Question

我正在对UICollectionViewCell进行子类化，因为我想在单元格中添加UIImageView和UIProgressView：

- (id)initWithFrame:(CGRect)frame {

    self = [super initWithFrame:frame];
    if (self) {

        // ImageView
        _imageView = [[UIImageView alloc] initWithFrame:self.bounds];
        _imageView.layer.borderColor = [UIColor whiteColor].CGColor;
        _imageView.layer.borderWidth = 0.7;
        [self.contentView addSubview:_imageView];

        // Progress View
        _progressView = [[UIProgressView alloc] initWithProgressViewStyle:UIProgressViewStyleBar];
        _progressView.frame = CGRectMake(5, self.bounds.size.height - 20, self.bounds.size.width - 10, 10);
        _progressView.hidden = YES;
        [self.contentView addSubview:_progressView];

    }
    return self;
}

当我触摸一个单元格并调用collectionView:didSelectItemAtIndexPath:时，我设置cell.progressView.hidden = NO;并开始下载和更新progressView。

但是，当我滚动时，该单元格被重用，progressView显示在其他单元格上。我已经尝试了许多不同的东西，只能在正确的单元格上显示它，但我尝试过的任何东西都在工作。

有没有更好的方法来执行此操作，例如在prepareForReuse中执行某些操作？

编辑：请求的完整方法

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    PUCViewpointItem *item = [self.items objectAtIndex:indexPath.row];
    PUCImageGridCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:CollectionViewCellIdentifier forIndexPath:indexPath];
    [cell.imageView setImageWithURL:[NSURL URLWithString:item.imageURLHigh] placeholderImage:[UIImage imageNamed:@"PUCDefaultBackground.png"]];

    // See if we have the file already
    if (![self.itemPaths objectForKey:item.name]) {
        cell.imageView.alpha = 0.4;
    } else {
        cell.imageView.alpha = 1.0;
    }

    // See if we are downloading
    if (![self.progressItems objectForKey:item.name]) {
        cell.progressView.hidden = YES;
    } else {
        cell.progressView.hidden = NO;
    }

    return cell;
}


- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {

    PUCViewpointItem *item = [self.items objectAtIndex:indexPath.row];
    PUCImageGridCell *cell = (PUCImageGridCell *)[collectionView cellForItemAtIndexPath:indexPath];

    // File Path
    NSString *path = [self itemPath:item];
    if (!path) {

        // Set the indexPath we are downloading
        [self.progressItems setObject:indexPath forKey:item.name];

        Utility *utility = [[Utility alloc] init];
        NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:item.url]];
        AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];

        NSString *localPath = [[utility localDirectory] stringByAppendingFormat:@"/%@.pdf", item.name];
        operation.outputStream = [NSOutputStream outputStreamToFileAtPath:localPath append:NO];

        [operation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead) {

            float totalProgress = (float)totalBytesRead/(float)totalBytesExpectedToRead;
            if ([[collectionView indexPathForCell:cell] isEqual:indexPath]) {
                cell.progressView.alpha = 1.0;
                cell.progressView.progress = totalProgress;
            }

        }];
        [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {

            // This section seems to not get called or updated correctly when the cell 
            // that is showing the activityView is offscreen
            if ([[collectionView indexPathForCell:cell] isEqual:indexPath]) {
                [self.itemPaths setObject:localPath forKey:item.name];
                [self.progressItems removeObjectForKey:item.name];
                cell.imageView.alpha = 1.0;
                cell.progressView.alpha = 0.0;
            }

        } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
            NSLog(@"Error: %@", error);
            [self.progressItems removeObjectForKey:item.name];
            cell.progressView.alpha = 0.0;
        }];

        [operation start];

    } else {

        [self readIssueAtPath:path];

    }

}//end

Answer 1

应存储是否正在为某个项目进行下载的信息在某些数据源（或模型）中而不在单元格中（视图）。

然后，您可以根据该索引处项目的状态更新数据源委托方法collectionView:cellForItemAtIndexPath:中的单元格外观路径并显示或隐藏单元格的进度视图。

已添加：进度，完成和失败块都捕获当前单元格。因此，即使它已被重用于不同的索引路径，它们也会修改此单元格。要解决此问题，您可以检查单元格（当前）索引路径是否仍然相等到原始（捕获）索引路径：

[operation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead) {

    float totalProgress = (float)totalBytesRead/(float)totalBytesExpectedToRead;
    if ([[collectionView indexPathForCell:cell] isEqual:indexPath]) {
       cell.progressView.alpha = 1.0;
       cell.progressView.progress = totalProgress;
    }
}];

和类似的完成和失败块：

[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
    [self.itemPaths setObject:localPath forKey:item.name];
    [self.progressItems removeObjectForKey:item.name];
    if ([[collectionView indexPathForCell:cell] isEqual:indexPath]) {
        cell.imageView.alpha = 1.0;
        cell.progressView.alpha = 0.0;
    }

} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    NSLog(@"Error: %@", error);
    [self.progressItems removeObjectForKey:item.name];
    if ([[collectionView indexPathForCell:cell] isEqual:indexPath]) {
        cell.progressView.alpha = 0.0;
    }
}];

Answer 2

我认为您需要做的只是在didSelectRowAtIndexPath方法的开头引用一次单元格，并创建一个属性来跟踪所选的indexPath和进度指示器的值。下面的方法有效，但我必须创建一个虚拟慢速方法来测试它，所以我希望你能看到如何使这个适应你的问题。

@interface TableController ()
@property (strong,nonatomic) NSArray *theData;
@property (strong,nonatomic) NSIndexPath *downloadingCellPath;
@property (nonatomic) float progValue;
@end

@implementation TableController

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    RDCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cell" forIndexPath:indexPath];
    cell.label.text = self.theData[indexPath.row];
    if ([self.downloadingCellPath isEqual:indexPath]) {
        cell.progView.hidden = NO;
    }else{
        cell.progView.hidden = YES;
    }
    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{

    self.downloadingCellPath = indexPath;
    [self.tableView reloadData];
    [self longMethod:indexPath];
}


-(void)longMethod:(NSIndexPath *) indexPath {
    UIProgressView *activeProgressView = [(RDCell *)[self.tableView cellForRowAtIndexPath:indexPath] progView];
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        float x = 0;
        for (int i=0; i < 40000000; i++) {
            x = i * 3.14;
        }

        dispatch_async(dispatch_get_main_queue(), ^{
            self.progValue +=.01;
            activeProgressView.progress = self.progValue;
            if (self.progValue < .99){
                [self longMethod:indexPath];
            }else{
                NSLog(@"done");
                self.downloadingCellPath = nil;
                [self.tableView reloadRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationNone];
            }
        });
    });
}

Answer 3

[operation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead) {

    float totalProgress = (float)totalBytesRead/(float)totalBytesExpectedToRead;
    if ([[collectionView indexPathForCell:cell] isEqual:indexPath]) {
       cell.progressView.alpha = 1.0;
       cell.progressView.progress = totalProgress;
    }
}];

使用UIProgressView的自定义UICollectionViewCell在重用的单元格上显示progressView

3 个答案: