子类 UICollectionViewCell 不更新图像

Question

我正在尝试通过在每个单元格视图中添加一个徽章来使集合视图显示多个选择。它正确设置了初始（未选择）图像，但视图永远不会更新到所选版本。我已经尝试手动设置它，所以我知道所选图像有效并且在单元格中可见。 NSLog 显示“已选择”正在按预期切换，断点显示正在执行对图像的适当分配。对不起，缩进，所以不会很好玩，而且是在午夜之后。

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    SMListCollectionViewCell *cell = (SMListCollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];

if ( !indexPath.row )
{
    cell.image.image = [UIImage imageNamed:@"Add"];
    cell.label.text = @"Create New";
    cell.imageBadge.hidden = YES;
}
else
{
    cell.image.image = [UIImage imageNamed:[listManager.myLists[indexPath.row-1] valueForKey:keyDetailImage]];
    cell.label.text = [listManager.myLists[indexPath.row-1] valueForKey:keyName];
    cell.imageBadge.hidden = !self.editing;
    NSLog(@"selected is %d",cell.selected);
    if ( cell.selected )
    {
        cell.imageBadge.image = self.badgeSelected;
    }
    else
    {
        cell.imageBadge.image = self.badgeUnselected;
    }
}
return cell;
}

Answer 1

哇！从cellForAtIndexPath: 中检查cell 的selected 状态保证不会工作。

由于您已经创建了一个自定义单元格子类SMListCollectionViewCell，您需要覆盖其selected 设置器并从那里切换要在单元格上显示的图像。

由于imageBadge 属性已经在SMListCollectionViewCell.h 中公开，因此只有.m 的快速sn-p 看起来像：

// SMListCollectionViewCell.m

#import "SMListCollectionViewCell.h"

@implementation SMListCollectionViewCell

... 

- (void)setSelected:(BOOL)selected{
    [super setSelected:selected];

    if (selected){
        cell.imageBadge.image = self.badgeSelected;
    }
    else {
        cell.imageBadge.image = self.badgeUnselected;
    }
}

@end

?? 这将根据单元格选择状态处理图像切换。

此外，cellForItemAtIndexPath: 现在将变形为：

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    SMListCollectionViewCell *cell = (SMListCollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];

    if (!indexPath.row){

        cell.image.image = [UIImage imageNamed:@"Add"];
        cell.label.text = @"Create New";
        cell.imageBadge.hidden = YES;
    }
    else {

        cell.image.image = [UIImage imageNamed:[listManager.myLists[indexPath.row-1] valueForKey:keyDetailImage]];
        cell.label.text = [listManager.myLists[indexPath.row-1] valueForKey:keyName];
        cell.imageBadge.hidden = !self.editing;
    }

    return cell;
}