http://stackoverflow.com/questions/14523348/how-to-change-the-background-color-of-a-uibutton-while-its-highlighted
UIButton只能设置按下的背景图片，所以我们可以曲线救国，将背景色转换为一张图片
Return an image made from the highlight colour you want. This could also be a category[......]
https://http2.akamai.com/demo[......]
多行文本，如何让UITextView自动换行，且高度自适应
view.addSubview(textView)
let width = UIScreen.main.bounds.width - 40
let size = textView.sizeThatFits(CGSize(width: width, height: CGFloat.greatestFiniteMagnitude))
textView.snp.makeC[......]
private lazy var textField: UITextView = {
let fontSize: CGFloat = 16
let tv = UITextView()
tv.font = UIFont.systemFont(ofSize: fontSize)
tv.textAlignment = .center
var text = NSMutableAttributedString[......]