Swift：UIButton在BarButtonItem中图片变形的解决办法求助

我之前也碰到过一模一样的情况！导航栏的bar button item对自定义视图的尺寸约束经常有点“不听话”，除了设置contentMode = .scaleAspectFit，这几个办法亲测有效：

• 用Auto Layout约束代替frame设置尺寸
  直接设置frame在导航栏环境下很容易被系统覆盖，改用Auto Layout强制锁定按钮的宽高，能确保尺寸稳定：

  let userProfilePic = UIButton(type: .custom)
  userProfilePic.setImage(UIImage(named: "profile_icon.jpg"), for: .normal)
  userProfilePic.contentMode = .scaleAspectFit
  
  // 添加明确的宽高约束
  userProfilePic.widthAnchor.constraint(equalToConstant: 24).isActive = true
  userProfilePic.heightAnchor.constraint(equalToConstant: 24).isActive = true
  
  navigationItem.leftBarButtonItem = UIBarButtonItem(customView: userProfilePic)
  

• 提前将图片缩放到目标尺寸
  把原图预先处理成24x24的大小再赋值给按钮，从根源上避免按钮的缩放逻辑导致变形：

  func resizeImage(to targetSize: CGSize, from originalImage: UIImage) -> UIImage? {
      let renderer = UIGraphicsImageRenderer(size: targetSize)
      return renderer.image { context in
          originalImage.draw(in: CGRect(origin: .zero, size: targetSize))
      }
  }
  
  // 使用示例
  if let originalImage = UIImage(named: "profile_icon.jpg"),
     let resizedImage = resizeImage(to: CGSize(width: 24, height: 24), from: originalImage) {
      let userProfilePic = UIButton(frame: CGRect(x: 0, y: 0, width: 24, height: 24))
      userProfilePic.setImage(resizedImage, for: .normal)
      navigationItem.leftBarButtonItem = UIBarButtonItem(customView: userProfilePic)
  }
  

• 调整按钮的imageEdgeInsets
  有时候图片变形是因为按钮的内边距默认值不合适，通过调整内边距把图片限制在按钮的有效显示区域内：

  let userProfilePic = UIButton(frame: CGRect(x: 0, y: 0, width: 24, height: 24))
  userProfilePic.setImage(UIImage(named: "profile_icon.jpg"), for: .normal)
  userProfilePic.contentMode = .scaleAspectFit
  
  // 根据图片实际比例调整内边距，这里是示例值，你可以按需微调
  userProfilePic.imageEdgeInsets = UIEdgeInsets(top: 2, left: 2, bottom: 2, right: 2)
  
  navigationItem.leftBarButtonItem = UIBarButtonItem(customView: userProfilePic)
  

• 改用UIImageView+手势模拟按钮
  如果UIButton的内部布局逻辑实在不好控制，直接用UIImageView展示图片，再添加手势识别实现点击功能，这种方式更灵活：

  let profileImageView = UIImageView(frame: CGRect(x: 0, y: 0, width: 24, height: 24))
  profileImageView.image = UIImage(named: "profile_icon.jpg")
  profileImageView.contentMode = .scaleAspectFit
  profileImageView.isUserInteractionEnabled = true
  
  // 添加点击手势
  let tapGesture = UITapGestureRecognizer(target: self, action: #selector(handleProfileTap))
  profileImageView.addGestureRecognizer(tapGesture)
  
  navigationItem.leftBarButtonItem = UIBarButtonItem(customView: profileImageView)
  
  // 点击回调方法
  @objc func handleProfileTap() {
      // 这里写你的点击逻辑
  }
  

内容的提问来源于stack exchange，提问作者N. Beer