[英]UICollectionview cell selection
我制作了一个图像网格,为了显示其选择,我在选择时为图像绘制了边框。 但问题是当我在顶部选择一些图像并向下滚动图像网格时,底部的其他一些图像似乎也被选中。 下面是我的代码片段:
UINib *cellNib = [UINib nibWithNibName:@"collectionCell" bundle:nil];
[self.collectionView registerNib:cellNib forCellWithReuseIdentifier:@"cellCV"];
UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
[flowLayout setItemSize:CGSizeMake(95, 95)];
[flowLayout setScrollDirection:UICollectionViewScrollDirectionVertical];
[self.collectionView setCollectionViewLayout:flowLayout];
上面已添加到viewDidLoad中,其中集合视图单元格设计为nib。
并实施以下代表:
-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
selectedImageIndex = indexPath.row;
[collectionView reloadData];
}
-(CollectionCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UIImage *img = [imageArray objectAtIndex:indexPath.row];
static NSString *cellIdentifier = @"cellCV";
CollectionCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:
cellIdentifier forIndexPath:indexPath];
cell.imageView.image = img;
cell.imageView.tag = indexPath.row;
UIImageView *imgView = (UIImageView *)[cell viewWithTag:indexPath.row];
if (indexPath.row == selectedImageIndex) {
imgView.layer.borderWidth = 4.0;
imgView.layer.borderColor = [UIColor redColor].CGColor;
NSLog(@"selected indexpath: %d", indexPath.row);
}
else {
imgView.layer.borderWidth = 0.0;
imgView.layer.borderColor = nil;
}
return cell;
}
我可以猜到重复使用单元格会出现问题,但不确定并且无法解决问题。 等待任何形式的帮助和建议。
提前致谢。
我不明白为什么会发生这种情况。 我不相信问题是使用row
与item
,虽然你真的应该使用item
。 但是,我可以想象,如果你的集合视图有多个section
,那么仅查看row
/ item
但忽略section
将是一个问题(即它将在每个 section
选择相同的item
编号)。
为了减少Gordian结,我建议保存所选项目的NSIndexPath
,然后使用它作为比较的基础。 这也使得在didSelectItemAtIndexPath
呈现优化变得容易。 无论如何,首先定义你的财产:
@property (nonatomic, strong) NSIndexPath *selectedItemIndexPath;
然后实现cellForItemAtIndexPath
和didSelectItemAtIndexPath
:
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *cellIdentifier = @"Cell";
CollectionCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];
cell.imageView.image = ...
if (self.selectedItemIndexPath != nil && [indexPath compare:self.selectedItemIndexPath] == NSOrderedSame) {
cell.imageView.layer.borderColor = [[UIColor redColor] CGColor];
cell.imageView.layer.borderWidth = 4.0;
} else {
cell.imageView.layer.borderColor = nil;
cell.imageView.layer.borderWidth = 0.0;
}
return cell;
}
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
// always reload the selected cell, so we will add the border to that cell
NSMutableArray *indexPaths = [NSMutableArray arrayWithObject:indexPath];
if (self.selectedItemIndexPath)
{
// if we had a previously selected cell
if ([indexPath compare:self.selectedItemIndexPath] == NSOrderedSame)
{
// if it's the same as the one we just tapped on, then we're unselecting it
self.selectedItemIndexPath = nil;
}
else
{
// if it's different, then add that old one to our list of cells to reload, and
// save the currently selected indexPath
[indexPaths addObject:self.selectedItemIndexPath];
self.selectedItemIndexPath = indexPath;
}
}
else
{
// else, we didn't have previously selected cell, so we only need to save this indexPath for future reference
self.selectedItemIndexPath = indexPath;
}
// and now only reload only the cells that need updating
[collectionView reloadItemsAtIndexPaths:indexPaths];
}
顺便说一句,请注意我并没有搞乱tag
属性(我认为没有价值)。 另请注意,我不是重新加载整个集合视图,而是仅重新加载所选单元格(如果还有一个先前选定的单元格,那也应该更高效)。
这段代码在Swift 3中:
if self.selectedItemIndexPath != nil && indexPath.compare(self.selectedItemIndexPath) == .orderedSame {
cell.imageView!.layer.borderColor = UIColor.red.cgColor
cell.imageView!.layer.borderWidth = 4.0
} else {
cell.imageView!.layer.borderColor = nil
cell.imageView!.layer.borderWidth = 0.0
}
return cell
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