UICollectionView刷新了一组新数据

Question

I am trying to delete the entire contents of the collectionView using the following function after reading the apple documentation.

https://developer.apple.com/library/ios/documentation/WindowsViews/Conceptual/CollectionViewPGforIOS/CreatingCellsandViews/CreatingCellsandViews.html#//apple_ref/doc/uid/TP40012334-CH7-SW7

It ends up with the following error.

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid update: invalid number of sections. The number of sections contained in the collection view after the update (0) must be equal to the number of sections contained in the collection view before the update (5), plus or minus the number of sections inserted or deleted (0 inserted, 0 deleted).'

What does this mean? Or can anyone show me a reference link with an example of how to refresh the contents of collectionView with a new set of data on clicking a button.

-(void) clearCollectionViewAndDataArray
{

[self.galleryCollectionView performBatchUpdates:^{
    [displayDataArray removeAllObjects];
    NSLog(@"Is it empty---?%@",displayDataArray);
  [self.galleryCollectionView deleteItemsAtIndexPaths:[self createIndexPathArrayEntireCollectionView]];
}
completion:nil ];
}




-(NSMutableArray*) createIndexPathArrayEntireCollectionView
{

NSMutableArray* indexPathArray = [[NSMutableArray alloc] init];

for(int i=0; i < [displayDataArray count]; i++)
{

    NSMutableArray* sectionArray=[[NSMutableArray alloc] init];
    sectionArray=[displayDataArray objectAtIndex:i];
    for(int j=0; j < [sectionArray count]; j++)
    {
        NSIndexPath* newPath = [NSIndexPath indexPathForRow:j inSection:i];
        [indexPathArray addObject: newPath];
    }

}

return indexPathArray;

}

The NSMutableArray data used is:

(
(
"<SACatalogs: 0x9554750>",
    "<SACatalogs: 0x953d9c0>",
    "<SACatalogs: 0x953e050>"
),
    (
    "<SACatalogs: 0x953e6e0>",
    "<SACatalogs: 0x953ed70>",
    "<SACatalogs: 0x953f420>"
),
    (
    "<SACatalogs: 0x953fab0>",
    "<SACatalogs: 0x9540160>",
    "<SACatalogs: 0x95407f0>"
),
    (
    "<SACatalogs: 0x9540ec0>",
    "<SACatalogs: 0x9541530>",
    "<SACatalogs: 0x9541be0>"
),
    (
    "<SACatalogs: 0x9542290>",
    "<SACatalogs: 0x9542940>",
    "<SACatalogs: 0x9542ff0>"
)
)

The index path used is

"<NSIndexPath 0xa6bb9a0> 2 indexes [0, 0]",
"<NSIndexPath 0xa648bc0> 2 indexes [0, 1]",
"<NSIndexPath 0xa6dcdc0> 2 indexes [0, 2]",
"<NSIndexPath 0xa6c7d00> 2 indexes [1, 0]",
"<NSIndexPath 0xa6c91c0> 2 indexes [1, 1]",
"<NSIndexPath 0xa6f6100> 2 indexes [1, 2]",
"<NSIndexPath 0xa6490d0> 2 indexes [2, 0]",
"<NSIndexPath 0xa6a93b0> 2 indexes [2, 1]",
"<NSIndexPath 0xa6d08b0> 2 indexes [2, 2]",
"<NSIndexPath 0xa64ddb0> 2 indexes [3, 0]",
"<NSIndexPath 0xa6f7380> 2 indexes [3, 1]",
"<NSIndexPath 0xa6c1c90> 2 indexes [3, 2]",
"<NSIndexPath 0xa6e45f0> 2 indexes [4, 0]",
"<NSIndexPath 0xa6bf840> 2 indexes [4, 1]",
"<NSIndexPath 0xa6a03f0> 2 indexes [4, 2]"

}

Thanks in Advance

Answer 1

It seems that you remove all objects from displayDataArray first, and then compute the indexPathArray from displayDataArray . Therefore indexPathArray will be empty and

[self.galleryCollectionView deleteItemsAtIndexPaths:[self createIndexPathArrayEntireCollectionView]];

does nothing . Changing the order to

[self.galleryCollectionView deleteItemsAtIndexPaths:[self createIndexPathArrayEntireCollectionView]];
[displayDataArray removeAllObjects];

could solve the problem. But as mentioned in a comment, you can just call reloadData if all collection view items have been removed.