我是 iOS 开发新手。我正在创建一个带有自动布局的聊天应用程序，但每当我在我的应用程序中打开 collectionview 时，我都会遇到“打破约束”。 这是我得到的错误

2017-11-06 07:34:52.838630+0530 ChatHub[4083:306096] [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:0x6040002989c0 BubbleView.width == 205.938   (active, names: BubbleView:0x7ffde3611880 )>",
    "<NSLayoutConstraint:0x604000298600 ProfileImageView.width == 32   (active, names: ProfileImageView:0x7ffde3611a60 )>",
    "<NSLayoutConstraint:0x60400028d890 H:|-(8)-[ProfileImageView](LTR)   (active, names: ProfileImageView:0x7ffde3611a60, '|':ChatHub.ChatMessageCell:0x7ffde360e670 )>",
    "<NSLayoutConstraint:0x6040002988d0 H:[ProfileImageView]-(8)-[BubbleView](LTR)   (active, names: BubbleView:0x7ffde3611880, ProfileImageView:0x7ffde3611a60 )>",
    "<NSLayoutConstraint:0x604000298880 BubbleView.right == ChatHub.ChatMessageCell:0x7ffde360e670.right - 8   (active, names: BubbleView:0x7ffde3611880 )>",
    "<NSLayoutConstraint:0x6000004870d0 'UIView-Encapsulated-Layout-Width' ChatHub.ChatMessageCell:0x7ffde360e670.width == 375   (active)>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x6040002989c0 BubbleView.width == 205.938   (active, names: BubbleView:0x7ffde3611880 )>

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.
2017-11-06 07:34:53.041831+0530 ChatHub[4083:306096] [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:0x600000485c30 BubbleView.width == 205.938   (active, names: BubbleView:0x7ffde345dfb0 )>",
    "<NSLayoutConstraint:0x600000485aa0 ProfileImageView.width == 32   (active, names: ProfileImageView:0x7ffde345e190 )>",
    "<NSLayoutConstraint:0x600000485a00 H:|-(8)-[ProfileImageView](LTR)   (active, names: ProfileImageView:0x7ffde345e190, '|':ChatHub.ChatMessageCell:0x7ffde345b380 )>",
    "<NSLayoutConstraint:0x600000485b40 BubbleView.right == ChatHub.ChatMessageCell:0x7ffde345b380.right - 8   (active, names: BubbleView:0x7ffde345dfb0 )>",
    "<NSLayoutConstraint:0x600000485b90 H:[ProfileImageView]-(8)-[BubbleView](LTR)   (active, names: BubbleView:0x7ffde345dfb0, ProfileImageView:0x7ffde345e190 )>",
    "<NSLayoutConstraint:0x60400029a810 'UIView-Encapsulated-Layout-Width' ChatHub.ChatMessageCell:0x7ffde345b380.width == 375   (active)>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x600000485c30 BubbleView.width == 205.938   (active, names: BubbleView:0x7ffde345dfb0 )>

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.

我该如何解决这个问题。我从过去两天就被困在这里了..请帮忙

i get error in above screenshot but i don't get one in below

最佳答案

据我所知，您对该单元格的水平约束看起来像这样。

H:|-8-[ProfileImageView(=32)]-8-[BubbleView(=206)]-8-|

当 View 的宽度等于其所有 subview 及其周围空间的宽度之和(即 254)时，您的布局几乎没有问题。当单元变宽(或变窄)时，问题就开始了。

在这里您可以看到您配置的宽度与单元格的封装宽度(为 375)冲突。

<NSLayoutConstraint:0x6000004870d0 'UIView-Encapsulated-Layout-Width' ChatHub.ChatMessageCell:0x7ffde360e670.width == 375   (active)>

如果你想保持头像和气泡 View 的宽度固定。我建议您将下面的约束符号 (BubbleView.right) 设置为大于或等于。

<NSLayoutConstraint:0x604000298880 BubbleView.right == ChatHub.ChatMessageCell:0x7ffde360e670.right - 8   (active, names: BubbleView:0x7ffde3611880 )>

另一种选择是确保单元格的宽度始终等于 254，这有点难以实现。

关于ios - 不知道如何防止约束被破坏，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/47128747/