UICollectionView reload data Issue

问题

I have a problem with data reloading using UICollectionView. I have this array on the viewDidLoad to fill the UICollectionView.

array = [[NSMutableArray alloc] init];
[array addObject:@"1"];
[array addObject:@"2"];
[array addObject:@"3"];
[array addObject:@"4"];
[array addObject:@"5"];
[array addObject:@"6"];

and the method:

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    NSString *cellIdentifier = @"Cell";
    //cell = [[UICollectionViewCell alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
    myCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];

    UILabel *titleLabel = [[UILabel alloc] initWithFrame:CGRectMake(5, 0, 100, 20)];
    [titleLabel setText:[array objectAtIndex:indexPath.row]];
    titleLabel.textColor = [UIColor whiteColor];
    titleLabel.backgroundColor = [UIColor clearColor];
    [cell addSubview:titleLabel];

    return cell;
}

I tap the UIButton and data is reloaded:

[myCollectionView reloadData];

Here how the data looks like before and after the reload:

回答1:

You add a new label each time you tap the reload button. You should add the label once and change the label text according.

Here a simple example.

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {

    MyCell *cell = (MyCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"Cell"
                                                                               forIndexPath:indexPath];
    [cell setMyTextLabel:indexPath.row];
    return cell;
}

where MyCell will contains a UILabel and a property to modify its text.

I really suggest to take a look at Fun with UICollectionView code by @Ben Scheirman.

Hope that helps.

P.S. Rename myCell to MyCell. A class should start with an uppercase letter.

回答2:

You are adding your label when you tap reload button. In that case you are adding label again and again...

So there are three solutions:

Make your cell reusable
Remove your cell from superview in reload method.
You can check if label's text length is not equal to zero. In that case no need to add that label and change text.

回答3:

 - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
 {
       UICollectionViewCell *cell=[collectionView dequeueReusableCellWithReuseIdentifier:@"cellIdentifier" forIndexPath:indexPath];
dispatch_async(dispatch_get_main_queue(), ^{

  //  ********* Changed *******

        for (UIView *v in [cell.contentView subviews])
        [v removeFromSuperview];

 // ********** Changed **********
            if ([self.collectionviewFlow.indexPathsForVisibleItems containsObject:indexPath]) {
            NSString *img_name=[NSString stringWithFormat:@"%@_thumb%d.png",self.VaritiesName,(int)indexPath.row+1];
            imageVw=[[UIImageView alloc]initWithImage:[UIImage imageNamed: img_name]];
            imageVw.frame=CGRectMake(10,10,100,100);
            [cell.contentView addSubview:imageVw];
            }
       });
     cell.backgroundColor=[UIColor clearColor];
     return cell;
}

回答4:

It is quit late, but here is my solution.

if you used custom collectionviewcell try to use 'func prepareForReuse()'

来源：https://stackoverflow.com/questions/16517844/uicollectionview-reload-data-issue

标签

ios

objective-c

uicollectionview

uicollectionviewcell