检测新行在UITextView中启动的时刻

Question

我尝试检测托架在UITextView中的新行.我可以通过比较总后来宽度和UITextView宽度来检测它:

CGSize size = [textView.text sizeWithAttributes:textView.typingAttributes];
if(size.width > textView.bounds.size.width)
      NSLog (@"New line");

但它不能正常工作,因为-sizeWithAttributes:textView只返回没有缩进宽度的字母宽度.请帮忙解决这个问题.

Answer 1

我就是这样做的:

• 获取UITextPosition最后一个角色.
• 打电话caretRectForPosition给你UITextView.
• 创建一个CGRect变量并最初存储CGRectZero在其中.
• 在你的textViewDidChange:方法中,caretRectForPosition:通过传递调用UITextPosition.
• 将其与存储在CGRect变量中的当前值进行比较.如果caretRect的新y原点大于最后一个,则表示已达到新行.

示例代码:

CGRect previousRect = CGRectZero;
- (void)textViewDidChange:(UITextView *)textView{

    UITextPosition* pos = yourTextView.endOfDocument;//explore others like beginningOfDocument if you want to customize the behaviour
    CGRect currentRect = [yourTextView caretRectForPosition:pos];

    if (currentRect.origin.y > previousRect.origin.y){
            //new line reached, write your code
        }
    previousRect = currentRect;

}

此外,您应该在此处阅读UITextInput协议参考文档.这是神奇的,我告诉你.

如果您对此有任何其他问题,请与我们联系.

Answer 2

对于Swift使用此

previousRect = CGRectZero

 func textViewDidChange(textView: UITextView) {

        var pos = textView.endOfDocument
        var currentRect = textView.caretRectForPosition(pos)
        if(currentRect.origin.y > previousRect?.origin.y){
            //new line reached, write your code
        }
        previousRect = currentRect

    }

Answer 3

应允@ n00bProgrammer在Swift-4与更精确的断线检测.

@ n00bProgrammer的答案是完美的,除了一件事,当用户开始输入第一行时,它会有不同的反应,它也提出了这Started New Line一点.
克服问题,这里是精炼的代码

    var previousRect = CGRect.zero
    func textViewDidChange(_ textView: UITextView) {
        let pos = textView.endOfDocument
        let currentRect = textView.caretRect(for: pos)
        self.previousRect = self.previousRect.origin.y == 0.0 ? currentRect : self.previousRect
        if currentRect.origin.y > self.previousRect.origin.y {
            //new line reached, write your code
            print("Started New Line")
        }
        self.previousRect = currentRect
    }