UIView的高度約束打破子視圖的高度約束

我有一個非常簡單的設置，我無法做到我想要的。我正在嘗試添加inputAccessoryView。UIView的高度約束打破子視圖的高度約束

對於inputAccessoryView我有一個UIView（ViewA）配有一個子視圖（ViewB）。 ViewB固定爲ViewA的所有邊緣。 查看B有固定的高度，需要高度爲ViewA和ViewB。

ViewA的不是由我設定，但是0打破ViewB（設定爲42）的高度。

ViewA被添加作爲在UIViewController的視圖一個子視圖並固定在底部和兩個前緣和後緣（ViewA和ViewB的所以寬度應是UIViewController的視圖，其中它是）。

這裏是我的代碼：

override init(frame: CGRect) { 
    super.init(frame: frame) 

    let viewB = UIView() 
    addSubview(viewB) 

    viewB.translatesAutoresizingMaskIntoConstraints = false 
    viewB.topAnchor.constraint(equalTo: topAnchor).isActive = true 
    viewB.leadingAnchor.constraint(equalTo: leadingAnchor).isActive = true 
    viewB.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true 
    viewB.trailingAnchor.constraint(equalTo: trailingAnchor).isActive = true 
    viewB.heightAnchor.constraint(equalToConstant: 42).isActive = true 
}

這將導致以下錯誤：

2017-12-02 15:44:59.150228-0800 Ping[37511:5808904] [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:0x608000283b60 h=--& v=--& MyApp.ViewA:0x7fe606511360.height == 0 (active)>", 
    "<NSLayoutConstraint:0x608000282030 UIView:0x7fe606511550.height == 42 (active)>", 
    "<NSLayoutConstraint:0x608000281d60 V:|-(0)-[UIView:0x7fe606511550] (active, names: '|':MyApp.ViewA:0x7fe606511360)>", 
    "<NSLayoutConstraint:0x608000281ef0 UIView:0x7fe606511550.bottom == MyApp.ViewA:0x7fe606511360.bottom (active)>" 
) 

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x608000282030 UIView:0x7fe606511550.height == 42 (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.

ViewA有一個非常簡單的設置：

extension MessageViewController { 

    open override var canBecomeFirstResponder: Bool { 
     return true 
    } 

    open override var inputAccessoryView: UIView? { 
     return messageInputView 
    } 

}

爲什麼ViewA他我從來沒有設置的ight突破了我設置的限制？

來源

2017-12-02 runmad

@RuslanSerebriakov我已經更新了上面的代碼 – runmad

我認爲解決的辦法是禁用面具自動調整大小爲ViewA：

viewA.translatesAutoresizingMaskIntoConstraints = false

既然你與約束鋪設出來。現在它試圖將您的ViewA的高度設置爲0，從而導致問題。

來源

2017-12-02 23:59:01

我已經添加了一些更多的細節。這是一個'inputAccessoryView'，但即使將其添加爲常規子視圖，也會導致寬度和垂直位置因高度而不明確。 – runmad

所以它的意圖是viewA的高度爲0（就像因爲目前的情況它應該被隱藏）？ –

ViewA應該是其子視圖設置的大小。 – runmad

UIView的高度約束打破子視圖的高度約束

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