斯威夫特 UITextView

Question

我正在尝试创建一个 UiTextView，它只能输入 50 个字符，长度不应超过两行，当按下返回时关闭键盘。基于许多 stackover 尝试了各种方法，但似乎没有一个可以解决问题。不确定它必须如此难以做到。任何帮助将不胜感激

目前正在使用

    func textView(textView: UITextView!, shouldChangeTextInRange: NSRange, replacementText: NSString!){
if let range = text.rangeOfCharacterFromSet(NSCharacterSet.newlineCharacterSet()) {
        println("start index: \(range.startIndex), end index: \(range.endIndex)")
    }
    else {
        println("no data")
    }
}

Answer 1

我不确定您所说的“长度不应超过两行”是什么意思，但我可以向您展示如何实现该委托方法以将文本输入限制为 50 个或更少的字符。

func textView(textView: UITextView, shouldChangeTextInRange range: NSRange, replacementText text: String) -> Bool {
    // range contains the range of text that is currently selected, this will be overwritten after this method returned true. If length is 0 nothing will be overwritten
    // text contains the replacement text, might be the empty string "" which indicates deletion

    // current text content of textView must be converted from String to NSString 
    // because stringByReplacingCharactersInRange(...) is a method on NSString
    let currentText = textView.text as NSString

    // do the changes that would happen if this method would return true
    let proposedText = currentText.stringByReplacingCharactersInRange(range, withString: text)
    if countElements(proposedText) > 50 {
        // text would be longer than 50 characters after the changes are applied
        // so ignore any input and don't change the content of the textView
        return false
    }
    // go ahead and change text in the textView
    return true
}

内联 cmets 应该解释所有必要的内容。