Cannot move focus off of UIButton in UICollectionViewCell

Question

Created Sep ’15

Replies 7

Boosts 0

Views 4.8k

Participants 3

I have a

UICollectionView

of custom

UICollectionViewCell

subclasses, each with a

UILabel

and a

UIButton

. I want to make use of the great default focus behavior of the

UIButton

(since

UICollectionViewCell

s don't have any default focus behavior), so I override the

preferredFocusedView

property of the

UICollectionViewCell

subclass to return the

UIButton

:

@IBOutlet weak var button:UIButton!
@IBOutlet weak var textLabel:UILabel!

override var preferredFocusedView:UIView?
{
     get {
          return self.button
     }
}

override func canBecomeFocused() -> Bool
{
     return true
}

When I do this, I'm unable to move the selection to the next

UICollectionViewCell

. The

context

object of

collectionView(_:didUpdateFocusInContext:withAnimationCoordinator:)

reports that the previous and next

NSIndexPath

s are always (0,0).

If I instead return

self

or

self.textLabel

from

preferredFocusView

and do custom focus appearance changes (like changing the

backgroundColor

of the

UICollectionViewCell

), I'm able to move focus around the

UICollectionView

without problem.

collectionView(_:canFocusItemAtIndexPath:)

has not been overridden. Is there some default behavior of focus in the

UIButton

that I'm overlooking?

Boost

Answer 1

OP

Apple

Sep ’15

This is because when you're trying to focus the next cell it's going Button A -> Cell A -> Button A.

No need to return a preferred focus view for the cell, the focus engine will automatically find the focusable buttons.

0

Answer 2

gfiumara OP

Sep ’15

If

preferredFocusedView

is not overridden to return the

UIButton

, the focus moves around the

UICollectionView

as expected, but the

UIButton

in the

UICollectionViewCell

does not receive focus (does not get the white background with shadow), as evidenced by firings of

collectionView(_:didUpdateFocusInContext:withAnimationCoordinator:)

. The

focused

property of the

UIButton

when moving through the

UICollectionView

(from

nextFocusedIndexPath

) in that delegate method remains

false

.

0

Answer 3

OP

Apple

Sep ’15

Remove the -canBecomeFocused method from your collection view cell and then they won't even be considered for focus.

0

Answer 4

gfiumara OP

Sep ’15

The reason for overriding canBecomeFocused is because the docs say that the default value is false. Regardless, removing the overridden method doesn't change the behavior I'm seeing.

Here's a minimum working example. Reproduce yourself by (project posted separately to avoid moderation):

New Single View project (Obj-C this time).
Change ViewController to a UICollectionViewController.
Swap out Main.storyboard's ViewController for a UICollectionViewController, changing class to ViewController.
Add a new UICollectionViewController subclass.
Populate a single UIButton in the prototype cell in the storyboard, changing the class (to that from step 4) and reuse ID, and adding an outlet to the subclass created in step 4.
Populate required UICollectionViewDataSource methods in ViewController (numberOfItems..., and cellForItem...).
Populate collectionView:didUpdateFocus... to observe focus changes.
Run.

Without overriding preferredFocusView in TestCollectionViewCell, you can move around the UICollectionView fine, but the UIButton (the only view in the cell) never gets focus. If you return the button from preferredFocusedView, the button gets focus, but only in (0,0).

0

Answer 5

gfiumara OP

Sep ’15

Here's the aformentioned example project, which won't be posted for a while due to moderation.

0

Answer 6

mbwksr234 OP

Oct ’15

Accepted Answer

try adding

  override func collectionView(collectionView: UICollectionView, canFocusItemAtIndexPath indexPath: NSIndexPath) -> Bool {
    return false
  }

in addition to not overridding preferredFocusedView

1

Answer 7

gfiumara OP

Oct ’15

This works! This also makes no sense on immediate inspection: the cell cannot obtain focus, but one of its child views can? This lead me to discover something else. UICollectionView has a property, remembersLastFocusedIndexPath, that I set to true. If this is false, I do not need to implement canFocusItemAtIndexPath. Reading the documentation a little more thoroughly, I think I see what may have been happening. A reading of the documentation for this property along with mwhuss's initial reply may reveal that this isn't a bug, but perhaps really strange default behavior (in my opinion).

0