所以我正在制作消息传递应用程序，我有4个类属性：
-
typingView: UIView! -
messageTextView: UITextView! -
sendButton: UIButton! -
typingViewHeight: NSLayoutConstraint?
typingView是主视图的inputAccessoryView，它有效！它包含messageTextView和sendButton。但是我的问题是...当messageTextView中的文本行数增加时，我希望通过动画> 增加高度(我目前忽略了减少(。这样，我决定更改typingView的高度。
检测内容大小的更改功能完美，我添加了一个观察者 添加此行
messageTextView.addObserver(self, forKeyPath: "contentSize", options: .new, context: nil)
并用这个覆盖
听了override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?)
在此功能中，我有(这是一个过度简化和伪代码，只需假设它有效(
UIView.animate(withDuration: keyboardAnimationDuration) {
self.typingViewHeight?.constaint += (messageTextView.font?.lineHeight)!
}
这是我自定义inputAccessoryView的代码：
lazy var typingViewContainer: UIView = {
// Set up typing view
typingView = UIView(frame: CGRect(x: 0, y: 0, width: self.view.frame.width, height: 55))
typingView.backgroundColor = UIColor.darkGray
typingView.translatesAutoresizingMaskIntoConstraints = false
// Set up animated constraints
typingViewHeight = typingView.heightAnchor.constraint(equalToConstant: typingView.frame.height)
typingViewHeight?.isActive = true
// Set up text view
messageTextView = UITextView()
messageTextView.translatesAutoresizingMaskIntoConstraints = false
messageTextView.font = fakeMessageTextView.font
messageTextView.keyboardType = fakeMessageTextView.keyboardType
messageTextView.isScrollEnabled = fakeMessageTextView.isScrollEnabled
messageTextView.alwaysBounceVertical = fakeMessageTextView.alwaysBounceVertical
messageTextView.text = fakeMessageTextView.text
messageTextView.textColor = fakeMessageTextView.textColor
messageTextView.delegate = self
typingView.addSubview(messageTextView)
// Constraints
messageTextView.bottomAnchor.constraint(equalTo: typingView.bottomAnchor, constant: -fakeMessageTextViewBottom.constant).isActive = true
messageTextView.topAnchor.constraint(equalTo: typingView.topAnchor, constant: fakeMessageTextViewTop.constant).isActive = true
messageTextView.leftAnchor.constraint(equalTo: typingView.leftAnchor, constant: fakeMessageTextViewBottom.constant).isActive = true
messageTextView.widthAnchor.constraint(equalToConstant: fakeMessageTextViewWidth.constant).isActive = true
// Observers
NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow(_:)), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide(_:)), name: NSNotification.Name.UIKeyboardWillHide, object: nil)
messageTextView.addObserver(self, forKeyPath: "contentSize", options: .new, context: nil)
// Set up send button
sendButton = UIButton(type: fakeSendButton.buttonType)
sendButton.translatesAutoresizingMaskIntoConstraints = false
sendButton.setTitle(fakeSendButton.titleLabel?.text!, for: .normal)
sendButton.titleLabel?.font = fakeSendButton.titleLabel?.font
sendButton.titleLabel?.shadowColor = fakeSendButton.titleLabel?.shadowColor
sendButton.addTarget(self, action: #selector(sendPressed(_:)), for: .touchUpInside)
typingView.addSubview(sendButton)
// Constraints
sendButton.heightAnchor.constraint(equalToConstant: fakeSendButtonHeight.constant).isActive = true
sendButton.widthAnchor.constraint(equalToConstant: fakeSendButtonWidth.constant).isActive = true
sendButton.bottomAnchor.constraint(equalTo: typingView.bottomAnchor, constant: -fakeSendButtonBottom.constant).isActive = true
sendButton.rightAnchor.constraint(equalTo: typingView.rightAnchor, constant: -fakeSendButtonRight.constant).isActive = true
return typingView
}()
override var inputAccessoryView: UIView? {
get {
return typingViewContainer
}
}
override var canBecomeFirstResponder: Bool {
get {
return true
}
}
但是，当我测试并输入多行时，它会在控制台中打印出来：
2018-04-25 08:52:57.614383-0500 ProxiChat[3351:168967] [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:0x608000280a50 UIView:0x7f8528a2cda0.height == 73 (active)>",
"<NSLayoutConstraint:0x6040000993c0 UIView:0x7f8528a2cda0.height == 55 (active)>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x608000280a50 UIView:0x7f8528a2cda0.height == 73
(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.
为什么有两个约束？我只添加了一个。请帮忙，谢谢！
编辑
假设我的更改typingView高度的代码有效，因为它在将视图更改为自定义InputAccessoryView之前起作用。我只想知道为什么它打印出该错误，以及如何从设置两个约束中进行修复，即使我只添加了一个？
创建视图时，您将高度设置为55：
typingView = UIView(frame: CGRect(x: 0, y: 0, width: self.view.frame.width, height: 55))
然后您设置一个高度锚：
typingViewHeight = typingView.heightAnchor.constraint(equalToConstant: typingView.frame.height)
typingViewHeight?.isActive = true
这就是为什么您看到冲突的原因。另一个观察结果是，当设置高度锚点时，您可以在其创建的同一行中激活它：
typingViewHeight = typingView.heightAnchor.constraint(equalToConstant: typingView.frame.height).isActive = true
这使您无法每次编写额外的代码
第一件事
而不是观察，我建议您使用UITextView的委托方法来调整容器的高度和文本视图。该代码也有相同的技巧，但我认为它更简洁和干净。
func textViewDidChange(_ textView: UITextView) {
let sizeToFitIn = CGSize(width: textView.bounds.size.width, height: .greatestFiniteMagnitude)
let newSize = textView.sizeThatFits(sizeToFitIn)
var newHeight = newSize.height
....
// That part depends on your approach to placing constraints, it's just my example
textInputHeightConstraint?.constant = newHeight
inputContainerHeightConstraint?.constant = newHeight + (interfaceFactory.inputContainerHeight - interfaceFactory.textInputMinimumHeight)
}
尝试这样更新您的代码：
typingViewHeight = typingView.heightAnchor.constraint(equalToConstant: typingView.frame.height)
typingViewHeight?.priority = UILayoutPriority(rawValue: 999)
typingViewHeight?.isActive = true
如果没有帮助，请查看该答案：https://stackoverflow.com/a/27522511/5147552