drawrect - 使用drawRect绘制的collectionView :cellForItemAtIndexPath mixes up images,:

Question

为了提高性能，我决定使用 drawRect: 绘制 UICollectionViewCell，而不是自定义 xib 文件(因为我有阴影和标签阴影)。

出于某种原因，自从我更改了此设置后，我的单元格每次重新加载到 UICollectionView 中时都不会使用不同的图像进行绘制。

当我记录图像的名称时，它被设置为在 collectionView:cellForItemAtIndexPath 和 drawRect: 中加载，它提供了正确的图像名称和正确的索引路径，但是当我加载应用程序时，它会在滚动时混淆它们，即使最初它们已正确加载。

这是我的代码:

viewDidLoad

//  Collection cells
//
[self.collectionView registerClass:[CluelessSymbolCell class] forCellWithReuseIdentifier:@"Symbol cell"];

collectionView:cellForItemAtIndexPath

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

    CluelessClue *clue = [self.clues objectAtIndex:indexPath.row];

    NSLog(@"(%@) Image: %@", indexPath, [clue.imageNames objectAtIndex:0]);

    [cell setClue:clue];

    return cell;
}

drawRect:(在单元格子类“CluelessSymbolCell”中)

- (void)drawRect:(CGRect)rect
{
    NSString *imageName = [NSString stringWithFormat:@"%@-icon-iphone", [self.clue.imageNames objectAtIndex:0]];

    //  Cell
    //
    [self.contentView.layer setShadowColor:[UIColor blackColor].CGColor];
    [self.contentView.layer setShadowOpacity:0.3f];
    [self.contentView.layer setShadowRadius:2.0f];
    [self.contentView.layer setShadowOffset:CGSizeZero];
    [self.contentView.layer setShadowPath:[UIBezierPath bezierPathWithRect:self.layer.bounds].CGPath];

    //      Image
    //
    CALayer *imageLayer = [CALayer layer];
    [imageLayer setFrame:rect];
    [imageLayer setContents:(id)[[UIImage imageNamed:imageName] CGImage]];

    [self.contentView.layer addSublayer:imageLayer];
}

编辑

在记录单元格内容 View 的子层时，我可以看到每个单元格的内容 View 子层已移动到下一个单元格，这是什么原因以及如何克服它？

日志:

2013-02-22 23:41:08.064 Clueless[3462:c07] <NSIndexPath 0x845cb90> 2 indexes [0, 0], (null)
2013-02-22 23:41:08.065 Clueless[3462:c07] <NSIndexPath 0x84435f0> 2 indexes [0, 1], (null)
2013-02-22 23:41:08.066 Clueless[3462:c07] <NSIndexPath 0x8446f50> 2 indexes [0, 2], (null)
2013-02-22 23:41:08.066 Clueless[3462:c07] <NSIndexPath 0x843a060> 2 indexes [0, 3], (null)
2013-02-22 23:41:08.067 Clueless[3462:c07] <NSIndexPath 0x846bc70> 2 indexes [0, 4], (null)
2013-02-22 23:41:08.067 Clueless[3462:c07] <NSIndexPath 0x845cd20> 2 indexes [0, 5], (null)
2013-02-22 23:41:08.068 Clueless[3462:c07] <NSIndexPath 0x845ce60> 2 indexes [0, 6], (null)
2013-02-22 23:41:08.068 Clueless[3462:c07] <NSIndexPath 0x846ce40> 2 indexes [0, 7], (null)
2013-02-22 23:41:08.069 Clueless[3462:c07] <NSIndexPath 0x846c9b0> 2 indexes [0, 8], (null)
2013-02-22 23:41:08.069 Clueless[3462:c07] <NSIndexPath 0x846d880> 2 indexes [0, 9], (null)
2013-02-22 23:41:08.070 Clueless[3462:c07] <NSIndexPath 0x846db20> 2 indexes [0, 10], (null)
2013-02-22 23:41:08.071 Clueless[3462:c07] <NSIndexPath 0x846df30> 2 indexes [0, 11], (null)
2013-02-22 23:41:15.105 Clueless[3462:c07] <NSIndexPath 0x846ec60> 2 indexes [0, 12], (null)
2013-02-22 23:41:15.106 Clueless[3462:c07] <NSIndexPath 0x846efb0> 2 indexes [0, 13], (null)
2013-02-22 23:41:15.107 Clueless[3462:c07] <NSIndexPath 0x846f6d0> 2 indexes [0, 14], (null)
2013-02-22 23:41:15.753 Clueless[3462:c07] <NSIndexPath 0x82492e0> 2 indexes [0, 15], (
    "<CALayer: 0x8495840>"
)
2013-02-22 23:41:15.754 Clueless[3462:c07] <NSIndexPath 0x827f750> 2 indexes [0, 16], (
    "<CALayer: 0x8491010>"
)
2013-02-22 23:41:15.754 Clueless[3462:c07] <NSIndexPath 0x827f5c0> 2 indexes [0, 17], (
    "<CALayer: 0x8493ef0>"
)
2013-02-22 23:41:15.986 Clueless[3462:c07] <NSIndexPath 0x845cb90> 2 indexes [0, 0], (
    "<CALayer: 0x8493ef0>"
)
2013-02-22 23:41:15.987 Clueless[3462:c07] <NSIndexPath 0x84435f0> 2 indexes [0, 1], (
    "<CALayer: 0x8491010>"
)
2013-02-22 23:41:15.987 Clueless[3462:c07] <NSIndexPath 0x8446f50> 2 indexes [0, 2], (
    "<CALayer: 0x8495840>"
)
2013-02-22 23:41:26.161 Clueless[3462:c07] <NSIndexPath 0x827d970> 2 indexes [0, 12], (
    "<CALayer: 0x8241e20>"
)
2013-02-22 23:41:26.162 Clueless[3462:c07] <NSIndexPath 0x824e9d0> 2 indexes [0, 13], (
    "<CALayer: 0x827bc60>"
)
2013-02-22 23:41:26.163 Clueless[3462:c07] <NSIndexPath 0x827d030> 2 indexes [0, 14], (
    "<CALayer: 0x8242fb0>"
)
2013-02-22 23:41:26.776 Clueless[3462:c07] <NSIndexPath 0x82492e0> 2 indexes [0, 15], (
    "<CALayer: 0x8491010>"
)
2013-02-22 23:41:26.777 Clueless[3462:c07] <NSIndexPath 0x827f750> 2 indexes [0, 16], (
    "<CALayer: 0x8493ef0>"
)
2013-02-22 23:41:26.778 Clueless[3462:c07] <NSIndexPath 0x827f5c0> 2 indexes [0, 17], (
    "<CALayer: 0x8495840>"
)
2013-02-22 23:41:26.926 Clueless[3462:c07] <NSIndexPath 0x845cb90> 2 indexes [0, 0], (
    "<CALayer: 0x8495840>"
)
2013-02-22 23:41:26.927 Clueless[3462:c07] <NSIndexPath 0x84435f0> 2 indexes [0, 1], (
    "<CALayer: 0x8493ef0>"
)
2013-02-22 23:41:26.928 Clueless[3462:c07] <NSIndexPath 0x8446f50> 2 indexes [0, 2], (
    "<CALayer: 0x8491010>"
)

Answer 1

我不知道这是一个错误，还是我的问题。

但是，似乎要克服这个问题，您需要在 prepareForReuse 内强制 drawRect:

- (void)prepareForReuse
{
    [super prepareForReuse];

    [self setNeedsDisplay];
}