ios - 单击 UIButton 时 UITableView 卡住

Question

我在实现 UITableView 时遇到问题，其中每个单元格都有一个 UIImageView、UILabel。我正在使用延迟加载，因为数据是使用 JSON 从 Web 服务检索的。

我有一个按钮需要删除一个 subview (比如 UIView)并调整 TableView 的大小。

我的问题是，当我单击按钮时，UITableView 的滚动变得非常缓慢。当我分析我的应用程序时，它显示 UITableView 中的 UIImageView 存在泄漏。

这是我在 UITableView 中的代码，

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

     static NSString *cellId = @"Cell";
     UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellId];

     UIActivityIndicatorView *activityIndicator =  [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
     activityIndicator.color = [UIColor blueColor];

     if (cell == nil){
         cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:nil];
         cell.selectionStyle = UITableViewCellSelectionStyleBlue;

         if (lblTitle==nil){
             lblTitle =[[UILabel alloc]init];
         }
         if (thumbnailImage==nil){
             thumbnailImage = [[UIImageView alloc]init];
         }
     }

     [cell addSubview:lblTitle];
     [cell addSubview:thumbnailImage];

// set frames for table view cell
     if ([[UIDevice currentDevice]userInterfaceIdiom]==UIUserInterfaceIdiomPhone){

         lblTitle.frame = CGRectMake(110, 0, 210, 100);
         thumbnailImage.frame = CGRectMake(5, 5, 100, 90);
         activityIndicator.frame = CGRectMake(40, 30, 35, 35);
         lblTitle.font = [UIFont fontWithName:@"Papyrus" size:16.0f];
     }else{

         lblTitle.frame = CGRectMake(215, 0, 590, 150);
         lblTitle.font = [UIFont fontWithName:@"Papyrus" size:25.0f];
         thumbnailImage.frame = CGRectMake(5, 5, 200, 140);
         activityIndicator.frame = CGRectMake(85, 45, 75, 75);
     }

     lblTitle.numberOfLines = 2;
     lblTitle.textColor = [UIColor colorWithRed:105/255.0f green:205/255.0f blue:220/255.0f alpha:1.0f];
     lblTitle.backgroundColor = [UIColor clearColor];

     thumbnailImage.tag = indexPath.row;

     // display data
     lblTitle.text = [[rssNewsArray objectAtIndex:indexPath.row] objectForKey:@"title"];

     //lazy loding of images
     DataContainer *currentContainer;

     if (profImageDataContainer.count!=0)
         currentContainer= [profImageDataContainer objectAtIndex:indexPath.row];

     if(currentContainer.cellImage)
         thumbnailImage.image = currentContainer.cellImage;
     else{
         //checking whether thumbnail is null
         if (![[[rssNewsArray objectAtIndex:indexPath.row] objectForKey:@"image"] isKindOfClass:[UIImage class]])
         {

             if ([self checkNetworkStatus:nil]){

                 if(![[[rssNewsArray objectAtIndex:indexPath.row] objectForKey:@"thumbnail"] isEqualToString:@""] && ([[[rssNewsArray objectAtIndex:indexPath.row] objectForKey:@"thumbnail"] rangeOfString:@".jpg"].location!=NSNotFound || [[[rssNewsArray objectAtIndex:indexPath.row] objectForKey:@"thumbnail"] rangeOfString:@".jpeg"].location!=NSNotFound || [[[rssNewsArray objectAtIndex:indexPath.row] objectForKey:@"thumbnail"] rangeOfString:@".png"].location!=NSNotFound))
                 {

                     activityIndicator.tag = indexPath.row;

                     // Start it animating and add it to the view
                     [activityIndicator startAnimating];
                     [cell addSubview:activityIndicator];
                     NSString *urlstr = [[rssNewsArray objectAtIndex:indexPath.row] objectForKey:@"thumbnail"];
                     urlstr = [urlstr stringByReplacingOccurrencesOfString:@" " withString:@"%20"];

                     NSURL *imgURL = [NSURL URLWithString:urlstr];

                     thumbnailImage.image=[UIImage imageNamed:@"albumsPlaceHolder.png"];

                     NSMutableArray *array = [[NSMutableArray alloc]initWithObjects:imgURL,[NSString stringWithFormat:@"%d", indexPath.row],activityIndicator,thumbnailImage, nil];

                     [self performSelectorInBackground:@selector(loadImageInBackground:) withObject:array];

                 }else
                 {
                     thumbnailImage.image=[UIImage imageNamed:@"albumsPlaceHolder.png"];
                 }
             }
             else
             {
                 thumbnailImage.image=[UIImage imageNamed:@"albumsPlaceHolder.png"];
             }
         }
         else
         {
             thumbnailImage.image=[[rssNewsArray objectAtIndex:indexPath.row] objectForKey:@"image"];

         }
      }
         thumbnailImage=nil;
         lblTitle=nil;
         activityIndicator=nil;
         return cell;
 }

和按钮操作

- (IBAction)actCloseTicker:(id)sender
{

    [self.ticker pause];
    self.ticker=nil;
    NSUserDefaults *def = [NSUserDefaults standardUserDefaults];
    [def setBool:NO forKey:@"ticker"];
    [def synchronize];
    def=nil;

    [self.tickerView removeFromSuperview];

    if ([[UIDevice currentDevice]userInterfaceIdiom]==UIUserInterfaceIdiomPhone)
    {
        self.tblRSSNews.frame = CGRectMake(0, 0, 320, self.view.frame.size.height);
    }
    else
    {
        self.tblRSSNews.frame = CGRectMake(0, 0, 768, self.view.frame.size.height);
    }
    }

提前致谢。

Answer 1

根据发布的代码，您的 tableView 没有重用创建的单元格，因为您正在使用 reuseIdentifier:nil 分配单元格，这意味着每次需要显示新单元格时，它都会分配一个新的单元格并添加新的标签和 imageView 实例，这可能会导致速度变慢。您可以尝试更改如下代码:

UILabel *lblTitle = nil;
UIImageView *thumbnailImage = nil;
if (cell == nil){
     cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellId ];
     cell.selectionStyle = UITableViewCellSelectionStyleBlue;

     if (lblTitle==nil){
         lblTitle =[[UILabel alloc]init];
         lblTitle.tag = 1000;
     }
     if (thumbnailImage==nil){
         thumbnailImage = [[UIImageView alloc]init];
         thumbnailImage.tag = 1001;
     }
      [cell addSubview:lblTitle];
      [cell addSubview:thumbnailImage];
 }
 else{
     lblTitle = (UILabel*)[cell viewWithTag:1000];
     thumbnailImage = (UIImageView*)[cell viewWithTag:1001];
 }