由于可重用性问题，tableview 单元格上的图像重复

Posted 2023-03-12

【中文标题】由于可重用性问题，tableview 单元格上的图像重复

【英文标题】：image on tableview cell repeating due to reusability issue

【发布时间】：2016-03-28 09:33:45

【问题描述】：

我有一个表格视图单元格，有标签和图像，在滚动图像和标签时发生变化，这是由于单元格出列功能。我试图通过将 imageview 设置为 nil 来解决它，但它没有工作。 重复的问题在于 PinImageView，它从一组图像中获取图像，而不是从 URL 中获取图像。

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

    static NSString *cellIdentifier=@"cellIdentifier";
    TripInfoListCell *cell=[tableView dequeueReusableCellWithIdentifier:cellIdentifier];

    if (cell==nil) 
        cell=(TripInfoListCell *)[[[NSBundle mainBundle] loadNibNamed:@"TripInfoListCell" owner:self options:nil] firstObject];

    

   cell.PinImageView.image = nil;


    NSString *direction=[dict123 valueForKey:@"direction" ] ;
    NSString *drive_status=[dict123 valueForKey:@"driver_or_rider"];

    if((indexPath.row==totalRow-1)&&[direction isEqual:@"From"])
    
        __weak TripInfoListCell *weakCell = cell;

        cell.PinImageView.image=[UIImage imageNamed:@"[e-mail]"];
       cell.userNameLabel.text=loggedUser.profile_name;

        cell.riderDriverSlNo.text=@"Driver";

        if([drive_status  isEqual:@"Ride"])

       
           cell.riderDriverSlNo.text=@"Driver";
            cell.userNameLabel.text=@"Driver"; //In case of "Rider" "From" name in the last row
                  
        else
        cell.availabiltyInfoLabel.text=@"You";
        

        NSString *imagePic = [[NSUserDefaults standardUserDefaults] objectForKey:@"user_image"];
    NSURLRequest *request=[NSURLRequest requestWithURL:[NSURL URLWithString:imagePic]];

        [cell.userImageView setImageWithURLRequest:request placeholderImage:nil success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) 

            weakCell.userImageView.image=image;

         failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) 

            NSLog(@"%@",error);
        ];


    
    else if((indexPath.row==totalRow-1)&&[direction isEqual:@"To"])

    
        cell.PinImageView.image=[UIImage imageNamed:@"[e-mail]"];
        cell.userNameLabel.text=[_tripDetails objectForKey:@"park_name"];

        NSString *image=[NSString stringWithFormat:@"%@",[dict123 objectForKey:@"parkBannerImageUrl"]];

        [[ImageHandler sharedInstance] getImageFromURL:image withCompletion:^(UIImage *image) 

            if (image) 

                [cell.userImageView setImage:image];
            
        ];
    
    else
      if ([tableGoersList count] > indexPath.row)
        

             NSDictionary *goersInfo=[tableGoersList objectAtIndex:indexPath.row];

        [[NSUserDefaults standardUserDefaults]setObject:[goersInfo valueForKey:@"user_image_url"] forKey:@"user_image"];
        [[NSUserDefaults standardUserDefaults]synchronize];

        __weak TripInfoListCell *weakCell = cell;

        NSURLRequest *request=[NSURLRequest requestWithURL:[NSURL URLWithString:goersInfo[@"user_image_url"]]];

        [cell.userImageView setImageWithURLRequest:request placeholderImage:nil success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) 

            weakCell.userImageView.image=image;

         failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) 

            NSLog(@"%@",error);
        ];

        if((indexPath.row==0)&&[direction isEqual:@"To"]) 

            if([drive_status  isEqual:@"Drive"])

            cell.riderDriverSlNo.text=@"Driver";


            cell.PinImageView.image=[UIImage imageNamed:@"[e-mail]"];
            cell.userNameLabel.text=loggedUser.profile_name;
             cell.availabiltyInfoLabel.text=@"You";
            
            else
            
        
        else if((indexPath.row==0)&&[direction isEqual:@"From"]) 

            if([drive_status  isEqual:@"Drive"])
            

            cell.PinImageView.image=[UIImage imageNamed:@"[e-mail]"];
            cell.userNameLabel.text=[_tripDetails objectForKey:@"park_name"];
            cell.riderDriverSlNo.text=@"";
            cell.availabiltyInfoLabel.text=@"";

