无法将焦点移动到 tvOS 中的下一个 UICollectionViewCell

Question

我是tvOS应用程序的新手。我在UICollectionView UICollectionViewCell中创建了一个自定义按钮。当我加载视图控制器时，我将焦点转到 UICollectionView 的第一个单元格，但通过按键盘上的下一个键，焦点不会移动到下一个单元格。

我的UICollectionView中有六个不需要滚动的单元格，这意味着这些单元格在UICollectionView的宽度内正确适合。对于六个单元格，我无法将焦点移动到下一个单元格。但是，如果我向 UICollectionView 再添加一个单元格，焦点就会正确移动到下一个单元格。我不确定发生了什么。谁能帮我解决这个问题？

谢谢

Answer 1

我在嵌套集合视图中也有这个。对我来说，问题是内部集合视图没有覆盖-(BOOL)canBecomeFocus并返回NO。

帮助我调试此问题的是打开视图层次结构，获取未聚焦的视图地址（通过右键单击视图的打印说明）并调用po [<view address> _whyIsThisViewNotFocusable]，这很可能会告诉您问题所在。就我而言，它读到：

Printing description of $3:
<_UIStackedImageContainerView: 0x7f9404604630; frame = (0 0; 308 308); layer = <_UIStackedImageContainerLayer: 0x7f94046047d0>>
(lldb) po [0x7f9404604630 _whyIsThisViewNotFocusable]
ISSUE: This view returns NO from -canBecomeFocused.
ISSUE: One or more ancestors have issues that may be preventing this view from being focusable. Details: 
    <StationCollectionViewCell 0x7f940434c6c0>:
        ISSUE: This view returns YES from -canBecomeFocused, which will prevent its subviews from being focusable.
    <StationSectionCollectionViewCell 0x7f940403e8e0>:
        ISSUE: This view returns YES from -canBecomeFocused, which will prevent its subviews from being focusable.

Answer 2

在 Swift 中

如果要聚焦集合视图单元格，则可以使用集合视图委托方法，方法名称为

func collectionView(collectionView: UICollectionView, didUpdateFocusInContext context: UICollectionViewFocusUpdateContext, withAnimationCoordinator coordinator: UIFocusAnimationCoordinator) 
{
}

你可以像这样使用这种方法...

func collectionView(collectionView: UICollectionView, didUpdateFocusInContext context: UICollectionViewFocusUpdateContext, withAnimationCoordinator coordinator: UIFocusAnimationCoordinator) {
if let previousIndexPath = context.previouslyFocusedIndexPath,
let cell = collectionView.cellForItemAtIndexPath(previousIndexPath) {
cell.contentView.layer.borderWidth = 0.0
cell.contentView.layer.shadowRadius = 0.0
cell.contentView.layer.shadowOpacity = 0
}
if let indexPath = context.nextFocusedIndexPath,
let cell = collectionView.cellForItemAtIndexPath(indexPath) {
cell.contentView.layer.borderWidth = 8.0
cell.contentView.layer.borderColor = UIColor.blackColor().CGColor
cell.contentView.layer.shadowColor = UIColor.blackColor().CGColor
cell.contentView.layer.shadowRadius = 10.0
cell.contentView.layer.shadowOpacity = 0.9
cell.contentView.layer.shadowOffset = CGSize(width: 0, height: 0)
collectionView.scrollToItemAtIndexPath(indexPath, atScrollPosition: [.CenteredHorizontally, .CenteredVertically], animated: true)
}
}