Question

我不断收到一大堆约束警告，但它们似乎只有在通过标签栏控制器转换视图控制器时才会发生。

所以当我使用这段代码时，我没有错误：

let tbc = self.storyboard!.instantiateViewController(withIdentifier: "myViewController") as! myViewController
self.present(tbc, animated: false, completion: nil)

但是当我使用此代码进行转换时，出现了很多错误：

let tbc = self.storyboard!.instantiateViewController(withIdentifier: "MyTabController") as! UITabBarController
tbc.selectedIndex = 1
tbc.modalTransitionStyle = .coverVertical
self.present(tbc, animated: true, completion: nil)

这只是打印到控制台的错误的一个简单：

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.
2017-02-16 19:09:28.038332 ParseStarterProject-Swift[42916:640604] [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. 
    (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) 
(
    "<NSAutoresizingMaskLayoutConstraint:0x60800029e500 h=--& v=--& UIView:0x7fb66b551680.width == 142.8   (active)>",
    "<NSAutoresizingMaskLayoutConstraint:0x60800029e4b0 h=--& v=--& UIView:0x7fb66b551680.height == 140   (active)>",
    "<NSLayoutConstraint:0x60800029be90 UIImageView:0x7fb66b551820.width == UIImageView:0x7fb66b551820.height   (active)>",
    "<NSLayoutConstraint:0x60800029ba80 V:[UIImageView:0x7fb66b551820]-(50)-|   (active, names: '|':UIView:0x7fb66b551680 )>",
    "<NSLayoutConstraint:0x60800029c0c0 V:|-(0)-[UIImageView:0x7fb66b551820]   (active, names: '|':UIView:0x7fb66b551680 )>",
    "<NSLayoutConstraint:0x60800029c110 H:[UIImageView:0x7fb66b551820]-(15)-|   (active, names: '|':UIView:0x7fb66b551680 )>",
    "<NSLayoutConstraint:0x60800029c160 H:|-(15)-[UIImageView:0x7fb66b551820]   (active, names: '|':UIView:0x7fb66b551680 )>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x60800029be90 UIImageView:0x7fb66b551820.width == UIImageView:0x7fb66b551820.height   (active)>

因此，我认为这可能与之相关的唯一约束如下图所示：

enter image description here

我已尝试过符号断点

UIViewAlertForUnsatisfiableConstraints

行动

expr -l objc++ -O -- [[UIWindow keyWindow] _autolayoutTrace]

并获取以下报告，但它不会识别任何约束或UI元素。

•UIWindow:0x7fb66b405490
|   UITransitionView:0x7fb66b516fa0
|   |   UILayoutContainerView:0x7fb66b514e80
|   |   |   UINavigationTransitionView:0x7fb66b613980
|   |   |   |   UIViewControllerWrapperView:0x7fb66b40e580
|   |   UITransitionView:0x7fb66b449f90
|   UITransitionView:0x7fb66b45bd90
|   |   UILayoutContainerView:0x7fb66d831410
|   |   |   UITransitionView:0x7fb66b605eb0
|   |   |   |   UIViewControllerWrapperView:0x7fb66b5567a0
|   |   |   |   |   •UIView:0x7fb66b4300c0
|   |   |   |   |   |   *UICollectionView:0x7fb66b970400
|   |   |   |   |   |   |   •ParseStarterProject_Swift.PackCollectionViewCell:0x7fb66d836fb0
|   |   |   |   |   |   |   |   +UIView:0x7fb66d8371d0
|   |   |   |   |   |   |   |   |   *PFImageView:0x7fb66d837370
|   |   |   |   |   |   |   |   |   *UILabel:0x7fb66d837560'This is a series of breat...'
|   |   |   |   |   |   |   •ParseStarterProject_Swift.PackCollectionViewCell:0x7fb66b4651f0
|   |   |   |   |   |   |   |   +UIView:0x7fb66b465020
|   |   |   |   |   |   |   |   |   *PFImageView:0x7fb66b465410
|   |   |   |   |   |   |   |   |   *UILabel:0x7fb66b465600'Ever had trouble falling ...'
|   |   |   |   |   |   |   •ParseStarterProject_Swift.PackCollectionViewCell:0x7fb66b560e60
|   |   |   |   |   |   |   |   +UIView:0x7fb66b561080
|   |   |   |   |   |   |   |   |   *PFImageView:0x7fb66b561220
|   |   |   |   |   |   |   |   |   *UILabel:0x7fb66b561410'This is a week long intro...'
|   |   |   |   |   |   |   UIImageView:0x7fb66b4305c0
|   |   |   |   |   |   *_UILayoutGuide:0x7fb66b430260
|   |   |   |   |   |   *_UILayoutGuide:0x7fb66b430410
|   |   |   UITabBar:0x7fb66b54c280
|   |   |   |   _UIBarBackground:0x7fb66d830680
|   |   |   |   |   UIImageView:0x7fb66d830b20
|   |   |   |   |   UIVisualEffectView:0x7fb66d830d00
|   |   |   |   |   |   _UIVisualEffectBackdropView:0x7fb66d8310a0
|   |   |   |   |   |   _UIVisualEffectFilterView:0x7fb66b40ddd0
|   |   |   |   |   |   _UIVisualEffectFilterView:0x7fb66b556940
|   |   |   |   UITabBarButton:0x7fb66d82f890
|   |   |   |   |   UITabBarSwappableImageView:0x7fb66b43c280
|   |   |   |   |   UITabBarButtonLabel:0x7fb66d82fb30'Menu'
|   |   |   |   UITabBarButton:0x7fb66b63e100
|   |   |   |   |   UITabBarButtonLabel:0x7fb66b63e3a0
|   |   |   |   UITabBarButton:0x7fb66d830120
|   |   |   |   |   UITabBarSwappableImageView:0x7fb66d828260
|   |   |   |   |   UITabBarButtonLabel:0x7fb66d8303c0'Path'
|   |   |   UIButton:0x7fb66b63e820
|   |   |   |   UIImageView:0x7fb66b4513c0

Legend:
    * - is laid out with auto layout
    + - is laid out manually, but is represented in the layout engine because translatesAutoresizingMaskIntoConstraints = YES
    • - layout engine host

(lldb)

我如何解决这个问题，或者至少如何具体查找报告的实例？它似乎没有任何效果，我已经在多种模拟器尺寸和设备上进行了测试。

Answer 1

尝试使用DEBUG VIEW HIERARCHY解决它有关更多详细信息，请查看以下链接 - 它是解决这些类型的约束问题的最佳解决方案。

Unable to simultaneously satisfy constraints, will attempt to recover by breaking constraint

Answer 2

让tbc = self.storyboard！.instantiateViewController（withIdentifier：“MyTabController”）为！的的UITabBarController

它应该是您的班级名称而不是 UITabBarController

仅在通过TabBarController转换视图时出现约束警告

2 个答案: