默认center 模式 居中
btn.contentHorizontalAlignment = UIControl.ContentHorizontalAlignment.right
right 和 trailing效果一样
======= ======= ======= ======= ======= ======= ======= ======= =======
fill
======= ======= ======= ======= ======= ======= ======= ======= =======
leading 和 left 效果一样
if #available(iOS 11.0, *) {
btn.contentHorizontalAlignment = UIControl.ContentHorizontalAlignment.leading
} else {
// Fallback on earlier versions
}
======= ======= ======= ======= ======= ======= ======= ======= =======
======= ======= ======= ======= ======= ======= ======= ======= =======
======= ======= ======= ======= ======= ======= ======= ======= =======