Ios 在UICollectionView上最多选择4个图像

如果用户选择的图像超过4个，则显示警报框

-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *secell = [collectionView cellForItemAtIndexPath:indexPath];

    if (indexPath.row == 4) {


        UIAlertView * alert =[[UIAlertView alloc ] initWithTitle:@"OK Dailog"
                                                         message:@"This is OK dialog"
                                                        delegate:self
                                               cancelButtonTitle:@"Cancel"
                                               otherButtonTitles: nil];
        [alert show];
    }

    else
    {
        UIImageView *imgselect = (UIImageView *)[secell viewWithTag:110];
        imgselect.image = [UIImage  imageNamed:@"selectimg.png"];
    }

}

您应该检查所选项目的数量，而不是检查indexPath.row。我可以试试这样的

NSArray *selectedIndexPaths =  [collectionView  indexPathsForSelectedItems];

if (selectedIndexPaths.count > 4)
{
   // Show alert
}

---

这应该在委托方法集合视图中设置：shouldSelectItemAtIndexPath

- (BOOL)collectionView:(UICollectionView *)collectionView shouldSelectItemAtIndexPath:(NSIndexPath *)indexPath {
    BOOL shouldSelect = collectionView.indexPathsForSelectedItems.count < 4;
    if (!shouldSelect) {
        // Show Alert
    }
    return shouldSelect;
}