; frame = (0 0; 375 44); layer = <CALayer: 0x604000235ee0>>>
| | | | | *<UILayoutGuide: 0x6040001b7ae0 - "UIViewLayoutMarginsGuide", layoutFrame = {{16, 0}, {343, 44}}, owningView = <_UINavigationBarContentView: 0x7f94bd60ad60; frame = (0 0; 375 44); layer = <CALayer: 0x604000235ee0>>>
| | | | | *_UIButtonBarStackView:0x7f94bd62d8d0
| | | | | | *<UILayoutGuide: 0x6040001b8020 - "UIButtonBar.flexibleSpaceEqualSizeLayoutGuide", layoutFrame = {{0, 0}, {8, 0}}, owningView = <_UIButtonBarStackView: 0x7f94bd62d8d0; frame = (16 0; 24 44); layer = <CALayer: 0x604000237f40>>>- AMBIGUOUS LAYOUT for UILayoutGuide:0x6040001b8020'UIButtonBar.flexibleSpaceEqualSizeLayoutGuide'.minX{id: 446}, UILayoutGuide:0x6040001b8020'UIButtonBar.flexibleSpaceEqualSizeLayoutGuide'.minY{id: 447}, UILayoutGuide:0x6040001b8020'UIButtonBar.flexibleSpaceEqualSizeLayoutGuide'.Width{id: 367}, UILayoutGuide:0x6040001b8020'UIButtonBar.flexibleSpaceEqualSizeLayoutGuide'.Height{id: 448}
| | | | | | *<UILayoutGuide: 0x6040001b81e0 - "UIButtonBar.minimumInterItemSpaceLayoutGuide", layoutFrame = {{0, 0}, {8, 0}}, owningView = <_UIButtonBarStackView: 0x7f94bd62d8d0; frame = (16 0; 24 44); layer = <CALayer: 0x604000237f40>>>- AMBIGUOUS LAYOUT for UILayoutGuide:0x6040001b81e0'UIButtonBar.minimumInterItemSpaceLayoutGuide'.minX{id: 449}, UILayoutGuide:0x6040001b81e0'UIButtonBar.minimumInterItemSpaceLayoutGuide'.minY{id: 450}, UILayoutGuide:0x6040001b81e0'UIButtonBar.minimumInterItemSpaceLayoutGuide'.Height{id: 451}
| | | | | | *<UILayoutGuide: 0x6040001b7a00 - "UIButtonBar.minimumInterGroupSpaceLayoutGuide", layoutFrame = {{0, 0}, {8, 0}}, owningView = <_UIButtonBarStackView: 0x7f94bd62d8d0; frame = (16 0; 24 44); layer = <CALayer: 0x604000237f40>>>- AMBIGUOUS LAYOUT for UILayoutGuide:0x6040001b7a00'UIButtonBar.minimumInterGroupSpaceLayoutGuide'.minX{id: 452}, UILayoutGuide:0x6040001b7a00'UIButtonBar.minimumInterGroupSpaceLayoutGuide'.minY{id: 453}, UILayoutGuide:0x6040001b7a00'UIButtonBar.minimumInterGroupSpaceLayoutGuide'.Height{id: 454}
| | | | | | *<UILayoutGuide: 0x6040001b74c0 - "UIViewLayoutMarginsGuide", layoutFrame = {{0, 0}, {24, 44}}, owningView = <_UIButtonBarStackView: 0x7f94bd62d8d0; frame = (16 0; 24 44); layer = <CALayer: 0x604000237f40>>>
| | | | | | *UIButton:0x7f94bd51de30
| | | | | | | UIImageView:0x7f94bd6210f0
| | | | | *UILabel:0x7f94bd6298a0'Recommended for You'
| | | | +_UINavigationBarModernPromptView:0x7f94bd488da0
| | | | | *UILabel:0x7f94bd4893d0
| | | UIActivityIndicatorView:0x7f94bd531500
| | | | UIImageView:0x7f94bd507950
Legend:
* - is laid out with auto layout
+ - is laid out manually, but is represented in the layout engine because translatesAutoresizingMaskIntoConstraints = YES
• - layout engine host
欢迎任何反馈。谢谢
答案 0 :(得分：1)
问题是宽高比会在不评估为16：9时与其他约束发生冲突。设置前导和尾随约束将评估为特定宽度，同时设置顶部和底部约束将评估为特定高度。比率width：height必须与纵横比相同才能产生冲突。
有几个解决方案。您可能想要的是用水平中心约束替换前导和尾随约束。这将使纵横比决定您的视图在将其置于单元格中时应该有多宽。
更新： 为了阐明宽高比约束的工作原理，它可以作为高度和宽度之间的锁定，强制它们保持它们之间的固定比例。因此，如果您设置其中一个，宽高比约束将有效地为您设置另一个。因此，在具有宽高比约束时，不应设置宽度和高度约束。
答案 1 :(得分：0)
这个问题背后的主要原因是，最初的autolayout假设一个固定的高度（直到计算动态高度）约束（必需）的单元格内容视图与你自己的约束冲突，它出现在这里{{1你可以通过将imageView的底部约束的优先级降低到999而不是1000（必需）来解决这个问题。
解释
您当前的宽度= 375，宽高比= 16/9
然后imageView高度=（375 * 9）/16.0 = 210.9
总= 211 + 11 + 11 = 233> 80（估计好高）