iphone - 我的 ImageView 在 TableView 中表现不正常？

Question

我有一个以下面的方式加载的表格 View 。如果满足条件，我需要在 cell.imageview 上方添加特定图像。这些图像也有不同的尺寸。下面是我的代码，任何人都可以指出我哪里出错了。

static NSString *CellIdentifier = @"Cell";

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
}
if(array==nil||[array count]==0)
{

}
else
{
    NSMutableDictionary *dicttable=[array objectAtIndex:indexPath.row];
    NSString *head=[dicttable objectForKey:@"name"];
    NSString *type=[dicttable objectForKey:@"type"];

    NSString *imgUrl = [dicttable objectForKey:@"image"];;
    if(imgUrl!=nil)
    {
        if(![[ImageCache sharedImageCache] hasImageWithKey:imgUrl])
        { 
            cell.imageView.image = [UIImage imageNamed:@"noimage_icon.png"];
            NSArray *myArray = [NSArray arrayWithObjects:cell.imageView,imgUrl,@"noimage_icon.png",[NSNumber numberWithBool:NO],nil];
            AppDelegate *appDelegate = (AppDelegate  *)[[UIApplication sharedApplication] delegate];
            [appDelegate performSelectorInBackground:@selector(updateImageViewInBackground:) withObject:myArray];
            cell.imageView.frame=CGRectMake(0,0,48,48);
            cell.imageView.bounds=CGRectMake(0,0,48,48);
            [cell.imageView setClipsToBounds:NO];
        }
        else
        {
            cell.imageView.image = [[ImageCache sharedImageCache] getImagefromCacheOrUrl:imgUrl];
            cell.imageView.frame=CGRectMake(0,0,48,48);
            cell.imageView.bounds=CGRectMake(0,0,48,48);
            [cell.imageView setClipsToBounds:NO];
        }
    }
    else
    {
        cell.imageView.image = [UIImage imageNamed:@"noimage_icon.png"];
    }
    if([type isEqualToString:@"YES"])
    {
        UIImageView* img = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"bluel.png"]];
        [cell setBackgroundView:img];
        [img release];

        cell.textLabel.text = head;
        cell.textLabel.backgroundColor = [UIColor clearColor];

        cell.detailTextLabel.textColor=[UIColor grayColor];
        cell.detailTextLabel.text = subtitle1;
        cell.detailTextLabel.backgroundColor = [UIColor clearColor];
    }
    else
    {
        UIImageView* img = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"wnew1.png"]];
        [cell setBackgroundView:img];
        [img release];
        cell.textLabel.text = head;
        cell.textLabel.backgroundColor = [UIColor clearColor];
        [cell.imageView addsubview:spclimage]

        cell.textLabel.text = head;
        cell.textLabel.backgroundColor = [UIColor clearColor];

        cell.detailTextLabel.textColor=[UIColor grayColor];
        cell.detailTextLabel.text = subtitle1;
        cell.detailTextLabel.backgroundColor = [UIColor clearColor];            
    }
}
return cell;

这里的问题仅在于添加特殊图像的最后一行。并非在所有行中。另外，在重新加载表格 View 的过程中， ImageView 的大小也有所不同？

Answer 1

一些想法:

1. updateImageViewInBackground 似乎很可疑，顾名思义，您正在更新 ImageView ，但您没有指定要更新哪个单元格。

   <

2. 我还看到您在执行 addSubview:spclimage。显然，如果该 spclimage 位于另一个单元格上，那么一旦您执行 addSubview ，它将在添加到当前单元格之前从之前的位置删除。事实上，将图像添加为现有 ImageView 的 subview 的想法就很奇怪。

3. 如果您的缓存还没有图像，我会看到您使用 noimage_icon.png 初始化图像的位置，但看不到您实际更新的位置 ImageView 。你说 updateImageViewInBackground 是“然后更新图像”。您的意思是为此 indexPath 设置此 cell 的 imageView 的 image 属性吗？或者也许更新spclimage？如果是这样，那就有问题了。

4. 典型的模式(使用 GCD)是:

   cell.imageView.image = [UIImage imageNamed:@"noimage_icon.png"];
   
   dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
       UIImage *image = ... // do whatever you need to do to get the image, load cache, etc.
   
       // ok, now that you have the image, dispatch the update of the UI back to the main queue
   
       dispatch_async(dispatch_get_main_queue(), ^{
   
           // because we're doing this asynchronously, make sure the cell is still
           // visible (it could have scrolled off and the cell was dequeued and
           // reused), so we're going to ask the tableview for the cell for that
           // indexPath, and it returns `nil` if it's not visible. This method is
           // not to be confused with the similarly named `UITableViewControllerDelegate`
           // method.
   
           UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
   
           // if the image view is still visible, update it
   
           if (cell)
           {
               cell.imageView.image = image;
           }    
       });
   
   });