Question

我正在将自定义单元格加载到 UICollectionView ，并且在每个 CELL1 上我有一个下载按钮和进度视图，但是当我开始时点击cell1按钮后下载的东西。我开始下载了我正在更新进度视图，显示正确的结果。但是当进度视图开启时（正在进行下载），当我向下滚动时，我看到 CELL5上的进度视图，再次如果我通过上下滚动来玩它我能够在 CELL6 看到进度视图......我在这里做错了什么？...

我的代码在这里：

- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath { MyCell *cell = (MyCell*)[cv dequeueReusableCellWithReuseIdentifier:@"MyCell" forIndexPath:indexPath]; cell.labelTitle.text = [_editionNameArray objectAtIndex:indexPath.row]; cell.labelIssue.text = [[[_editionDescriptionArray objectAtIndex:indexPath.row] stringByReplacingOccurrencesOfString:@"+" withString:@" "] stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding]; cell.issueButton.tag=indexPath.row; [cell.issueButton setTitle:@"Download" forState:UIControlStateNormal];//once the download is completed set the title as Read. [cell.issueButton addTarget:self action:@selector(downloadTheIssue:) forControlEvents:UIControlEventTouchUpInside]; cell.tag=indexPath.row; }

收到数据后，我正在更新进度视图，

- (void)downloadManager:(DownloadManager *)downloadManager downloadDidReceiveData:(Download *)download { [self updateProgressViewForIndexPath:[NSIndexPath indexPathForRow:download.tag inSection:0] download:download]; } - (void)updateProgressViewForIndexPath:(NSIndexPath *)indexPath download:(Download *)download { MyCell *cell = (MyCell *)[self.collectionView cellForItemAtIndexPath:indexPath]; // if the cell is not visible, we can return if (!cell) return; cell.progressView.hidden=NO; 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; } }

更新：

#import "MyCell.h" @implementation MyCell - (void)layoutSubviews { [super layoutSubviews]; self.backgroundView=[[UIImageView alloc]initWithImage:[UIImage imageNamed:@"gridbg.png"]]; self.labelTitle.textColor = [UIColor colorWithRed:0.18f green:0.20f blue:0.23f alpha:1.00f]; self.labelTitle.backgroundColor = [UIColor clearColor]; self.labelIssue.textColor = [UIColor colorWithRed:1.00f green:0.25f blue:0.55f alpha:1.00f]; self.labelIssue.backgroundColor = [UIColor clearColor]; }

非常感谢任何解决方案......

Answer 1

实际上你应该在某个地方存储每个项目的进度，因为当重用单元格时，它将会丢失并且永远不会恢复。例如，为此设置NSMutableArray *_downloadProgressArray并相应地调整您的方法：

- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    MyCell *cell = (MyCell*)[cv dequeueReusableCellWithReuseIdentifier:@"MyCell" forIndexPath:indexPath];

    cell.labelTitle.text = [_editionNameArray objectAtIndex:indexPath.row];
    cell.labelIssue.text = [[[_editionDescriptionArray objectAtIndex:indexPath.row]
                         stringByReplacingOccurrencesOfString:@"+" withString:@" "]
                        stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

    NSNumber* progress = [_downloadProgressArray objectAtIndex:indexPath.row];
    if (progress == nil) {
        // download not started
        cell.issueButton.hidden = NO;
        cell.issueButton.tag = indexPath.row;
        [cell.issueButton setTitle:@"Download" forState:UIControlStateNormal]; //once the download is completed set the title as Read.
        [cell.issueButton addTarget:self action:@selector(downloadTheIssue:) forControlEvents:UIControlEventTouchUpInside];
        cell.progressView.hidden = YES;
    } else {
        cell.issueButton.hidden = YES;
        cell.progressView.hidden = NO;
        cell.progressView.progress = progress.doubleValue;
    }

    cell.tag = indexPath.row;
    return cell;
}


- (void)downloadManager:(DownloadManager *)downloadManager downloadDidReceiveData:(Download *)download
{
    _downloadProgressArray[download.tag] = [NSNumber numberWithDouble:(your progress here)];
    [self updateProgressViewForIndexPath:[NSIndexPath indexPathForRow:download.tag inSection:0] download:download];
}

下载完成后不要忘记设置nil。

Answer 2

如您所说，您正在重复使用单元格，然后您必须将值重置为默认值，因为进度条值已更改，并且单元格在其他位置重复使用。

- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath
MyCell *cell = (MyCell*)[cv dequeueReusableCellWithReuseIdentifier:@"MyCell" forIndexPath:indexPath];
cell.progressView.progress = 0;
....

其他标签正在获取更新的值cell.labelIssue.text，因此除了progressView值之外没问题。

UICollectionView与重用单元格和滚动有关

2 个答案: