iOS 11大 Headers 更改事件

3 回答

• 1

  它可以通过scrollViewDidScroll func获取UINavigationBar的当前高度来完成 .

  func scrollViewDidScroll(_ scrollView: UIScrollView) {
  
      //Get current height of navigation bar when tableview/collectionview/scrollview did scroll
      guard let navBarHeight = navigationController?.navigationBar.frame.height else {
          return
      }
  
      //Compare with standard height of navigation bar.
      if navBarHeight > 44.0 {
          self.navigationController?.navigationBar.shadowImage = UIImage()
          self.navigationController?.navigationBar.setBackgroundImage(UIImage(), for: .default)
          self.navigationController?.navigationBar.barTintColor = .clear
      } else {
          self.navigationController?.navigationBar.shadowImage = nil
          self.navigationController?.navigationBar.setBackgroundImage(nil, for: .default)
          self.navigationController?.navigationBar.barTintColor = .green
      }
  }
  

  回复于 2024-04-28T18:32:24+08:00
• 2

  Piyush Hirpara答案（关于性能）的一个小改进是子类化您的navigationBar并且仅在 layoutSubviews 上更新：

  class ObservingLargeTitleNavigationBar: UINavigationBar {
  
      override func layoutSubviews() {
          super.layoutSubviews()
  
          updateLargeTitle()
      }
  
      private func updateLargeTitle() {
          if #available(iOS 11.0, *) {
              if frame.height >= 44 {
                  // code logic when large title is visible
              } else {
                  // code logic when large title is hidden
              }
          }
      }
  }
  

  请注意，在某些情况下可能需要调整 frame.height 的 44 的值 . 我在 60 有它，例如我在iPhone X上的配置 .

  回复于 2024-04-28T18:32:24+08:00
• 2

  我在UIViewController的子类的ViewWillAppear中添加了这个观察者 . 并根据其高度设置颜色如下：

  在ViewWillAppear中：

  UINavigationBar *navBar = self.navigationController.navigationBar;
  [navBar addObserver:self forKeyPath:@"frame" options:NSKeyValueObservingOptionNew context:nil];
  

  在viewWillDisappear中：

  UINavigationBar *navBar = self.navigationController.navigationBar;
  [navBar removeObserver:self forKeyPath:@"frame" context:NULL];
  
  - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
  if ([keyPath isEqualToString:@"frame"]) {
      [self setNavigationBarColour];;
  }
  

  }

  - (void)setNavigationBarColour
  {
      UINavigationBar *navBar = self.navigationController.navigationBar;
      CGFloat height = navBar.bounds.size.height;
      if(height>44)
      {
          [navBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
          [navBar setTranslucent:YES];
          [navBar setShadowImage:[UIImage new]];
      }
      else
      {
          [navBar setBackgroundImage:[[UINavigationBar appearance] backgroundImageForBarMetrics:UIBarMetricsDefault] forBarMetrics:UIBarMetricsDefault];
          [navBar setTranslucent:NO];
          [navBar setShadowImage:[[UINavigationBar appearance] shadowImage]];
      }
  }
  

  回复于 2024-04-28T18:32:24+08:00