UITextView 中光标的奇怪定位 [英] weird positioning of the cursor in the UITextView

问题描述

我正在我的 swift 应用程序中从头开始编写不断增长的 UITextView.我在 view 上放了一个 textView 像这样:

I am writing from scratch growing UITextView in my swift app. I put a textView on the view like this:

它就在键盘的正上方.

textView 具有附加到 view 的约束:leading、bottom、top 和 trailing，都等于 4.

The textView has constraints attached to the view: leading, bottom, top and trailing, all equals = 4.

view 具有以下约束:

trailing、leading、bottom、top 和 height

Height 是我代码中的一个出口.我正在检查 textView 中有多少行，并基于此修改 height:

Height is an outlet in my code. I'm checking how many lines are in the textView and based on that I'm modifying height:

func textViewDidChange(textView: UITextView) { //Handle the text changes here
    switch(textView.numberOfLines()) {
    case 1:
        heightConstraint.constant = 38
        break
    case 2:
        heightConstraint.constant = 50
        break
    case 3:
        heightConstraint.constant = 70
        break
    case 4:
        heightConstraint.constant = 90
        break
    default:
        heightConstraint.constant = 90
        break
    }
}

上面的行数是通过这个扩展来计算的:

The number of lines above is calculated by this extension:

extension UITextView{

  func numberOfLines() -> Int{
      if let fontUnwrapped = self.font{
          return Int(self.contentSize.height / fontUnwrapped.lineHeight)
      }
      return 0
  }
}

textView 的初始高度为 38.textView 中的初始字体大小为 15.

The initial height of the textView is 38. The initial font size in the textView is 15.

现在，当用户开始输入新行时，它运行良好，但 textView 未设置在视图的完整范围内.我的意思是，它看起来像这样:

Now, it works nice, when user starts typing new line, but the textView is not set within full bounds of the view. I mean by that the fact, that it looks like this:

它应该是这样的:

为什么要添加这个额外的空白，我该如何摆脱它?

Why there is this extra white space being added and how can I get rid of it?

目前当出现新行时有这个空白，但是当用户滚动 textView 以将文本居中并摆脱空白时 - 它永远消失了，用户无法滚动它再次向上，所以白线在那里.所以对我来说，刷新内容似乎有些问题，但也许你更清楚 - 你能给我一些提示吗?

Currently when new line appears there's this white space, but when user scrolls the textView to center the text and get rid of the white space - it is gone forever, user is not able to scroll it up again so the white line is there. So for me it looks like some problem with refreshing content, but maybe you know better - can you give me some hints?

推荐答案

这是我在我正在开发的一个应用程序的评论部分中使用的一种有点不同的方法.这与 Facebook Messenger iOS 应用程序的输入字段非常相似.更改了插座名称以与您问题中的名称相匹配.

Here is a bit different approach I use in the comment section of one of the apps I'm developing. This works very similar to Facebook Messenger iOS app's input field. Changed outlet names to match with the ones in your question.

//Height constraint outlet of view which contains textView.
@IBOutlet weak var heightConstraint: NSLayoutConstraint!
@IBOutlet weak var textView: UITextView!

//Maximum number of lines to grow textView before enabling scrolling.
let maxTextViewLines = 5
//Minimum height for textViewContainer (when there is no text etc.)
let minTextViewContainerHeight = 40

func textViewDidChange(textView: UITextView) {
    let textViewVerticalInset = textView.textContainerInset.bottom + textView.textContainerInset.top
    let maxHeight = ((textView.font?.lineHeight)! * maxTextViewLines) + textViewVerticalInset
    let sizeThatFits = textView.sizeThatFits(CGSizeMake(textView.frame.size.width, CGFloat.max))

    if sizeThatFits.height < minTextViewContainerHeight {
        heightConstraint.constant = minTextViewContainerHeight
        textView.scrollEnabled = false
    } else if sizeThatFits.height < maxHeight {
        heightConstraint.constant = sizeThatFits.height
        textView.scrollEnabled = false
    } else {
        heightConstraint.constant = maxHeight
        textView.scrollEnabled = true
    }
}

func textViewDidEndEditing(textView: UITextView) {
    textView.text = ""
    heightConstraint.constant = minTextViewContainerHeight
    textView.scrollEnabled = false
}

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