使用UICollectionView创建书架

Question

我打算在我的一个项目中创建一个书架.基本要求如下:

• 类似于iBooks书架
• 很好地支持两种方向
• 支持各种iOS设备(不同的分辨率)
• 支持删除和插入项目
• 支持通过长按手势重新排序项目
• 在第一行被拉下时显示隐藏的徽标

UICollectionView是我遇到的第一个选项.它可以轻松支持网格单元.所以我用Google搜索并发现了一些非常有用的教程:

Bryan Hansen的UICollectionView自定义布局教程

Mark Pospesel的如何将装饰视图添加到UICollectionView

LXReorderableCollectionViewFlowLayout

结果如下:(请忽略颜色不一致问题,因为我选择的图形尚不完美.)

我做了什么:

1. 通过创建从LICReorderableCollectionViewFlowLayout继承的类(用于重新排序)创建自定义布局,该类继承自UICollectionFlowLayout
2. 添加了用于显示徽标的装饰视图
3. 添加了用于显示书架的装饰视图

但是我遇到了一些问题:

如果项目可以在一个屏幕上显示,我根本无法滚动

然后我添加了以下代码,以使contentize更大

- (CGSize)collectionViewContentSize
{
    return CGSizeMake(self.collectionView.bounds.size.width,      self.collectionView.bounds.size.height+100);
}

然后我就可以滚动了.在这里,我拉下第一行:

您可以看到徽标的装饰视图正常工作.

但是当我拉出最后一排时,我遇到了第二组问题:

您可以看到绿色框部分未添加装饰视图.

书架的装饰视图背景越来越暗.(这里请参考同样的问题

当我重新订购商品时,书架栏有时会移动

我在这里列出了一些重要的代码:

- (void)prepareLayout
{
    // call super so flow layout can do all the math for cells, headers, and footers
    [super prepareLayout];

    NSMutableDictionary *dictionary = [NSMutableDictionary dictionary];
    NSMutableDictionary *shelfLayoutInfo = [NSMutableDictionary dictionary];

    // decoration view - emblem
    NSIndexPath *indexPath = [NSIndexPath indexPathForItem:0 inSection:0];
    UICollectionViewLayoutAttributes *emblemAttributes =
        [UICollectionViewLayoutAttributes layoutAttributesForDecorationViewOfKind:[EmblemView kind]
            withIndexPath:indexPath];
    emblemAttributes.frame = [self frameForEmblem:YES];
    dictionary[[EmblemView kind]] = @{indexPath: emblemAttributes};

    // Calculate where shelves go in a vertical layout
    int sectionCount = [self.collectionView numberOfSections];

    CGFloat y = 0;
    CGFloat availableWidth = self.collectionViewContentSize.width - (self.sectionInset.left + self.sectionInset.right);
    int itemsAcross = floorf((availableWidth + self.minimumInteritemSpacing) / (self.itemSize.width + self.minimumInteritemSpacing));

    for (int section = 0; section < sectionCount; section++)
    {
        y += self.headerReferenceSize.height;
        //y += self.sectionInset.top;

        int itemCount = [self.collectionView numberOfItemsInSection:section];
        int rows = ceilf(itemCount/(float)itemsAcross)+1; // add 2 more empty row which doesn't have any data
        for (int row = 0; row < rows; row++)
        {
            indexPath = [NSIndexPath indexPathForItem:row inSection:section];
            shelfLayoutInfo[indexPath] = [NSValue valueWithCGRect:CGRectMake(0,y, self.collectionViewContentSize.width, self.itemSize.height + DECORATION_HEIGHT)];
            y += self.itemSize.height;

            if (row < rows - 1)
                y += self.minimumLineSpacing;
        }

        y += self.sectionInset.bottom;
        y += self.footerReferenceSize.height;
    }

    dictionary[[ShelfView kind]] = shelfLayoutInfo;

    self.shelfLayoutInfo = dictionary;
}


- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
    NSArray *attributesArrayInRect = [super layoutAttributesForElementsInRect:rect];

    // cell layout info
    for (BookShelfLayoutAttributes *attribs in attributesArrayInRect)
    {

        attribs.zIndex = 1;
        CATransform3D t = CATransform3DIdentity;
        t = CATransform3DTranslate(t, 0, 0, 40);
        attribs.transform3D = CATransform3DRotate(t, 15 * M_PI / 180, 1, 0, 0);
    }

    // Add our decoration views (shelves)
    NSMutableDictionary* shelfDictionary = self.shelfLayoutInfo[[ShelfView kind]];
    NSMutableArray *newArray = [attributesArrayInRect mutableCopy];

    [shelfDictionary enumerateKeysAndObjectsUsingBlock:^(id key, NSValue* obj, BOOL *stop) {

        if (CGRectIntersectsRect([obj CGRectValue], rect))
        {
            UICollectionViewLayoutAttributes *attributes = [UICollectionViewLayoutAttributes layoutAttributesForDecorationViewOfKind:[ShelfView kind] withIndexPath:key];
            attributes.frame = [obj CGRectValue];

            NSLog(@"decorationView rect = %@",NSStringFromCGRect(attributes.frame));
            attributes.zIndex = 0;
            //attributes.alpha = 0.5; // screenshots
            [newArray addObject:attributes];
        }
    }];

    attributesArrayInRect = [NSArray arrayWithArray:newArray];

    NSMutableDictionary* emblemDictionary = self.shelfLayoutInfo[[EmblemView kind]];
    NSMutableArray *newArray2 = [attributesArrayInRect mutableCopy];
    [emblemDictionary enumerateKeysAndObjectsUsingBlock:^(NSIndexPath *indexPath, UICollectionViewLayoutAttributes *attributes, BOOL *innerStop) {
        if (CGRectIntersectsRect(rect, attributes.frame)) {
            [newArray2 addObject:attributes];
        }
    }];

    attributesArrayInRect = [NSArray arrayWithArray:newArray2];

    return attributesArrayInRect;
}

如果您有足够的耐心阅读这篇文章并提供任何建议或建议,我将不胜感激.如果我能解决所有问题,我会发布完整的源代码.先感谢您.

Answer 1

我建议检查您的最后一行并对[self.collectionView ScrollEnable:NO]第一行执行相同的操作，将 collectionView 和 collectionViewCell 的背景颜色设置为清晰，并在背景视图上设置书架图像。