继承自uiview
class TapAddShowImageView: UIView {
}
重写初始化方法
//code
override init(frame: CGRect) {
        super.init(frame: frame)
        setupSubviews()
    }
//xib
required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setupSubviews()
    }
重写布局方法
override func layoutSubviews() {
        self.showImageView?.frame = self.frame
    }