红色条纹是添加到标签图层的边框.

我将标签子类化以添加边缘插入.

override func sizeThatFits(size: CGSize) -> CGSize {
    var size = super.sizeThatFits(size)
    size.width += insets.left + insets.right
    size.height += insets.top + insets.bottom
    return size
}

override func drawTextInRect(rect: CGRect) {
    super.drawTextInRect(UIEdgeInsetsInsetRect(rect,insets))
}

但是,在这种特殊情况下,插入是零.