滚动

Question

当我选择一个单元格时，它会变成蓝色，这很好。然后，当我向上滚动并且单元格不在视图中时，它会变回原始颜色。不知道如何解决这个问题。

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
    UICollectionViewCell *cell=[collectionView dequeueReusableCellWithReuseIdentifier:@"cellIdentifier" forIndexPath:indexPath];
    cell.backgroundColor=[UIColor lightGrayColor];
    [collectionView selectItemAtIndexPath:indexPath animated:NO scrollPosition:UICollectionViewScrollPositionNone];
    self.collectionView.allowsMultipleSelection=YES;

    return cell;
}

-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewCell *datasetCell =[collectionView cellForItemAtIndexPath:indexPath];
    datasetCell.backgroundColor = [UIColor blueColor];  
}

-(void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewCell *datasetCell =[collectionView cellForItemAtIndexPath:indexPath];  
}

Answer 1

重复使用单元格时，选择状态将丢失。因此，您需要在didSelectItemAtIndexPath中保存选择的indexPath。当您将单元格出列时，需要检查并恢复状态

Answer 2

在第一种方法中，您实际上是在告诉集合视图选择它要求的任何单元格。相反，你应该检查你返回的单元格是否与所选单元格具有相同的路径，然后才给它颜色：

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *cell=[collectionView dequeueReusableCellWithReuseIdentifier:@"cellIdentifier" forIndexPath:indexPath];
    if ([indexPath isEqual:self.selectedIndexPath]) // you need to create selectedIndexPath as a property
    {
        cell.backgroundColor=[UIColor blueColor];
    }
    else
    {
        cell.backgroundColor=[UIColor lightGrayColor];
    }
    return cell;
}

然后：

-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath 
{
    self.selectedIndexPath = indexPath;
}