如何在我的自定义按钮上显示图像？

Question

我有以下代码，其中包含一些@IBDesignable元素的自定义按钮，但图片未显示。其他一切正常。尝试setImage和setBackgroundImage，但都不想工作。

import UIKit

@IBDesignable

class BigButtonView: UIButton {

    @IBInspectable var borderWidth: CGFloat = 0
    @IBInspectable var borderColor: UIColor = #colorLiteral(red: 0.8039215686, green: 0.9529411765, blue: 0.9647058824, alpha: 1)

    @IBInspectable var gradientColorOne: UIColor = #colorLiteral(red: 0.2588235294, green: 0.8, blue: 0.8352941176, alpha: 1)
    @IBInspectable var gradientColorTwo: UIColor = #colorLiteral(red: 0.3254901961, green: 0.4392156863, blue: 0.8156862745, alpha: 1)

    func setGradientBackground(colorOne: UIColor, colorTwo: UIColor) {

        let gradientLayer = CAGradientLayer()
        gradientLayer.frame = bounds
        gradientLayer.colors = [colorOne.cgColor, colorTwo.cgColor]
        gradientLayer.locations = [0.0, 1.0]
        gradientLayer.startPoint = CGPoint(x: 0.0, y: 0.5)
        gradientLayer.endPoint = CGPoint(x: 1.0, y: 0.5)

        self.layer.insertSublayer(gradientLayer, at: 0)
    }


    let btnImage = UIImage(named: "arrow_right") as UIImage?

    override func awakeFromNib() {
        self.setupView()
    }

    override func prepareForInterfaceBuilder() {
        super.prepareForInterfaceBuilder()
        self.setupView()
    }


    func setupView(){
        self.layer.cornerRadius = self.frame.size.height/2
        self.layer.borderWidth = borderWidth
        self.layer.borderColor = borderColor.cgColor

        self.setTitle("My Button", for: .normal)
        self.titleLabel?.font = UIFont(name: "SFUIDisplay-Regular", size: 22)

        self.setImage(btnImage, for: UIControlState.normal)
        //self.setBackgroundImage(btnImage, for: UIControlState.normal)

        self.layer.masksToBounds = true
        setGradientBackground(colorOne: gradientColorOne, colorTwo: gradientColorTwo)

    }
}