我正在构建一个应用程序，允许用户下载和阅读期刊的问题。我正在使用Download Manager framework created by Robert Ryan，我修改了框架附带的测试项目，使其在我的项目中工作（框架没有问题）。在表格的每一行上都有一个问题封面图像（UIImageView），下载/读取标签（UILabel），发行日期标签（UILabel）和进度条（UIProgressView）都是UITableViewCell的属性。当用户点击该行时，它会启动问题的下载过程，该过程会反映在进度条中;下载完成后，进度条将变为隐藏状态，标签的下载标题将更改为“读取”，当用户再次点击该行以读取下载的日志时，将在viewcontroller中打开PDF查看器。我还没有添加Read功能。所有这一切都很好，除了作为一个测试，我在表格中有两期日记与``。当我点击第一行时，进度条反映了下载进度，它工作正常。但是，当我点击第二行时，下载进度将反映在第一行的进度条中而不是第二行中的预期中（进度条保持静态）。它确实下载了第二个期刊，一切正常。只是这种意外行为，第二行的下载进度反映在第一行的进度条中。我仍然需要简化代码并清理它，但相关的代码部分如下：
// optional method to indicate progress of individual download
//
// In this view controller, I'll update progress indicator for the download.
- (void)downloadManager:(DownloadManager *)downloadManager downloadDidReceiveData: (Download *)download;
{
for (NSInteger row = 0; row < [downloadManager.downloads count]; row++)
{
if (download == downloadManager.downloads[row])
{
[self updateProgressViewForIndexPath:[NSIndexPath indexPathForRow:row inSection:0] download:download];
break;
}
}
}
#pragma mark - Table View delegate and data source methods
// our table view will simply display a list of files being downloaded
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return[jitsArray count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"DownloadCell";
DownloadCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[DownloadCell alloc]
initWithStyle:UITableViewCellStyleDefault
reuseIdentifier:CellIdentifier];
}
jits * jitsInstance = nil;
jitsInstance = [jitsArray objectAtIndex:indexPath.row];
cell.issue.text = jitsInstance.issue;
NSString * myCoverURL = [NSString stringWithFormat:@"%@", jitsInstance.coverimage];
UIImage* myImage = [UIImage imageWithData:
[NSData dataWithContentsOfURL:
[NSURL URLWithString: myCoverURL]]];
cell.coverimage.image = myImage;
[cell.progressView setProgress:0];
NSString * myURL = [NSString stringWithFormat:@"%@", jitsInstance.url];
NSString* documentsPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString *downloadFolder = [documentsPath stringByAppendingPathComponent:@"downloads"];
NSString * fileName = [[NSString alloc]initWithFormat:@"%@", [myURL lastPathComponent]];
NSString* foofile = [downloadFolder stringByAppendingPathComponent:fileName];
BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:foofile];
NSLog(@"Search file path: %@", foofile);
if (!fileExists) {
[cell.downloadButton setTitle:@"Download" forState:normal];
[cell.progressView setHidden:NO];
NSLog(@"File does not exist!");
}
else if (fileExists){
NSLog(@"File exist!");
[cell.downloadButton setTitle:@"Read" forState:normal];
[cell.progressView setHidden:YES];
}
return cell;
}
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
[tableView deselectRowAtIndexPath:indexPath animated:YES];
NSString *documentsPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
NSString *downloadFolder = [documentsPath stringByAppendingPathComponent:@"downloads"];
jits * jitsInstance = nil;
jitsInstance = [jitsArray objectAtIndex:indexPath.row];
NSString * myURL = [NSString stringWithFormat:@"%@", jitsInstance.url];
self.downloadManager = [[DownloadManager alloc] initWithDelegate:self];
self.downloadManager.maxConcurrentDownloads = 4;
NSString *downloadFilename = [downloadFolder stringByAppendingPathComponent:[myURL lastPathComponent]];
NSURL *url = [NSURL URLWithString:myURL];
[self.downloadManager addDownloadWithFilename:downloadFilename URL:url];
self.cancelButton.enabled = YES;
self.startDate = [NSDate date];
[self.downloadManager start];
}
#pragma mark - Table view utility methods
- (void)updateProgressViewForIndexPath:(NSIndexPath *)indexPath download:(Download *)download
{
DownloadCell *cell = (DownloadCell *)[self.tableView cellForRowAtIndexPath: [NSIndexPath indexPathForRow:indexPath.row inSection:0]];
// if the cell is not visible, we can return
if (!cell)
return;
if (download.expectedContentLength >= 0)
{
// if the server was able to tell us the length of the file, then update progress view appropriately
// to reflect what % of the file has been downloaded
cell.progressView.progress = (double) download.progressContentLength / (double) download.expectedContentLength;
}
else
{
// if the server was unable to tell us the length of the file, we'll change the progress view, but
// it will just spin around and around, not really telling us the progress of the complete download,
// but at least we get some progress update as bytes are downloaded.
//
// This progress view will just be what % of the current megabyte has been downloaded
cell.progressView.progress = (double) (download.progressContentLength % 1000000L) / 1000000.0;
}
}
答案 0 :(得分：0)
我认为您的问题可能在于以下代码：
for (NSInteger row = 0; row < [downloadManager.downloads count]; row++)
{
if (download == downloadManager.downloads[row])
{
[self updateProgressViewForIndexPath:[NSIndexPath indexPathForRow:row inSection:0] download:download];
break;
}
}
这看起来基本上就是在下载数组中找到第一个单元格，在找到的第一个单元格上调用updateProgressViewForIndexPath，然后停止。有很多方法可以解决这个问题，但首先想到的是，当if语句的计算结果为true时，告诉自己更新该索引路径的单元格，从downloadManager的下载数组中删除该项目，下次通过它不会在那里。尝试一下，让我知道这是否有效..
另外，在旁注中......我认为每次选择一行时你都不想做以下两行：
self.downloadManager = [[DownloadManager alloc] initWithDelegate:self];
self.downloadManager.maxConcurrentDownloads = 4;
在我看来，这可能是你想要在tableView的init方法中做的事情所以它只发生一次，而不是每次用户点击一行。也许你每次尝试创建一个新的下载管理器并将其设置为属性？这对我来说似乎不正统。如果我有权访问该项目，我想我可能会更好地帮助调试。如果我的回复没有帮助，您是否有机会分享项目？