带有 UIBarButtonItem LayoutConstraint 问题的 UIToolbar答案

【问题标题】：UIToolbar with UIBarButtonItem LayoutConstraint issue带有 UIBarButtonItem LayoutConstraint 问题的 UIToolbar
【发布时间】：2019-06-14 11:49:16
【问题描述】：

我正在以编程方式创建一个带有 UIBarButtonItem 的 UIToolbar。我没有为此 ViewController 使用 .xib 或故事板。这是我如何创建它的代码。

NSMutableArray *items = [[NSMutableArray alloc] init];

UIBarButtonItem *buttonItem;
buttonItem = [[UIBarButtonItem alloc ] initWithTitle: [Language get:@"Home" alter:nil]
                                               style: UIBarButtonItemStyleBordered
                                              target: self
                                              action: @selector(viewChangeTo)];
[items addObject:buttonItem];

toolbar = [[UIToolbar alloc] init];
toolbar.frame = CGRectMake(0, 0, 1024, 44);
[toolbar setItems:items animated:NO];
[self.view addSubview:toolbar];

每次加载视图时，我都会收到 LayoutConstraints 错误。

[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:0x6000023de350 H:|-(20)-[_UIModernBarButton:0x7fed8c463e00'Home']   (active, names: '|':_UIButtonBarButton:0x7fed8c463bb0 )>",
"<NSLayoutConstraint:0x6000023de3a0 H:[_UIModernBarButton:0x7fed8c463e00'Home']-(20)-|   (active, names: '|':_UIButtonBarButton:0x7fed8c463bb0 )>",
"<NSLayoutConstraint:0x6000023dff70 '_UITemporaryLayoutWidth' _UIButtonBarButton:0x7fed8c463bb0.width == 0   (active)>

Will attempt to recover by breaking constraint

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKitCore/UIView.h> may also be helpful.
2019-01-21 13:14:24.777354+0800 M[50994:10130357] [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:0x6000023de530 _UIModernBarButton:0x7fed8c463e00'Home'.lastBaseline == UILayoutGuide:0x6000039eef40'UIViewLayoutMarginsGuide'.bottom   (active)>",
    "<NSLayoutConstraint:0x6000023de580 V:|-(>=0)-[_UIModernBarButton:0x7fed8c463e00'Home']   (active, names: '|':_UIButtonBarButton:0x7fed8c463bb0 )>",
    "<NSLayoutConstraint:0x6000023e5680 UIButtonLabel:0x7fed8c457e90'Home'.centerY == _UIModernBarButton:0x7fed8c463e00'Home'.centerY + 1.5   (active)>",
    "<NSLayoutConstraint:0x6000023e4c80 '_UITemporaryLayoutHeight' _UIButtonBarButton:0x7fed8c463bb0.height == 0   (active)>",
    "<NSLayoutConstraint:0x6000023de490 'UIView-bottomMargin-guide-constraint' V:[UILayoutGuide:0x6000039eef40'UIViewLayoutMarginsGuide']-(16)-|   (active, names: '|':_UIButtonBarButton:0x7fed8c463bb0 )>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x6000023e5680 UIButtonLabel:0x7fed8c457e90'Home'.centerY == _UIModernBarButton:0x7fed8c463e00'Home'.centerY + 1.5   (active)>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKitCore/UIView.h> may also be helpful.

【问题讨论】：

见stackoverflow.com/questions/47463820/…。我个人认为这是一个 iOS 错误。
我在使用UIToolbar() 创建工具栏时遇到了完全相同的约束错误，如上所述，这是一个 iOS 错误。 @strohtennis 建议的解决方法是将 init 与 CGRect 参数一起使用。

标签： ios objective-c uibarbuttonitem nslayoutconstraint uitoolbar

【解决方案1】：

使用 swift 而不是： let toolbar = UIToolbar()

使用： let toolBar = UIToolbar(frame: CGRect(x: 0, y: 0, width: UIScreen.main.bounds.width, height: 35))

【讨论】：

以上解决了这个问题。似乎低于 12 时的高度值会导致约束问题。我现在按照您的建议使用带有 CGRect 的 init 创建 UIToolbar，将 translateAutoResizingmask 设置为 false 并设置布局约束。