            NSString *image=[NSString stringWithFormat:@"%@",[dict123 objectForKey:@"parkBannerImageUrl"]];

            [[ImageHandler sharedInstance] getImageFromURL:image withCompletion:^(UIImage *image) 

                if (image) 

                    [cell.userImageView setImage:image];
                
            ];
            
            else
                NSLog(@"rider from");
                cell.riderDriverSlNo.text=@"";

            

        
        else

            imageNameArray = [[NSArray alloc] initWithObjects:@"[e-mail]", @"[e-mail]", @"[e-mail]", @"[e-mail]", @"[e-mail]",@"[e-mail]",@"[e-mail]", nil];

            NSString* nameStr=[goersInfo valueForKey:@"name"];

           NSArray * nameStrArray = [nameStr componentsSeparatedByString: @"'s"];
            nameStr=[nameStrArray objectAtIndex:0];
            cell.riderDriverSlNo.text=[NSString stringWithFormat:@"Rider %ld",(long)indexPath.row];

            index = [TripInfoVC ifNameExists:_arrName Name:nameStr];

            if(index == 0)
            
                cell.PinImageView.image=[UIImage imageNamed:[imageNameArray objectAtIndex:0]];
                 [_arrName addObject:nameStr];

            
            if(index == 1)
            
                cell.PinImageView.image=[UIImage imageNamed:[imageNameArray objectAtIndex:1]];
            
            if(index == 2)
            
                cell.PinImageView.image=[UIImage imageNamed:[imageNameArray objectAtIndex:2]];
            

            if(index == 3)
            
                cell.PinImageView.image=[UIImage imageNamed:[imageNameArray objectAtIndex:3]];
            


            if(index == 4)
            
                cell.PinImageView.image=[UIImage imageNamed:[imageNameArray objectAtIndex:4]];
            

            if(index == 5)
            
            cell.PinImageView.image=[UIImage imageNamed:[imageNameArray objectAtIndex:5]];
            

            if(index == 6)
            
            cell.PinImageView.image=[UIImage imageNamed:[imageNameArray objectAtIndex:6]];
            

            if(index == 7)
            
            cell.PinImageView.image=[UIImage imageNamed:[imageNameArray objectAtIndex:0]];
            

            if(index == 8)
            
           cell.PinImageView.image=[UIImage imageNamed:[imageNameArray objectAtIndex:1]];
            

            if(index == 9)
            
           cell.PinImageView.image=[UIImage imageNamed:[imageNameArray objectAtIndex:2]];
            

            if(index == 10)
            
            cell.PinImageView.image=[UIImage imageNamed:[imageNameArray objectAtIndex:3]];
            

          // this pinImageView is the pin image which is repeated on scrolling

    return cell;

请帮我解决这个问题。

【参考方案1】：

你可能会面临关闭碰撞。当你声明完成块时

[cell.userImageView setImageWithURLRequest:request placeholderImage:nil success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) 

            weakCell.userImageView.image=image;

         failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) 

            NSLog(@"%@",error);
        ];

weakCell 是指向 UITableView 委托请求的单元格对象的指针。当您滚动表格时，它可能会在稍后重用，此时您的完成块实际上可能会被调用，因为下载 进程不是立即的。

如何处理？我会使用 UITableViewCell.tag 等属性来识别我在需要单元格时请求的确切图像，并且它是否与我在完成块运行时尝试放入该单元格的图像匹配。可能稍后会触发其他下载并覆盖标签属性。

【讨论】：

，问题出在 "cell.PinImageView.image=[UIImage imageNamed:@"[e-mail]"];"此 PinImageView 正在从数组中获取图像

【参考方案2】：

您必须通过将代码添加到操作队列上的 UICollection cellForRowAtIndexPath 方法的委托方法中来实现动态加载图像或延迟加载。

而且，如果你在 UI 上做一些你放在主线程中的事情，这里是另一个例子：

使用 SDWebImageManager 在 UICollectionView 中延迟加载图像