UITextView在键入/不使用故事板时动态更改的高度

我有这个UITextView&我希望它的高度在用户输入时动态改变.我想以编程方式进行.我在另一个UIView上面有UITextView.约束设置如下:

 addtextview.leadingAnchor.constraint(equalTo: addtasktextview.leadingAnchor, constant: 8).isActive = true
      addtextview.trailingAnchor.constraint(equalTo: addtasktextview.trailingAnchor, constant: -8).isActive = true
      addtextview.topAnchor.constraint(equalTo: addtasktextview.topAnchor, constant: 8).isActive = true
      addtextview.bottomAnchor.constraint(equalTo: addtasktextview.bottomAnchor, constant: -40).isActive = true

有趣的是,我也在tableViewCells中使用textview并使用这种约束方法动态地改变高度,但是在这里它不起作用.我希望textview的高度以向上移动的方式增加.因此,当新线开始时,顶部应移动以保持下面的间距.

我该怎么做？帮助将不胜感激.

更新:我能够使用下面的@ upholder-of-truth的答案.我还能够通过查找textview normal height和newSize.height之间的差异,然后将该差异添加到容器的高度来动态更改父UIView容器高度.

首先确保您的类采用UITextViewDelegate协议,以便在文本更改时通知您:

class MyClass: UIViewContoller, UITextViewDelegate

接下来在类中的某处定义此变量,以便您可以跟踪约束中的高度:

var textHeightConstraint: NSLayoutConstraint!

接下来添加以下约束并激活它:

    self.textHeightCOnstraint= addtextview.heightAnchor.constraint(equalToConstant: 40)
    self.textHeightConstraint.isActive = true

(如果你不在viewDidLoad中这样做,你需要使textHeightConstraint成为可选项)

接下来订阅委托(如果尚未完成):

addTextView.delegate = self

添加此函数重新计算高度约束:

func adjustTextViewHeight() {
    let fixedWidth = addtextview.frame.size.width
    let newSize = addtextview.sizeThatFits(CGSize(width: fixedWidth, height: CGFloat.greatestFiniteMagnitude))
    self.textHeightConstraint.cOnstant= newSize.height
    self.view.layoutIfNeeded()
}

接下来,在创建约束后添加对该函数的调用以设置初始大小:

self.adjustTextViewHeight()

最后添加此方法以在文本更改时调整高度:

func textViewDidChange(_ textView: UITextView) {
    self.adjustTextViewHeight()
}

以防这里令人困惑的是UIViewController子类中的一个最小例子:

class ViewController: UIViewController, UITextViewDelegate {
    @IBOutlet var textView: UITextView!
    @IBOutlet var textHolder: UIView!

    var textHeightConstraint: NSLayoutConstraint!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        textView.leadingAnchor.constraint(equalTo: textHolder.leadingAnchor, constant: 8).isActive = true
        textView.trailingAnchor.constraint(equalTo: textHolder.trailingAnchor, constant: -8).isActive = true
        textView.topAnchor.constraint(equalTo: textHolder.topAnchor, constant: 8).isActive = true
        textView.bottomAnchor.constraint(equalTo: textHolder.bottomAnchor, constant: -40).isActive = true

        self.textHeightCOnstraint= textView.heightAnchor.constraint(equalToConstant: 40)
        self.textHeightConstraint.isActive = true

        self.adjustTextViewHeight()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func textViewDidChange(_ textView: UITextView) {
        self.adjustTextViewHeight()
    }

    func adjustTextViewHeight() {
        let fixedWidth = textView.frame.size.width
        let newSize = textView.sizeThatFits(CGSize(width: fixedWidth, height: CGFloat.greatestFiniteMagnitude))
        self.textHeightConstraint.cOnstant= newSize.height
        self.view.layoutIfNeeded()
    }
}