问UItextfield的rightView中未显示按钮图像

EN

func passwordToggleButton(){
    let button = UIButton(type: .custom)
    button.setImage(UIImage(named: "hidePassword"), for: .normal)
    button.imageEdgeInsets = UIEdgeInsets(top: 0, left: -16, bottom: 0, right: 0)
    button.frame = CGRect(x: CGFloat(txtfPassword.frame.size.width - 25), y: CGFloat(5), width: CGFloat(25), height: CGFloat(25))
    button.backgroundColor = UIColor.white
    button.addTarget(self, action: #selector(self.togglePassword), for: .touchUpInside)
    txtfPassword.rightView = button
    txtfPassword.rightViewMode = .always
}