iOS15适配指南

1. UINavigationBar

在iOS 15中，UINavigationBar默认为透明，在滑动时会有模糊效果。如果想一直是模糊效果可以通过设置scrollEdgeAppearance属性来实现。

    let barApp = UINavigationBarAppearance.init()
    barApp.backgroundEffect = UIBlurEffect.init(style: .regular)
    self.navigationBar.scrollEdgeAppearance = barApp*

并且部分旧的navigationBar属性设置无效

• 旧代码

  let navigationBar: UINavigationBar = UINavigationBar.init()
  navigationBar.backgroundColor = .red
  navigationBar.isTranslucent = false
  navigationBar.tintColor = .white
  navigationBar.titleTextAttributes = [
      NSAttributedString.Key.font : UIFont.systemFont(ofSize: 18.0),
      NSAttributedString.Key.foregroundColor : UIColor.white
  ]
  

编译发现，导航栏颜色设置没用作用，呈现白色。导航栏字体颜色设置也没有生效，呈现黑色。查看API发现，iOS 15 UINavigationBar 的相关属性设置需要通过UINavigationBarAppearance来实现。所以需要对iOS 15导航栏进行单独适配。

• 新代码

  if #available(iOS 15, *) {
      let barApp = UINavigationBarAppearance.init()
      barApp.configureWithOpaqueBackground()
      barApp.titleTextAttributes = [
          NSAttributedString.Key.font : UIFont.systemFont(ofSize: 18.0),
          NSAttributedString.Key.foregroundColor : UIColor.white
      ]
      barApp.backgroundColor = .red
      navigationBar.scrollEdgeAppearance = barApp
      navigationBar.standardAppearance = barApp
  }
  

2. UITabBar

UITabBar的问题和UINavigationBar属于同一类，都是部分属性失效

• 旧代码

  let tabBar: UITabBar = UITabBar.init()
  tabBar.backgroundColor = .red
  let tabBarItem: UITabBarItem = UITabBarItem.init()
  let norAttributes = [
      NSAttributedString.Key.font : UIFont.systemFont(ofSize: 18.0),
      NSAttributedString.Key.foregroundColor : UIColor.white
  ]
  let selectedAttributes = [
      NSAttributedString.Key.font : UIFont.systemFont(ofSize: 18.0),
      NSAttributedString.Key.foregroundColor : UIColor.black
  ]
  tabBarItem.setTitleTextAttributes(norAttributes, for: .normal)
  tabBarItem.setTitleTextAttributes(selectedAttributes, for: .selected)
  

同样的UITabBar也需要用UITabBarAppearance来设置属性

• 新代码

  if #available(iOS 15, *) {
      let tabBar: UITabBar = UITabBar.init()
      let tabBarApp = UITabBarAppearance.init()
      tabBarApp.backgroundColor = .red
      let norAttributes = [
          NSAttributedString.Key.font : UIFont.systemFont(ofSize: 18.0),
          NSAttributedString.Key.foregroundColor : UIColor.white
      ]
      let selectedAttributes = [
          NSAttributedString.Key.font : UIFont.systemFont(ofSize: 18.0),
          NSAttributedString.Key.foregroundColor : UIColor.black
      ]
      tabBarApp.stackedLayoutAppearance.normal.titleTextAttributes = norAttributes
      tabBarApp.stackedLayoutAppearance.selected.titleTextAttributes = selectedAttributes
      tabBar.scrollEdgeAppearance = tabBarApp
      tabBar.standardAppearance = tabBarApp    
   }
  

3. UIImage

UIImage新增了几个调整尺寸的方法

    UIImage(named: "")?.preparingThumbnail(of: CGSize.init(width: 100, height: 100))
        // 闭包中直接获取调整后的UIImage（如果失败将返回nil）
    UIImage(named: "")?.prepareThumbnail(of: CGSize.init(width: 200, height: 200), completionHandler: { image in
            // 处理图片
        })
    await UIImage(named: "")?.byPreparingThumbnail(ofSize: CGSize.init(width: 300, height: 300))

4. UITableView

iOS 15对 UITableView新增了sectionHeaderTopPadding作为列表每个部分标题上方的填充，并且它的默认值是UITableViewAutomaticDimension(高度为22)，所以我们要将它的值设置为0，否则TableView section header的高度会增加22像素，适配代码：

    if #available(iOS 15, *) {
        tableView.sectionHeaderTopPadding = 0
    }

5. UIButton新增属性

UIButton支持更多配置，UIButton.configuration是一个新的结构体，它指定按钮以及其内容的外观和行为。如cornerStyle、baseForegroundColor、baseBackgroundColor、buttonSize、title、image、subtitle、titlePadding、imagePadding、contentInsets、imagePlacement等。

    let plain: UIButton = UIButton(configuration: .plain(), primaryAction: nil)
    plain.setTitle("plain", for: .normal)
        
    let tinted: UIButton = UIButton(configuration: .tinted(), primaryAction: nil)
    tinted.setTitle("tinted", for: .normal)
        
    let filled: UIButton = UIButton(configuration: .filled(), primaryAction: nil)
    filled.setTitle("filled", for: .normal)