ios - 在 Apple TV 上使用多个控件管理焦点

Question

我的屏幕上有多个控件。右上角的 Collection View ，然后是左中心的按钮，除了按钮，我还有另一个 Collection View 。请引用附图

我能够将焦点从按钮移动到底部 Collection View ，反之亦然。我已经创建了一个焦点指南，如下所示:

        focusGuide.preferredFocusedView = self.btn
        self.view.addLayoutGuide(self.focusGuide)

        self.focusGuide.topAnchor.constraintEqualToAnchor(collectionViewHeader.topAnchor).active = true
        self.focusGuide.bottomAnchor.constraintEqualToAnchor(collectionViewBottom.topAnchor).active = true
        self.focusGuide.leadingAnchor.constraintEqualToAnchor(collectionViewBottom.leadingAnchor).active = true
        self.focusGuide.widthAnchor.constraintEqualToAnchor(collectionViewBottom.widthAnchor).active = true

在 didUpdateFocusInContext: 中，我写了:

    override func didUpdateFocusInContext(context: UIFocusUpdateContext, withAnimationCoordinator coordinator: UIFocusAnimationCoordinator) {
        super.didUpdateFocusInContext(context, withAnimationCoordinator: coordinator)

        guard let nextFocusedView = context.nextFocusedView else { return }

            if(nextFocusedView .isKindOfClass(bottomCell)) {
            self.focusGuide.preferredFocusedView = self.btn
        } else {
            self.focusGuide.preferredFocusedView = self.collectionViewBottom
        }
    }

但是，我无法将焦点从按钮移动到顶级 Collection View 。为此，我可能需要多个焦点指南，但我不知道那里应该有什么。谁可以帮我这个事？

谢谢

Answer 1

我在 UI 的许多部分都遇到了类似的问题，因此最终定义了一个自定义 View 来创建更大的屏幕区域来表示可聚焦控件组。因为我设置了这些较大的区域来覆盖不包含控件的空白区域，所以它们会拦截焦点移动并将焦点转移到区域内的控件，而与焦点开始的原始控件的垂直或水平对齐无关。

这是自定义 View 。您可以通过在 IB 中放置一个或多个控件来使用它。

请注意，它具有其他功能，例如无需覆盖 preferredFocusView 即可将焦点强制到特定控件，但如果不需要它们，您可以删除它们)。

class FocusGroup : UIView
{
   weak private var nextFocusView:UIView? = nil
   weak var initialView:UIView?           = nil
   var captureFocus:Bool                  = false

   func focusOnView(view:UIView, now:Bool=false)
   {
      if not(view.isDescendantOfView(self))
      || view === self
      { return }

      nextFocusView = view
      setNeedsFocusUpdate()
      if now  { updateFocusIfNeeded() }
   }

   func resetFocus(now now:Bool=false)
   {
      nextFocusView = nil
      setNeedsFocusUpdate()
      if now  { updateFocusIfNeeded() }
   }

   override func canBecomeFocused() -> Bool 
   {
      if nextFocusView != nil { return true }
      if containsFocus { return false }      
      return firstFocusableSubView() != nil 
   }


   func firstFocusableSubView() -> UIView?
   {

     return findSubview({ 
                           $0.canBecomeFocused()
                           && $0.userInteractionEnabled
                           && $0.visible
                           &&  ( not($0 is UIButton)
                                 || ($0 as! UIButton).enabled )
                       })
   }


   override var preferredFocusedView: UIView? 
   {
      if let viewToFocus = ( nextFocusView ?? initialView ) ?? firstFocusableSubView() 
      {
        return viewToFocus
      }
      return nil
   }

   override func shouldUpdateFocusInContext(context: UIFocusUpdateContext) -> Bool 
   {
      // when capturing focus, prevent navigation outside of grouped subviews
      if captureFocus 
      && containsFocus 
      && context.previouslyFocusedView!.isDescendantOfView(self)
      && (
            context.nextFocusedView == nil
            || context.nextFocusedView === self 
            || not(context.nextFocusedView!.isDescendantOfView(self))
         )
      { return false }

      return true
   }

   override func didUpdateFocusInContext(context: UIFocusUpdateContext, withAnimationCoordinator coordinator: UIFocusAnimationCoordinator) 
   {
      // give focus to specific view as requested
      if nextFocusView != nil
      {
         if context.nextFocusedView === nextFocusView
         || not(nextFocusView!.canBecomeFocused())
         { nextFocusView = nil }
         return
      }      
   }

}