Question

当我下载文件时，我正在尝试更新UICollectionViewCell中的UIProgressView，但有时progressView更新并且有时不更新，我无法理解为什么，这是显示UICollectionViewCell的代码：

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {

static NSString *cellIdentifier = @"documentCell";

UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];

NSManagedObject *doc = [self.magDocument objectAtIndex:indexPath.row];

 UIButton *btn = (UIButton *)[cell viewWithTag:2003];
[btn addTarget:self action:@selector(addDocument:) forControlEvents:UIControlEventTouchUpInside];
UIProgressView *progressBar = (UIProgressView *)[cell viewWithTag:2005];

return cell;
}

这是开始下载的按钮：

- (IBAction)addDocument:(id)sender
{
self.directCellPath = [self.myCollectionView indexPathForCell:(UICollectionViewCell *)[[sender superview] superview]];

NSManagedObject *document = [self.magDocument objectAtIndex:self.directCellPath.row];

[self loadLink:[document valueForKey:@"docUrl"]];
}

- (void)loadLink:(NSString *)urlDownload
{
UICollectionViewCell *cell = (UICollectionViewCell *)[self.myCollectionView cellForItemAtIndexPath:self.directCellPath];
UIProgressView *prg = (UIProgressView *)[cell viewWithTag:2005];

AFDownloadRequestOperation *request = [[AFDownloadRequestOperation alloc] initWithRequest:requestUrl targetPath:zipDownloadPath shouldResume:YES];

    [request setProgressiveDownloadProgressBlock:^(NSInteger bytesRead, long long totalBytesRead, long long totalBytesExpected, long long totalBytesReadForFile, long long totalBytesExpectedToReadForFile) {

            NSLog(@"%f",totalBytesReadForFile/(float)totalBytesExpectedToReadForFile);
        NSArray *progress = [NSArray arrayWithObjects:prg,[NSNumber numberWithFloat:totalBytesReadForFile/(float)totalBytesExpectedToReadForFile], nil];

        [self performSelectorOnMainThread:@selector(updateProgressBar:) withObject:progress waitUntilDone:NO];
    }];

    [self.downloadQueue addOperation:request];
 }

- (void)updateProgressBar:(NSArray *)progress
{
UIProgressView *pgr = (UIProgressView *)[progress objectAtIndex:0];
[pgr setProgress:[[progress objectAtIndex:1] floatValue]];
}

一次进度视图有效，而其他一千次无效，我无法理解如何更新进度视图，有什么帮助吗？

Answer 1

创建customCell并在其中显示所有可见的UIViews（init，add subview ...）。比使用cellForItemAtIndexPath中的自定义方法来激活（显示）它。如果你考虑MVC，cellForItemAtIndexPath只适用于Controller，而不是View。

在您的情况下，将所有IBAction，loadLink和updateProgress带到customCell并发送参数以激活它们，或者您可以创建新协议，如CustomCellDelegate进行通信。

检查更多信息：

Error setting text in collection view cell

Answer 2

可能是关于线程问题。试试

dispatch_async(dispatch_get_main_queue(), ^{
            UIProgressView *pgr = (UIProgressView *)[progress objectAtIndex:0];
            [pgr setProgress:[[progress objectAtIndex:1] floatValue]];
       });//end block

尝试异步或同步

在UICollectionViewCell中更新UIProgressView以获取下载文件

2 个答案: