ios - 约束冲突 UICollectionView

Question

我收到以下错误输出:

The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2016-05-29 20:02:36.092 City[353:33890] 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:0x1461c600 h=--& v=--& UIView:0x14629380.midX == + 80.2612>",
    "<NSAutoresizingMaskLayoutConstraint:0x1461c630 h=--& v=--& H:[UIView:0x14629380(64.5225)]>",
    "<NSAutoresizingMaskLayoutConstraint:0x1451e6a0 h=--& v=--& UIView:0x1460ac80.midX == + 172.364>",
    "<NSAutoresizingMaskLayoutConstraint:0x1451e6d0 h=--& v=--& H:[UIView:0x1460ac80(283.272)]>",
    "<NSLayoutConstraint:0x1461dbd0 UITextView:0x14b15000'Fabian Delph has been dro...'.leading == UIView:0x14629380.leading + 8>",
    "<NSLayoutConstraint:0x1451e500 UITextView:0x14b15000'Fabian Delph has been dro...'.leading == UIView:0x1460ac80.leading + 8>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x1461dbd0 UITextView:0x14b15000'Fabian Delph has been dro...'.leading == UIView:0x14629380.leading + 8>

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.

我的 UICollectionViewCell 中的所有 View 都是在以下方法中以编程方式创建的，但在 Storyboard中定义的 messageTextView 除外。我知道某些自动调整大小约束存在问题，但我不确定如何解决。如果我在整个单元格上使用 translatesAutoresizingMaskIntoConstraints = false，collectionView 的屏幕上不会显示任何内容。我无法理解 UiView 约束指的是什么，以及我可以做些什么来解决这个问题。

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {

    let cell = collectionView.dequeueReusableCellWithReuseIdentifier("message_cell" , forIndexPath: indexPath) as! DisplayMessageCollectionViewCell

    let textBubbleView: UIView = {
        let view = UIView()
        view.backgroundColor = UIColor(white: 0.95, alpha: 1)
        view.layer.cornerRadius = 15
        view.layer.masksToBounds = true
        return view
    }()
    let profileImageView: UIImageView = {
        let imageView = UIImageView()
        imageView.contentMode = .ScaleAspectFill
        imageView.layer.cornerRadius = 15
        imageView.layer.masksToBounds = true
        imageView.backgroundColor = UIColor.redColor()
        return imageView
    }()
    profileImageView.translatesAutoresizingMaskIntoConstraints = false
    cell.messageTextView.translatesAutoresizingMaskIntoConstraints = false

    //textBubbleView.translatesAutoresizingMaskIntoConstraints = false

    if let messageText =  chat_m[indexPath.row].text {
        cell.messageTextView.text = messageText
        cell.messageTextView.backgroundColor = UIColor.clearColor()
        let sender_image = chat_m[indexPath.row].sender_image
        cell.senderID = chat_m[indexPath.row].sender?.id
        cell.frameView = view
        profileImageView.image = sender_image
        let size = CGSizeMake(250, 1000)
        let options = NSStringDrawingOptions.UsesFontLeading.union(.UsesLineFragmentOrigin)
        let estimatedFrame = NSString(string: messageText).boundingRectWithSize(size, options: options, attributes: [NSFontAttributeName: UIFont.systemFontOfSize(14)], context: nil)
        print(estimatedFrame.width)

        if let user_id = NSUserDefaults.standardUserDefaults().stringForKey("userId") {
            if (user_id == chat_m[indexPath.row].sender?.id) {
                profileImageView.hidden = true
                    cell.messageTextView.frame = CGRectMake(view.frame.width - estimatedFrame.width - 16 - 8, 0, estimatedFrame.width + 16, estimatedFrame.height + 20)
                    textBubbleView.frame = CGRectMake(view.frame.width - estimatedFrame.width - 16 - 8 - 16, -4, estimatedFrame.width + 16 + 8 + 10, estimatedFrame.height + 20 + 6)


                    textBubbleView.backgroundColor = UIColor(red: (69/255.0), green: (209/255.0), blue: (153/255.0), alpha: 1.0)
                    cell.messageTextView.textColor = UIColor.whiteColor()
            }
            else {
                profileImageView.hidden = false
                cell.messageTextView.textColor = UIColor.blackColor()
                textBubbleView.backgroundColor = UIColor(white: 0.95, alpha:1)
                    cell.messageTextView.frame = CGRectMake(48 + 3, 0, estimatedFrame.width + 15, estimatedFrame.height + 20 )
                    textBubbleView.frame = CGRectMake(48, 0, estimatedFrame.width + 20, estimatedFrame.height + 20 )


            }
        }

    }
    cell.addSubview(textBubbleView)
    cell.addSubview(profileImageView)
    cell.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|-4-[v0(30)]", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": profileImageView]))
    cell.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:[v0(30)]|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": profileImageView]))
    cell.sendSubviewToBack(textBubbleView)
    cell.addSubview(profileImageView)
    cell.bringSubviewToFront(profileImageView)
    cell.addConstraint(NSLayoutConstraint(item: cell.messageTextView, attribute: .Trailing, relatedBy: .Equal, toItem: textBubbleView, attribute: .Trailing, multiplier: 1, constant: 0))
    cell.addConstraint(NSLayoutConstraint(item:cell.messageTextView, attribute: .Leading, relatedBy: .Equal, toItem: textBubbleView, attribute: .Leading, multiplier: 1, constant: 8))

    return cell
}

Answer 1

来自您的调试日志:

 "<NSLayoutConstraint:0x1461dbd0 UITextView:0x14b15000'Fabian Delph has been dro...'.leading == UIView:0x14629380.leading + 8>",
 "<NSLayoutConstraint:0x1451e500 UITextView:0x14b15000'Fabian Delph has been dro...'.leading == UIView:0x1460ac80.leading + 8>"

您有两个具有相同值的约束(0x1461dbd0、0x1451e500)绑定(bind)到不同的 View 。这可能会发生冲突。

您的 textBubbleView 有不同的框架，这取决于您的逻辑，并且没有适当的约束(现在它使用默认的 translatesAutoresizingMaskIntoConstraints，其值为 YES)。您有注释行，这是正确的方法，但您还必须按照对 profileImageView 所做的方式为 textBubbleView 设置约束(leading、trailing、top、height - 这取决于您的要求。

如果您希望您的 messageTextView 的布局取决于 textBubbleView - 先删除旧约束并重新添加:

[messageTextView removeConstraints: [messageTextView constraints]];