水平设置 UICollectionView 的标头时应用程序崩溃 [英] Application crash when set header of UICollectionView horizontally

问题描述

我是 UICollectionView 的新手.我真的很累，想找出解决办法.我正在尝试在 3 个水平行中添加标题.我正在使用集合视图流布局.
这是我实现的代码:

I am pretty new in UICollectionView. And I am really tired to find out the solution. I am trying to add Header in 3 Horizontally Row. I am using Collection view flow layout.
Here is my code which I implement:

    - (void)awakeFromNib {

    self.collectionView.backgroundColor = [UIColor colorWithRed:204.0/255.0 green:204.0/255.0 blue:204.0/255.0 alpha:1.0];

    self.collectionView.backgroundColor = [UIColor clearColor];
    self.collectionView.backgroundView = [[UIView alloc] initWithFrame:CGRectZero];
    UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
    flowLayout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
    flowLayout.itemSize = CGSizeMake(130.0, 170.0);
    [self.collectionView setCollectionViewLayout:flowLayout];

    // Register the colleciton cell
    [_collectionView registerNib:[UINib nibWithNibName:@"ORGArticleCollectionViewCell" bundle:nil] forCellWithReuseIdentifier:@"ORGArticleCollectionViewCell"];
    [self.collectionView registerClass:[_HeaderView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"HeaderView"];
}
#pragma mark - UICollectionViewDataSource methods
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
    return 1;
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    if (section == 0) {
        return [self.collectionData count];
    }
    else if(section == 1)
    {
        return [self.collectionData1 count];
    }
    else
    {
        return [self.collectionData2 count];
    }
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    ORGArticleCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"ORGArticleCollectionViewCell" forIndexPath:indexPath];

    cell.articleTitle.text = [self.collectionData objectAtIndex:[indexPath row]];
    NSString *URL = [self.collectionImageData objectAtIndex:indexPath.row];
    [cell.articleImage setImageWithURL:[NSURL URLWithString:URL] placeholderImage:[UIImage imageNamed:@"profile-image-placeholder"]];
    cell.articleImage.contentMode = UIViewContentModeScaleToFill;
    cell.articlePrice.text = [self.collectionDataPric objectAtIndex:[indexPath row]];
    return cell;
}

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    NSDictionary *cellData = [self.collectionData objectAtIndex:[indexPath row]];
    [[NSNotificationCenter defaultCenter] postNotificationName:@"didSelectItemFromCollectionView" object:cellData];
}
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section
{
    return 0;
}

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section
{
    return 0;
}
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {

    UICollectionReusableView *headerView = [collectionView dequeueReusableSupplementaryViewOfKind:
                                            UICollectionElementKindSectionHeader withReuseIdentifier:@"HeaderView" forIndexPath:indexPath];
    UILabel *label = (UILabel *)[headerView viewWithTag:10];
    if (!label) {
        label = [[UILabel alloc] initWithFrame:CGRectInset(headerView.bounds, 5, 5)];
        label.tag = 10;
        label.font = [UIFont boldSystemFontOfSize:12];
        label.textColor = [UIColor darkGrayColor];
        [headerView addSubview:label];
    }

    label.text = [NSString stringWithFormat:@"Section %d", indexPath.section];
    return headerView;
}

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section {
    CGSize headerSize = CGSizeMake(320, 44);
    return headerSize;
}

当我初始化标题视图时，我的应用程序在 viewForSupplementaryElementOfKind 方法中崩溃.
以下是崩溃日志:

My App crash in viewForSupplementaryElementOfKind method when I initialize the header view.
Following are the crash log:

由于未捕获的异常NSInternalInconsistencyException"而终止应用，原因:-layoutAttributesForSupplementaryElementOfKind 没有 UICollectionViewLayoutAttributes 实例:路径 {length = 2, path = 0 - 0} 处的 UICollectionElementKindSectionHeader"

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'no UICollectionViewLayoutAttributes instance for -layoutAttributesForSupplementaryElementOfKind: UICollectionElementKindSectionHeader at path {length = 2, path = 0 - 0}'

推荐答案

你的代码的问题是 [headerView addSubview:label]; 只有当 label 等于 nil 时才会调用这个.但是每次调用 viewForSupplementaryElementOfKind 时都必须调用此语句.

The problem with your code is [headerView addSubview:label]; this is called only when label is equal to nil. but you have to call this statement every time when viewForSupplementaryElementOfKind is called.

使用以下代码更新您的 viewForSupplementaryElementOfKind 函数.

Update your viewForSupplementaryElementOfKind function with following code.

- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {

    UICollectionReusableView *headerView = [collectionView dequeueReusableSupplementaryViewOfKind:
                                            UICollectionElementKindSectionHeader withReuseIdentifier:@"HeaderView" forIndexPath:indexPath];
    UILabel *label = (UILabel *)[headerView viewWithTag:10];
    if (!label) {
        label = [[UILabel alloc] initWithFrame:CGRectInset(headerView.bounds, 5, 5)];
        label.tag = 10;
        label.font = [UIFont boldSystemFontOfSize:12];
        label.textColor = [UIColor darkGrayColor];

    }
    label.text = [NSString stringWithFormat:@"Section %d", indexPath.section];
    [headerView addSubview:label];
    return headerView;
}

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