CODEWITHSUNDEEP
objective-cuicollectionview
Karthik Pai
Karthik Pai

Reputation: 597

xcode UICollectionView scroll to default selected item at start

I have created collection view in view controller. I have written code for delegate and datasource methods. Now I want to start the view at a particular index, lets say 2.I have written following code in viewDidLoad method. However, it is throwing exception and my app is getting terminated in the emulator.

NSIndexPath *a=[NSIndexPath indexPathWithIndex:18];
[self.myFullScreenCollectionView scrollToItemAtIndexPath:a atScrollPosition:10 animated:NO];

Upvotes: 0

Views: 3388

Answers (2)

Tarun
Tarun

Reputation: 152

You need to assign a valid enum value in following:

[self.myFullScreenCollectionView scrollToItemAtIndexPath:a atScrollPosition:10 animated:NO];

Here the second parameter needs to be filled with an integer that belongs to following enum UICollectionViewScrollPosition:

typedef NS_OPTIONS(NSUInteger, UICollectionViewScrollPosition) {
    UICollectionViewScrollPositionNone                 = 0,

    // The vertical positions are mutually exclusive to each other, but are bitwise or-able with the horizontal scroll positions.
    // Combining positions from the same grouping (horizontal or vertical) will result in an NSInvalidArgumentException.
    UICollectionViewScrollPositionTop                  = 1 << 0,
    UICollectionViewScrollPositionCenteredVertically   = 1 << 1,
    UICollectionViewScrollPositionBottom               = 1 << 2,

    // Likewise, the horizontal positions are mutually exclusive to each other.
    UICollectionViewScrollPositionLeft                 = 1 << 3,
    UICollectionViewScrollPositionCenteredHorizontally = 1 << 4,
    UICollectionViewScrollPositionRight                = 1 << 5
};

Try using one of these standard enum values, this might help. I think 10 is irrelevant here.

Upvotes: 3

Balram Tiwari
Balram Tiwari

Reputation: 5667

I was struggling to get this work done & now I have it fully functional by using the default method of CollectionView.

Here it is how to scroll the collection view to the respective item index. Let's assume that I want the collection view to scroll to an item at index 3, here is the code.

[self.collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:3 inSection:0]
                            atScrollPosition:UICollectionViewScrollPositionNone
                                    animated:NO];

The key factor was UICollectionViewScrollPositionNone enum value.

Upvotes: 2

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