Question

我在使用具有UILabel的CustomViewCell时遇到一些麻烦。

如果我第一次展示CollectionView，那么一切看起来都像预期的那样。如果UILabel只有一行，则标题位于顶部。但是，如果我开始滚动到列表的末尾而不是返回顶部，则所有UILabels都有两行，有时标题会在中间划分，如

BEFORE：AwesomeTitle

AFTER：Awesom

eTitle

我确定它与reusable Cells有关，但我不知道我做错了什么......

我为单元格设置textLabel，如：

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

    MyItem* a = [self.fetchedResultsController.fetchedObjects objectAtIndex:indexPath.row];
    CustomSelectionView *bookCell = [collectionView dequeueReusableCellWithReuseIdentifier:CustomSelectionCell_IDENTIFIER forIndexPath:indexPath];

    //CELL CONTAINS an UIImage (Cover) and two UILabels (Author, Title)

    //get image from storage
    NSString* isbn = a.isbn;
    NSString* filePath = [_mamPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.jpg", isbn]];

    FDIBookCollectionViewCell* __weak weakCell = bookCell;    
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{

        NSData* data = [NSData dataWithContentsOfFile:filePath];
        UIImage* image = [UIImage imageWithData:data scale:[[UIScreen mainScreen] scale]];

        if (!image) {
            //... handle
        }

        if (image && weakCell) {

            dispatch_async(dispatch_get_main_queue(), ^{
                weakCell.imageView.image = image;
                [weakCell.imageView setNeedsDisplay];
            });

        }

    });


    //set author and title
    bookCell.titelLabel.text = a.titel;

    bookCell.titelLabel.numberOfLines = 2;  //title label can have two lines
    [bookCell.titelLabel sizeToFit];

    return bookCell;
}

InterfaceBuilder for Cell：

enter image description here

BookCell.m

    @implementation FDIBookCollectionViewCell {}

    - (id)initWithFrame:(CGRect)frame
    {
        self = [super initWithFrame:frame];
        if (self) {

        }
        return self;
    }

    //...
    - (void)prepareForReuse {
        [super prepareForReuse];

        self.imageView.image = nil; 
    }

    @end

任何想法？

Answer 1

你很接近，我认为这个问题与在滚动过程中准备好重复使用单元格有关。你已经在prepareForReuse中将图像设置为nil这是好的，你应该只需要将标签设置为nil，这样你的方法就变成了：

-(void)prepareForReuse
{
    [super prepareForReuse];

    self.imageView.image = nil;
    self.titelLabel = nil;   
}

手指交叉应该有效！

编辑：

在自定义单元格标题中，定义setContent方法和标签变量：

-(void)setContentWithDictionary:(NSDictionary *)content;

@property (nonatomic, strong) UILabel *titelLabel;

然后在您的实施文件中：

-(void)setContentWithDictionary:(NSDictionary *)content
{
    //Initialise your labels here
    titelLabel = [[UILabel alloc] init];
    //Customise label and set text
    [titelLabel setText:[content valueForKey:@"CellTitle:]];
}

然后：

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView
                  cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    //Most of your current code
    //Not tested this line, probably won't work as is but you get the idea!
    NSDictionary *cellContent = [NSDictionary dictionaryWithValuesAndKeys:[a.titel], @"CellTitle"];
    CustomSelectionView *bookCell = [collectionView dequeueReusableCellWithReuseIdentifier:CustomSelectionCell_IDENTIFIER forIndexPath:indexPath];
    [bookCell setContent:cellContent];
    return bookCell;
}

对于单元格中的每个其他元素，只需在字典中添加一个新元素即可。这样，每次需要绘制一个单元格时，它都会获得正确的内容，并且标签将以正确的方式设置。

希望这一切都有意义和帮助！

马特

UILabel在Collection Cell中有两行奇怪的行为

1 个答案: