UICollectionView auto scroll to cell at IndexPath

Question

Before loading the collection view user sets the number of image in the array of collection view  All of the cells don t fit on the screen  I have 30 cells and only 6 on the screen   The question  How to scroll to the cell with desired image automatically at the load of UICollectionView

User · Answer

As an alternative to mentioned above  Call after data load   Swift  collectionView reloadData   collectionView layoutIfNeeded   collectionView selectItem at  indexPath  animated  true  scrollPosition   right

User · Answer

All answers here - hacks  I ve found better way to scroll collection view somewhere after relaodData  Subclass collection view layout what ever layout you use  override method prepareLayout  after super call set what ever offset you need  ex  https   stackoverflow com a 34192787 1400119

User · Answer

I would recommend doing it in collectionView  willDisplay  Then you can be sure that the collection view delegate delivers something   Here my example    func collectionView   collectionView  UICollectionView  willDisplay cell  UICollectionViewCell  forItemAt indexPath  IndexPath            this is done to set the index on start to 1 to have at index 0 the last image to have a infinity loop     if  didScrollToSecondIndex           self scrollToItem at  IndexPath row  1  section  0   at   left  animated  false          didScrollToSecondIndex   true

User · Answer

this seemed to work for me  its similar to another answer but has some distinct differences   -  void viewDidLayoutSubviews            self collectionView layoutIfNeeded      NSArray  visibleItems    self collectionView indexPathsForVisibleItems      NSIndexPath  currentItem    visibleItems objectAtIndex 0      NSIndexPath  nextItem    NSIndexPath indexPathForItem someInt inSection currentItem section        self collectionView scrollToItemAtIndexPath nextItem atScrollPosition UICollectionViewScrollPositionNone animated YES

User · Answer

I ve found that scrolling in viewWillAppear may not work reliably because the collection view hasn t finished it s layout yet  you may scroll to the wrong item    I ve also found that scrolling in viewDidAppear will cause a momentary flash of the unscrolled view to be visible    And  if you scroll every time through viewDidLayoutSubviews  the user won t be able to manually scroll because some collection layouts cause subview layout every time you scroll    Here s what I found works reliably   Objective C    -  void viewDidLayoutSubviews        super viewDidLayoutSubviews           If we haven t done the initial scroll  do it once      if   self initialScrollDone            self initialScrollDone   YES            self collectionView scrollToItemAtIndexPath self myInitialIndexPath                                     atScrollPosition UICollectionViewScrollPositionRight animated NO             Swift     override func viewWillLayoutSubviews          super viewWillLayoutSubviews          if   self initialScrollDone              self initialScrollDone   true          self testNameCollectionView scrollToItem at selectedIndexPath  at   centeredHorizontally  animated  true

User · Answer

I totally agree with the above answer  The only thing is that for me the solution was set the code in viewDidAppear  viewDidAppear         self collectionView scrollToItemAtIndexPath indexPath atScrollPosition UICollectionViewScrollPositionCenteredVertically animated YES       When I used the viewWillAppear the scrolling didn t work

User · Answer

You can use GCD to dispatch the scroll into the next iteration of main run loop in viewDidLoad to achieve this behavior  The scroll will be performed before the collection view is showed on screen  so there will be no flashing    -  void viewDidLoad       dispatch async  dispatch get main queue                NSIndexPath  indexPath   YOUR DESIRED INDEXPATH           self collectionView scrollToItemAtIndexPath indexPath atScrollPosition UICollectionViewScrollPositionCenteredHorizontally animated NO

User · Answer

Swift   your CollectionView scrollToItemAtIndexPath indexPath  atScrollPosition  UICollectionViewScrollPosition CenteredHorizontally  animated  true    Swift 3  let indexPath   IndexPath row  itemIndex  section  sectionIndex   collectionView scrollToItem at  indexPath  at  UICollectionViewScrollPosition right  animated  true    Scroll Position   UICollectionViewScrollPosition CenteredHorizontally   UICollectionViewScrollPosition CenteredVertically

User · Answer

New  Edited Answer   Add this in viewDidLayoutSubviews  SWIFT  override func viewDidLayoutSubviews         super viewDidLayoutSubviews       let indexPath   IndexPath item  12  section  0      self collectionView scrollToItem at  indexPath  at    centeredVertically   centeredHorizontally   animated  true      Normally   centerVertically is the case  ObjC  - void viewDidLayoutSubviews       super viewDidLayoutSubviews       NSIndexPath  indexPath    NSIndexPath indexPathForItem 12 inSection 0       self collectionView scrollToItemAtIndexPath indexPath atScrollPosition UICollectionViewScrollPositionCenteredVertically   UICollectionViewScrollPositionCenteredHorizontally animated NO       Old answer working for older iOS  Add this in viewWillAppear    self view layoutIfNeeded    self collectionView scrollToItemAtIndexPath indexPath atScrollPosition UICollectionViewScrollPositionCenteredVertically animated NO

[ios] UICollectionView auto scroll to cell at IndexPath

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